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Botany

09/02/20

Closed for Business

Closed Gentian (Gentiana andrewsii) was always a puzzle to me. When I first saw a picture of it in a field guide, I assumed that the photographer had simply taken the picture before the petals fully opened up. It was many years before I finally figured out what this plant’s deal was.

Closed Gentian (Gentiana andrewsii) grows in wet prairies, such as those at the Tall Grass Prairie Preserve near Gardenton, MB.

Back in 2004, while doing field work out at the Tall Grass Prairie Preserve, I had to walk past a few Closed Gentian plants to get to my research plots where I was studying pollinators. Every day I would think to myself, “when are those flowers finally going to open up?” Then one day as I walked past one, the whole plant vibrated. I paused, waiting to see what was going on. Suddenly, one of the fattest bumblebees I’ve ever seen pushed its way out of the flower and flew to another one, pausing briefly to nibble a small hole in the tip before pushing her way in. The proverbial light bulb went off in my head: the closed petals was this gentian’s way of preventing small insects that may be less-effective pollinators, from getting its precious nectar and pollen. Brilliant! I even came across a great video showing this behavior (https://www.youtube.com/watch?v=vDCrQzojP84).

Bumblebee visiting a Closed Gentian. (c) Gerrie Barylski. Used with permission.

Although there are many plants in the tropics that rely on very specific pollinators, this phenomenon is less common in Canada: most plants here rely on a wide range of pollinators-bees, flies, butterflies, moths and beetles-some over a hundred species. However, the only other type of pollinator besides bumblebees that can visit Closed Gentian are hummingbirds, which stick their long bills into the tip of the flower to access the nectar.

This model of Closed Gentian will be in the new Prairies Gallery.

I was so delighted with this plant that, many years ago, I asked our Diorama Artist to create a model of it, complete with a bumblebee butt sticking out, for a temporary exhibit on pollination I was doing. My plan was to eventually put this model in a permanent exhibit. At long last this lovely model will finally be on display in an exhibit on pollination, along with a hovering hummingbird, when the new Prairies Gallery opens up this fall.

07/08/20

Identifying a Ghost Plant

A week ago I posted a blog about a rare plant that I had been searching for in the West Hawk Lake area: climbing fumitory. Since then I’ve had several people ask me how to tell this plant (shown in in the picture above) apart from other similar species. In Manitoba there are only five species in the fumitory family and they are fairly easy to tell apart: two are rare and found in the southeast (climbing fumitory and Dutchman’s breeches), one is a weed from Europe (common fumitory) and the other two are fairly common in open woods and clearings in the boreal forest (corydalis).

Bleeding heart (Dicentra spectabilis). From Wikimedia Commons victorgrigas / CC0 .

All the plants in the fumitory family look somewhat similar to the common garden plant known as bleeding heart (Dicentra spectabilis), shown above. I think every child in the prairies has observed the heart-shaped pink and white flowers of this spring-blooming species before. I’ve got several in my yard that were probably planted when the house was built in the 1950’s. The leaves of species in this family are divided and almost fern-like in appearance. The flowers have four petals but they are irregularly shaped; that is, they are not all identical to each other, similar to snapdragons or orchids. The two inner petals are a different shape from the two outer petals. The outer petals may be mirror images of each other (e.g. Dutchman’s breeches, climbing fumitory) or dissimilar (corydalis). Although these plants are often lumped in with the poppy family (Papaveraceae), some sources (i.e. Flora of North America) consider them unique enough to be in their own family, the Fumariaceae.

Pink corydalis (Corydalis sempervirens) has pink and yellow flowers and long seed capsules.

Ecologically the plants in this family are poisonous (so no nibbling). Insects, however, enjoy the nectar found in the petal spurs. To get the nectar, long-tongued pollinators have to pry the outer petals apart, in the process rubbing up against the male (stamens) and female (pistil) parts of the flower, resulting in fertilization. However, some shorter-tongued insects have figured out that they can get the nectar just by nibbling a hole in the petal spur. See if you can find any of these cheat holes in the plants that you observe in nature.

Golden corydalis (Corydalis aurea) is a common herb in open areas in the Boreal Forest.

The seeds of the two corydalis species and Dutchman’s breeches have elaiosomes attached to them. These are fatty packets that ants like to eat. Ants pick up the corydalis seeds that pop out of the capsules when ripe, and carry them off to their nests where they chew the elaisomes off, leaving the seed onthe disturbed ground near the ant nest.

Here’s an identification key to the plants of the fumitory family (Fumariaceae) found in Manitoba. To use this key, select the statement that best describes your plant until you arrive at a species name rather than a number.

1. Plants are vines that climb up trees or rocks using tendril like-leaflets; petals almost completely fused together with a spongy texture………………………………………………………………. Climbing fumitory (Adlumia fungosa)
1. Plants are herbs not vines; petals fused only near the base, not spongy……………………………….…………..2

2. Both outer petals with a spur………………………………………….Dutchman’s breeches (Dicentra cucullaria)
2. Only one outer petal with a spur……………………………………….………………………………………………………….3

3. Flowers pink; fruit rounded, not splitting open; seeds lacking appendages…………………….………………..
……………………………………………………………………………………….…..Common fumitory (Fumaria officinalis)
3. Flowers yellow or pink with a yellow tip; fruit a long capsule that splits open; seeds with small appendages (elaiosome)…………………………………………………………………………………………………………………….…………..…4

4. Petals pink tipped with yellow; seeds to 1 mm diameter………..Pink corydalis (Corydalis sempervirens)
4. Petals yellow; seeds to 2 mm diameter……………………………………..Golden corydalis (Corydalis aurea)

07/03/20

In Search of a Botanical Ghost

Eighty years ago, Manitoba botanist Charles W. Lowe collected a plant from the West Hawk Lake area, not realizing that it would be the last time anyone would collect it in this province again. This June, I embarked upon a journey to see if that elusive plant was still hiding somewhere in Whiteshell Provincial Park.

West Hawk Lake was where the rare climbing fumitory (Adlumia fungosa) plant was found in 1940.

My scholarly journey commenced when I began working on a revised Flora of Manitoba; a book that will describe all the plants in the province. I searched through old papers, herbarium specimens and websites to compile a preliminary list of species for the province. Many new species had been confirmed or found since the publication of the last Flora of Manitoba in 1957, but there were also a few species that seemed to have disappeared. These plants are considered “historic” species: plants that had definitely been collected here in the past but not again for many decades. Are these species now locally extinct (i.e. extirpated) or are they still hiding in some remote area of the province? I’ve spent the last few years looking for some of them.

This is the only specimen of climbing fumitory (Adlumia fungosa) in the Museum’s collection; it was grown from seed in a Winnipeg garden. MM 34940

In some cases, mainly in Manitoba’s prairies, the habitats of the historic plants appear to have been destroyed by cultivation or construction activities. In other cases, the historic species’ seem to have been displaced by exotic plant species like smooth brome (Bromus inermis), which were introduced as a forage crop. However, the disappearance of climbing fumitory (Adlumia fungosa) was a bit of a mystery. My research indicated that it had been collected in the West Hawk Lake area, which is still largely intact. Why then was it seemingly gone?

While searching for more information, I discovered that this species is not common anywhere it occurs in the wild, in part because it is a biennial. That means its seeds germinate and grow a few leaves the first year, producing flowers and fruits only in the second year. Then it dies, remaining in the soil as a seed until its germination is triggered. But what triggers the germination? The references I found note that fires, windstorms and insect outbreaks that open up the forest canopy are likely triggers. But the soil cannot be severely damaged the way it often is with logging so apparently you don’t tend to see it in clearcuts. Plus, it likes rocky, acidic soils that stay consistently moist in places that are not too windy, and that have some trees or cliffs that it can climb up since it is a vine. In short, it appears to be adapted to thrive in very particular types of environments that don’t occur all that often anymore.

I searched for hours along the rocky, rooty Hunt Lake trail where this species may have been collected 80 years ago.

So, this year I decided to visit a recently burned area in the south Whiteshell, as well as the cliffs along Hunt and West Hawk Lake, to see if I could find this ghost species.  I was astounded at the beauty of the lake, which formed after an asteroid hit the earth in this spot about 100 million years ago. While I did find the rocky cliffs and moist soils that this species likes, I did not find the plant.  Some areas were likely too shady to trigger this plant’s germination, while in the burned area, there may not have been any seeds in the seed bank.

A rocky, recently burned area in the park where I searched in vain for climbing fumitory (Adlumia fungosa).

I began to wonder why Lowe found this species in the 1940’s. Since I couldn’t find any records of a large forest fire in the late 1930’s near West Hawk Lake, I thought that perhaps it was construction of the campgrounds and roads during that time that created a suitable opening in the canopy for this species. Decades of fire suppression, which improved greatly after World War II due to the use of aerial water bombers, have likely prevented the creation of the post-fire habitats in this area that the species needs. So even though humans have not changed this habitat by directly destroying it, we have changed it by altering the natural fire cycles that occurred before Europeans arrived. The presence of so many cottagers in the West Hawk and Falcon Lake areas means that any natural fires that do ignite will likely not be allowed to get anywhere near the recreational areas to protect human lives.

A close relative of climbing fumitory (Adlumia fungosa), pink corydalis (Corydalis sempervirens) grew in the recently burned area.

After so many years without disturbance, any seeds of climbing fumitory that were in the soil seed bank have likely died, and if that has happened, then this species may indeed be extinct in Manitoba. However, if an insect outbreak or windstorm damage occurs in the right spot, all may not be lost.  One thing I was reminded of during my trip is that the boreal forest is vast and, in many places, completely inaccessible to humans.  Climbing fumitory may still be hiding somewhere in this vast forest, waiting for some intrepid individual to stumble across it again.

06/01/20

Getting to Know Manitoba’s Wild Lilies

We share our world with billions of other organisms and they play a crucial role in our survival, providing the ecosystem services that keep us alive: making oxygen for us to breathe, filtering toxins from our water, and providing shade for us and our homes to name a few benefits. With so many cultural events being cancelled this year due to Covid-19, you may be planning on spending some time in nature this summer. Thus, now is an excellent time to learn to identify some of the beautiful wild plants that grow in our province.

Wild lily-of-the-valley (Maianthemum canadense) is a common species found on the forest floor.

As part of my Museum work, I have been writing an identification guide to all the vascular plants (i.e. ferns, conifers and flowers) in the province. Unfortunately, it is nowhere close to being done. However, in the interim, I can provide some information on how to identify some of the prettiest plants you will encounter in the prairies and forests of Manitoba: the lilies.

Autumn onion (Allium stellatum) can be distinguished from other wild onions by its pretty pink flowers.

Lilies are actually related to grasses. Both types of plants have leaves that are usually long and thin, typically with parallel veins (as opposed to net-like veins such as you see in a maple leaf). However, lily flowers are animal-pollinated so they have petals and are larger than those of wind-pollinated grasses, which lack petals. The main characteristic of lilies is that they usually have 3-6 floral parts unlike most plants, which have 4-5 floral parts (the dicots). Unlike their other close relatives, the orchids, which also have 3-6 floral parts, the petals of lilies are all the same size and shape; the petals of orchids are all slightly different, giving them an irregular shape like a lady’s-slipper. Irises are similar to lilies in that their petals are all the same shape but their flowers, at least in Manitoba, are all purple or blue (rarely white); most lilies in Manitoba have white flowers, less commonly yellow, pink or orange.

In this dried Museum specimen, you can clearly see the large bulb of this poisonous species, aptly named mountain death camas (Zigadenus elegans). Specimen #35061

There are only five wild lilies that are typically found in sunny, prairie habitats: Wood lily, prairie onion, autumn onion, eastern yellow stargrass and mountain death camas. One of these plants is poisonous. Can you guess which one? The word “death” in the name kind of gives it away, no?

The white flower of nodding trillium (Trillium cernuum) dangles below the three-parted leaves.

Lily species that grow in sunny habitats have narrow leaves, to reduce their sun exposure. In contrast, the lilies that grow in forested habitats tend to have wider leaves to better capture the dappled light that occurs on the forest floor. Most of the forest lilies have white flowers (sometimes with invisible ultraviolet (UV) patterns that bees can see), because white is more visible in a dark environment like a forest floor. Fairy-bells, Solomon’s-seal and false Solomon’s seal (Maianthemum spp.) are among the most common species in Manitoba. In the southeastern forests you will also find the highly attractive nodding trillium with its leaves in three parts and dangly white flower, and the lovely yellow clintonia.

The pretty flower cluster of yellow clintonia (Clintonia borealis) develops into bluish berries by mid summer.

Below is an identification key to the 21 wild lilies of Manitoba. To use this key, decide which of the paired statements best describes your mystery plant, then go to the number that is after that statement. Continue selecting statements until you arrive at a species name. You may have to use a second key (indicated in brackets after the group common name) to identify the plant to its species. To determine the scientific (Latin) name of your species, go to the list at the very end of this blog. You can double check that you identified the plant correctly by searching for an image and description of the species on the internet. Enjoy hunting for Manitoba’s lovely lilies this summer!

Having floral parts in 3’s is a key character of plants in the lily family like this eastern yellow star grass (Hypoxis hirsuta).

Key to the Lilies of Manitoba

1. Leaves arising from close to the ground or nearly so (basal)……….……………………….…………………2
1. Leaves alternating or in whorls on the upper part of the stem…..……..…………………….…..………….7

2. Fruit a blue berry; leaves wide and thick…………….……………………..…..…………….. Yellow clintonia
2. Fruit not fleshy; leaves narrow and thin …………………….…………………………….………………………….3

3. Flowers bright yellow; ovaries (unripe fruits) densely hairy……….………. Eastern yellow stargrass
3. Flowers not bright yellow; ovaries not hairy…………………………….……………………………….….………4

4. Flower stalks all arising from a single point on the stem (umbel); leaves strongly onion-scented……………………………………………………………………….……. Wild onions (see species key below)
4. Flowers arising from various points along the stem (raceme); not onion-scented…….………..……5

5. Plant arising from a bulb; petals 7-10 mm long………………………..……… Mountain death camas
5. Plant not arising from a bulb; petals less than 5 mm long………………………………..…..…….…………6

6. Stems smooth; seeds lacking appendages; far northern Manitoba………………..…… Small tofieldia
6. Stems covered in sticky hairs; seeds with appendages…………………………..……..….. Sticky tofieldia

7. Leaves in whorls of 3 or more…………………………………………………………..….…….….……………………8
7. Leaves alternating on the stem.………………………………………………………….…….………….……………..9

8. Upper leaves in a whorl of 3; flower white, nodding…………………………..……….… Nodding trillium
8. Upper leaves in whorls of 3 to 11; flowers yellow or orange, erect……………..………….…… Wood lily

9. Flowers at the tip of the stem (terminal), singly, in clusters of 2-4, or on a stalk (raceme).………10
9. Flowers in leaf axils, singly or in clusters of 2-4….…………………………………..…………………………..12

10. Flowers in racemes……………….………………………… False Solomon’s seals (see species key below)
10. Flowers single or in clusters of 2-4 at stem tips……………………………….…..…………………..………..11

11. Flowers 1-2 (3), white; fruit an orange berry………………….…….………………………………… Fairybells
11. Flowers 1-4, yellowish; fruit a capsule…….…………………………… Bellworts (see species key below)

12. Flowers in clusters of 2-4; fruits dark blue berries………..………………………. Giant Solomon’s seal
12. Flowers single; fruits orange to reddish berries……………. Twisted-stalks (see species key below)

Key to the Bellwort (Uvularia) species
1. Leaves wrapping around the stem, finely hairy, not covered with bluish powder; fruit a dry                                      capsule less than 15 mm long………………………………………………..…………..… Large-flowered bellwort
1. Leaves not wrapping the stem, not hairy, covered with bluish powder; fruit a dry capsule over                                    15 mm long…………………………………………………………………………….…..……….. Sessile-leaved bellwort

Star-flowered false Solomon’s seal (Maianthemum stellatum) is flowering in many riverbank forests right now.

Key to the False Solomon’s-seal (Maianthemum) species
1. Leaves 2-4; flowers arising from a simple stalk (raceme)……………….………………………………………2
1. Leaves more than 4; flowers arising from a simple or branched stalk (panicle)………………………..3

2. Flowers with 4 petals and 4 stamens; usually 2 flowers arising from a single spot……………………..                            …………………………………………………………………………………………………………….. Wild lily-of-the-valley
2. Flowers with 6 petals and 6 stamens; 1 flower per spot………………. 3-leaved False Solomon’s Seal

3. Flowers arising from a dense, branched stalk; flower stalks <1 mm long; ripe berries red………….. ……………………………………………………………………………………………………… Large false Solomon’s Seal
3. Flowers arising from a simple stalk; flower stalks 6-12 mm long; ripe berries black………………… ……………………………………………………………………………………..…… Star-flowered false Solomon’s Seal

Key to the Twisted-stalk (Streptopus) species
1. Leaves strongly clasping, edges smooth or toothed, not hairy; floral stalk strongly jointed and                         bending at an abrupt angle; petals strongly upturned…..……………….. Clasping-leaved twisted-stalk
1. Leaves stalkless or slightly clasping, edges hairy; floral stalk not strongly jointed; petals only                             slightly upturned…………………….……………..……………..………………….. Midwestern rose twisted-stalk

Key to the Wild Onion (Allium) species
1. Leaves egg- to lance-shaped, shrivelling before flowering; fruit a 3-lobed dry capsule… Wild leek
1. Leaves linear, not shrivelling before flowering; fruits a capsule only slightly lobed……………..……2

2. Flower stalks shorter than flowers, leaves round in cross section, hollow……………….. Wild chives
2. Flower stalks equalling or exceeding the flowers; leaves flat or channelled, not hollow………..…..3

3. Bulb covered with net-like fibers; flowers white; stamens not longer than petals..… Prairie onion
3. Bulb not covered with fibers; flowers pink; stamens longer than petals……………… Autumn onion

Common and Scientific Names of Manitoba’s Wild Lilies

-Autumn onion – Allium stellatum Fraser ex Ker Gawl.
-Clasping-leaved twisted-stalk – Streptopus amplexifolius (L.) DC.
-Eastern yellow stargrass – Hypoxis hirsuta (L.) Coville
-Giant Solomon’s seal – Polygonatum biflorum (Walt.) Ell.
-Large false Solomon’s seal – Maianthemum racemosum (L.) Link
-Large-flowered bellwort – Uvularia grandiflora Sm.
-Midwestern rose twisted-stalk – Streptopus lanceolatus (Ait.) Reveal
-Mountain death camas – Zigadenus elegans Pursh
-Nodding trillium – Trillium cernuum L.
-Prairie onion – Allium textile A. Nels. & J.F. Macbr.
-Rough-fruited fairybells – Prosartes trachycarpa S. Wats.
-Sessile-leaved bellwort – Uvularia sessilifolia L.
-Small tofieldia – Tofieldia pusilla (Michx.) Pers.
-Star-flowered false Solomon’s seal – Maianthemum stellatum (L.) Link
-Sticky tofieldia – Triantha glutinosa (Michx.) Baker
-Three-leaved false Solomon’s seal – Maianthemum trifolium (L.) Sloboda.
-Wild chives – Allium schoenoprasum L.
-Wild leek – Allium tricoccum Ait.
-Wild lily-of-the-valley – Maianthemum canadense Desf.
-Wood lily – Lilium philadelphicum L.
-Yellow clintonia – Clintonia borealis (Ait.) Raf.

05/04/20

Beautiful Parasites (and a couple ugly ones too!)

It is pretty well known that plants differ from animals due to their ability to make their own food using just carbon dioxide, water and sunlight through a process called photosynthesis. But some plants are a bit lazy and figured “why should I make my own food like a sucker when I can just steal some from my neighbor?” Thus, the strategy of plant parasitism was born.

The lovely Labrador lousewort (Pedicularis labradorica) typically parasitizes dwarf birch (Betula pumila) shrubs in the boreal forest.

The secret to being a plant parasite is to produce modified roots, called haustoria. Rather than collecting water and minerals from the earth like normal roots, haustoria pierce the roots or stems of other plants and tap into their vascular systems. The haustoria suck up the sap from the parasitized plants, obtaining water, minerals and the product of photosynthesis: sugar. The parasitized plants are weakened but not usually killed, unless stressed for other reasons.

The evolutionary journey to parasitism was not always completed; while some species became full parasites (=holo-parasites), such as dodders (Cuscuta spp.) and dwarf-mistletoes (Arceuthobium spp.), others are only partial parasites (=hemi-parasites). Hemi-parasites still produce green leaves and are capable of photosynthesis, unlike the holo-parasites, which no longer perform any photosynthesis at all. Through their haustoria, hemi-parasites obtain mainly water and minerals from the parasitized plants, which means they can grow in habitats where they might normally be at a competitive disadvantage in terms of their ability to obtain enough soil resources.

Yellow owl-clover (Orthocarpus luteus) is a fairly common plant hemi-parasite in prairies and parklands.

There are many species of hemi-parasites that grow in the wilds of Manitoba but they are not all related. World-wide, parasitism appears to have evolved independently at least 12 times. In this province there are three families that contain parasitic plants: the Morning-Glory, Sandalwood, and Broom-rape families. The Morning-glory family contains the aforementioned dodders; plants that twine up the stems of other plants and steal sugar from them. In Manitoba the entire dodder genus is on the noxious weeds list although none of the species are terribly common. In fact, two species of dodder that typically infect native plants, buttonbush dodder (Cuscuta cephalanthi) and hazel dodder (C. coryli), are considered critically imperilled in Manitoba. Common or swamp dodder (C. gronovii) is slightly more abundant, but not a major weed.

The tiny common dodder (Cuscuta gronovii) wraps its stems around those of native plants like stinging nettle (Urtica dioica).

The Sandalwood family contains the most common parasites in the province: the holo-parasite dwarf-mistletoe, and the hemi-parasites pale comandra (Comandra umbellata) and false toadflax (Geocaulon lividum). Pale comandra typically grows in dry prairies, parasitizing a wide variety of common plants like asters and roses, while false toadflax is found in our northern forests living off of woody plants like bearberry (Arctostaphylos spp.) or asters.

Like all plant parasites, pale comandra (Comandra umbellata) will not grow in a garden setting unless an appropriate host plant is nearby.

All plants in the Broom-rape family including paintbrushes (Castilleja spp.), owl’s-clover (Orthocarpus luteus), louseworts (Pedicularis spp.), eyebrights (Euphrasia spp.), cow-wheat (Melampyrum lineare), and false foxgloves (Agalinus spp.) are hemi-parasites. Many of the broom-rapes have colourful, fragrant, two-lipped flowers that attract and support many pollinators, typically bees and butterflies. In Manitoba, 15 of the plants in this family are considered rare (ranked as critically imperilled, imperilled or vulnerable by the Manitoba Conservation Data Centre). Gattinger’s agalinis (Agalinis gattingeri) and rough agalinis (A. aspera) are both extremely rare and legally protected under the national Species-at-risk Act, 2002 and the provincial Endangered Species and Ecosystems Act, 2018. The rare and unusual-looking broomrapes (Orobanche spp.) are holo-parasites on wild asters, possessing no leaves, just coppery-coloured stems and large white, yellow or purplish flowers. Many of these rare parasitic plants grow in our endangered native prairies, dependent on the wild plants that grow there, which are themselves increasingly rare due to exotic species encroachment, habitat loss and climate change. Clearly, being a parasite is not as carefree as it sounds.

The holo-parasite, clustered broom-rape (Orobanche fasciculata) can be found on sandy soils in places like Spruce Woods Provincial Park.

Now that you know they exist, be on the lookout for these, sometimes lovely, sometimes ugly, groups of free-loading plants.

04/09/20

Tree Tales: Canada’s Threatened Trees

Canada’s trees have developed some resistance to native diseases and insect pests. However, climate change has been facilitating more forest damage. For example, the native Mountain Pine Beetle (Dendroctonus ponderosae) used to be held in check because it was killed by extremely cold winter temperatures, which occur less frequently now than they used to. Additionally, in the last 125 years, the importation of live trees and untreated wood from other continents has brought in many pests that now threaten not just urban trees, but the integrity and survival of our wild forests as we know them. Likewise, the accidental importation of North American diseases and pests, such as the Pinewood Nematode (Bursaphelenchus xylophilus), threatens forests on other continents. The stories of just three threatened Canadian tree species are recounted below.

American Chestnut (Castanea dentata)
In the hardwood forests of eastern Canada and the United States, massive 35-m tall American Chestnut trees once grew. They were an excellent source of timber and produced edible nuts enjoyed by both people and wildlife. In some areas it was estimated that one of every four trees was a chestnut. Then, in 1904, the New York Zoo brought in livestock of Japanese Chestnut (Castanea crenata) trees that were infected with the fungus known as Chestnut Blight (Cryphonectria parasitica). This fungus damages the cells that transport water and sugar through the trees, eventually causing them to starve to death. The spectacular American Chestnuts had no natural resistance, unlike Asian chestnuts, and the disease quickly spread. By the 1940’s, four billion chestnut trees were dead, and their niches became occupied by other trees such as maples (Acer spp.) and oaks (Quercus spp.). American Chestnut still survives as a shrub sprouting from old roots but eventually all individuals succumb to the disease. In Canada, it is endangered and protected by the Species-at-Risk Act, 2002. However, there may be a way to bring this species back using modern technology: trees that appear to be blight-resistant have been bred by inserting a novel gene from wheat.

American Chestnut leaves and fruits from the Manitoba Museum’s collection. MM F-38.

American Elm (Ulmus americana)
The beautiful fan-shaped American Elm tree became one of the most popular urban trees in North America; in the city of Winnipeg alone, there are more than a quarter of a million. These trees are also common in the wild, growing in hardwood and mixedwood forests along with poplars (Populus spp.), ashes (Fraxinus spp.), Manitoba maples (Acer negundo) and spruces (Picea spp.). In 1928 elm wood containing spores of Dutch Elm Disease (DED) (Ophiostoma novo-ulmi), a type of fungus, arrived in untreated wood destined for the furniture industry in Ohio. The fungus was spread by both native and introduced bark beetles, which tunnel under the bark of elm trees. By 1989, the fungus had destroyed 75% of all North American urban trees. DED reached Manitoba in 1975 but summer pruning bans, prompt removal of infected trees, prohibition of elm firewood transportation and treatment with pesticides and a vaccine helped Winnipeg protect its trees. Winnipeg is now the home of the largest surviving urban elm forest. However, unless these efforts are sustained, losses will mount and more trees will die.

The beautiful Pembina Valley is full of wild American Elm and ash trees.

Ash (Fraxinus spp.)
As DED began decimating North America’s elms, many communities began planting Green (Fraxinus pennsylvanica) and Black Ash (F. nigra) instead. However, these species are now threatened (Black ash was place on Canada’s endangered species list in 2018) due to the accidental importation of pests from other continents in untreated wood products (sound familiar?). The Emerald Ash Borer (Agrilus planipennis) arrived in Michigan from Asia in the early 1990’s, and was first sighted in Manitoba in 2017. This beetle feeds on the inner bark of a tree, eventually strangling it. Another pest, the Cottony Ash Psyllid (Psyllopsis discrepans), a type of jumping tree louse, was introduced from Europe, arriving in Winnipeg in 2017. The Psyllid damages the leaves of ash trees rather than the bark. This double whammy of pests will likely kill most of Winnipeg’s ash trees in the next decade and forever alter our wild ash forests. The negative impact on wildlife that rely on ash trees for food and shelter will be huge. Fortunately, some individual trees appear to be more resistant to the Emerald Ash Borer, and can help us breed insect-resistant stock.

Manitoba’s Green Ash is being decimated by the introduced Emerald Ash Borer.

How to Save a (Trees’) Life

There are many things we can do to help protect our trees.

1. Slow the Spread
Follow all biosafety protocols regarding importation of any plant or plant product. Buying locally grown trees and nursery plants, and locally produced wood mulch rather than imported products is the safest option. Consider buying and refinishing antique furniture, and using reclaimed or recycled wood for woodworking and construction projects instead of new wood. To be safe, don’t transport ANY firewood; burn local wood only.

2. Reduce the density
Planting monocultures of the same species may look nice (I love those green elm tree “tunnels” as much as the next person), but it is a recipe for disaster. Planting a greater diversity of tree species lets them “socially distance” from one another, reducing the likelihood of disease transmission and catastrophic tree losses within a short period of time. If you lose a tree in your yard, replace it with a different species than the ones surrounding it.

Planting more poplar (Populus spp.) (left) and pine (Pinus spp.) (right) trees will increase the diversity of our urban forests.

 

3. Improve tree health
Remember to prune trees properly when they need it, adhering to any relevant pruning bans. If you don’t know what you’re doing, contact a professional arborist (tree doctor) for help. Regular watering of young or vulnerable trees, and banding trees to reduce cankerworm infestations will also help your trees stay healthy.

4. Support scientific research
Scientific research that was started 43-years ago at an arboretum at Penn State may hold the key to saving ash trees as some appear to have natural resistance and can be used for breeding resistant stock. In Canada, the University of Guelph has been leading a breeding program for DED-resistant American Elm trees. The National Tree Seed Centre in Fredericton, New Brunswick stores seeds of Canada’s native trees, which can be used to breed resistant plants. In fact, the public is being encouraged to collect and send them wild ash seeds for their seed bank. But public support for research that doesn’t appear to offer any immediate benefit, is not always forthcoming. Real life is not like a Hollywood movie; scientists can’t conjure up cures to diseases overnight. It takes years of research to come up with solutions to new problems. Let your political representatives know you support publicly-funded science.

Trees provide us with so much-oxygen, shade, beauty, wildlife to admire and even food-that we need to give something back. You can report sick trees in Winnipeg by calling 311, the Canadian Food Inspection Agency or the Emerald Ash Borer hotline at 1-866-463-6017. If you lost a tree to disease or the tree-pocalypse storm in October 2019, consider planting a new one as soon as you can. Many Winnipeg greenhouses will even deliver plants right to your door this year. If you would like to see a tree planted on a city-owned boulevard or park, you can ask the city of Winnipeg to plant one.  Remember the best time to plant a tree was 20 years ago. The second-best time is now. Enjoy your neighborhood trees this spring!

03/20/20

If a tree falls in the forest

We humans tend to think that diseases affect only animals but plants suffer from them as well.  Diseases are caused by microscopic animals (like parasitic worms), fungi, bacteria and viruses and they affect animals, plants, fungi and even some species of bacteria (viruses that infect bacteria are called bacteriophages).  But it’s not just microorganisms that parasitize species; larger organisms do too. Some fungi are parasites of other fungi and some plants are parasites of other plants.   One good example that you may have encountered while going for a walk in the woods is the Lobster Mushroom (Hypomyces lactifluorum). This species of fungus parasitizes other fungi, often the mushrooms of milk-caps (e.g. Lactarius), distorting the shape and resulting in the bright orange colour.  Although some people enjoy eating these mushrooms, they could be poisonous if the mushroom that was parasitized was poisonous.

Fungi are sometimes infected by fungal diseases. This is a mushroom cap infected by the fungal parasite Hypomyces lactifluorum. You might recognize it by its common name: Lobster mushroom. Source: Wikimedia Commons

Another common parasite you may have encountered is Dwarf Mistletoe (Arceuthobium spp.).  Mistletoes parasitize trees such as white spruce (Picea glauca), causing strange broom-shaped branches, often called “witches-brooms”.  Mistletoes are actually flowering plants that cannot photosynthesize.  Instead, they have modified roots that can tap into the vascular systems of other plants to steal their sap.  To disperse their seeds, the fruits build up hydrostatic pressure, and then shoot the seeds into the air at speeds of up to a spectacular 80 km per hour!  The seeds are covered in a gluey substance, which helps them stick to the bark of trees.  The germinating seed sends its roots into the tree bark instead of the soil.

Dwarf mistletoe (Arceuthobium americanum) is a plant parasite on trees like white spruce (Picea glauca). Source: Wikimedia Commons, J. Schmidt 1977

Parasites and diseases are what population ecologists call density-dependent causes of mortality; factors that only affect an individuals’ survival when populations are at high densities.  Other density-dependent factors affecting plant survival include: competition for resources, such as water, light and soil minerals, and intense herbivory (usually by insects).  In general, density-dependent causes of mortality are biotic, that is, caused by other organisms.  Density-independent factors of mortality are usually abiotic (not alive) or environmental: forest fires, drought and volcanic eruptions that bury vegetation in lava are a few examples.

There are plenty of plant parasites and diseases that evolved right here in North America.  However, most native plants have evolved methods to resist these organisms to some degree so it is not always fatal to the plant, unless it is in a weakened state.  During droughts for example, trees are much more likely to die of a disease.  Since the colonization of North America occurred, species of diseases that were not native to this continent have been accidentally introduced, typically with dire consequences.  In my next blog, I will be discussing how three species of native Canadian trees (American Chestnut, American Elm, and Green Ash) are being negatively impacted by introduced diseases, and how we can change our behaviour to protect our forests, both wild and urban.

02/18/20

A BRIEF HISTORY OF INDIGENOUS AGRICULTURE

One of the most significant contributions that America’s Indigenous peoples have made is with respect to agriculture. Many of our most beloved foods (e.g. chocolate, potatoes, corn) are native to the Americas, being initially cultivated or domesticated by Indigenous farmers.

These flowers will produce cacao “beans” which are used to make one of the world’s most loved foods: chocolate (Theobroma cacao)!

Ancient Agriculture
Indigenous agriculture has a long history with the most recent archaeological evidence suggesting it has been practiced in the Americas for at least 10,000 years, almost the same time length of time as in the Fertile Crescent of the Middle East. There were five agricultural centers of origin (i.e. places where multiple species were cultivated or domesticated) in the Americas: three in South America and one each in Central and North America (Table 1).

Table 1. Crop plants cultivated or domesticated in the Americas by Indigenous peoples.

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Cereals & pseudo-cereals: Amaranth, chia, goosefoot, knotweed, little barley, maize (corn), maygrass, quinoa, sunflower and wild rice.

Legumes & nuts: American chestnut, black walnut, Brazil nut, cashew, common beans (green, black, pinto, navy, etc.), hickory, lima beans, peanut, pecan, scarlet runner beans and tepary bean

Roots & tubers: Arrachacha, arrowroot, camas root, cassava, hopniss, jicama, leren, mashua, oca, potatoes,  sunroot, sweet potato and yacón

Fruits: Acai, avocado, blueberry, chayote, cherimoya, cranberry, feijoa, guava, huckleberry, papaya, passionfruit, peppers, persimmon, pineapple, prickly pear, raspberry, squash,  strawberry, tomato and tomatillo

Spices, beverages & flavours: Achiote, chicle, chocolate, coca, maple, tobacco,  vanilla and yerba mate

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The Andes was where the earliest crops (e.g. potatoes (Solanum spp.) were domesticated about 10,000 years ago. Corn (Zea mays) and squash (Cucurbita spp.) domestication began in Central America 8,700 years ago and beans (Phaseolus spp.) shortly after. In the eastern U.S., agriculture was being practiced 3,800 years ago.

Prickly pear cactus (Opuntia) produces an edible fruit.

Spread of Indigenous Crops
Crops that were part of the “Eastern Agricultural Complex” in the southeastern U.S. included a variety of nutritious seed plants such as sunflower (Helianthus annuus), goosefoot (Chenopodium berlandieri), bottle gourd (Lagenaria siceraria), marshelder (Iva annua), little barley (Hordeum pusillum) and squash (Cucurbita pepo). Other domesticates that followed include ragweed (Ambrosia trifida), pigweed (Amaranthus spp.), and knotweed (Polygonum spp.).  After ~200 BCE  (before common era) corn, beans and squash from Mexico were brought to this region and cold-tolerant varieties (e.g. Northern Flint) bred. The productivity of corn was so high that the traditional seed crops fell out of favour and were gradually abandoned. Sunflowers are the only crop plant left from the original Eastern Agricultural Complex that is still grown today. The other species have largely reverted to their wild state. Some of these species are considered “weeds” in croplands today even though they are still edible.

Sunflower (Helianthus annuus) is the only crop plant from the “Eastern Agricultural Complex” that became a modern crop plant.

Agriculture Spreads to the Northern Plains
Most people are surprised to find out that Indigenous people were practicing agriculture in the Dakotas and Manitoba in the early 1400’s. In 1986, Manitoba Museum Curator Dr. Leigh Syms unearthed evidence that corn, beans, squash and sunflowers were being grown as far north as Lockport during that time (http://www.mhs.mb.ca/docs/mb_history/31/firstfarmers.shtml).  These three plants were traditionally planted close together with the beans climbing up the corn stalks and the squash helping suppress weeds. Raising plants in this manner improved the fertility of the soil as beans harbour special bacteria that turn gaseous nitrogen into a form available to all plants (ammonium or nitrate). Together these three plants were the foundation of a healthy, vegetarian Indigenous diet. Sunflowers, often called the fourth sister, were typically grown along the edges of Indigenous fields, and provided an additional source of fat and protein.  Climatic changes which resulted in a shorter growing season and population losses due to diseases introduced after European contact in 1492, may have resulted in the abandonment of the cropland in Manitoba.

The three sisters-corn, bean and squash-were typically grown together in Indigenous fields.

Columbian Exchange
After Europeans arrived in the Americas, crops from the “Old World” (e.g. wheat, barley, oats) were brought here while American crop plants were transported to Africa, Asia and Europe; this process was known as the Columbian Exchange. Sometimes the new American foods were embraced readily (e.g. beans) but others were not, particularly those in the nightshade family (e.g. tomatoes, potatoes and peppers). In Europe, nightshade plants are mainly poisonous rather than edible so people were suspicious of them. In France, people initially rejected the potato (they thought it caused leprosy) but King Louis the 16th was convinced by the agronomist Antoine Parmentier that it was a good food plant to grow. Apparently, Parmentier had potatoes planted in the Kings’ gardens and then set guards around them to prevent thefts (although the guards were told to accept bribes). This reverse psychology apparently worked and after some people got their hands on the potato, its cultivation spread. Many American crops are now an integral part of European, African and Asian food culture. However, introduction of these new foods did cause some problems.

Potatoes (Solanum tuberosum), like the ones growing in this Manitoba field, are now the world’s most popular vegetable.

The Importance of Indigenous Food Culture
The knowledge of how to prepare American foods did not always accompany the food, possibly because Europeans of that time period were generally disdainful of Indigenous knowledge, customs and food culture. Unfortunately, this attitude ended up causing a lot of unnecessary deaths.

People in warmer parts of Europe and Africa readily adopted corn because it was so much more productive than other crops. But after doing so a strange new disease began affecting poor people who were relying mainly on corn for food. This disease is pellagra, a condition that causes dermatitis, diarrhea, dementia and eventually, after four or five years, death. Physicians were confused about this new diet-related disease because they noticed that even though Mexicans ate a lot of corn, they rarely got pellagra. The answer to this puzzle was in Indigenous food culture. Corn was often softened by soaking it in an alkaline solution. This softened corn, known as hominy, is then eaten as is, or dried and ground to make masa, the flour used to make tortillas and tamales among other things. This process, known as nixtimilization, increases the bioavailability of niacin (vitamin B3) and tryptophan in corn. Pellagra is caused by a deficiency in niacin and tryptophan in the diet. In Europe, Asia, Africa and even among poor non-Indigenous people in the southern U.S. , people were just drying the corn, grinding it up and cooking it into dishes like cornbread or polenta. Eaten in this manner, with no other foods containing niacin in the diet, pellagra is the result. Another aspect of Indigenous food culture that was not taken to heart was the custom of eating corn with niacin-containing beans, resulting in a balanced diet.

Eating in the Indigenous manner, either nixtamilized or with beans, corn can be the basis of a nutritious vegetarian diet.

Food Culture and Reconciliation
Racism and the intellectual and cultural arrogance that accompanies it, has caused tremendous human suffering. Colonization and the discouragement of traditional Indigenous agricultural practices and cooking, resulted in the near loss of ancient varieties of crop plants such as quinoa, as well as the memory of how these foods should be grown and prepared. It is heartening to see Indigenous peoples embracing their gastronomic legacy by planting three sisters gardens, writing cookbooks featuring pre-colonial foods (e.g. The Sioux Chef’s Indigenous Kitchen, Cooking with the Wolfman, and tawâw) and opening innovative restaurants (e.g. Ishkode Indigenous Pop-up https://aptnnews.ca/2019/10/25/indigenous-pop-up-showcases-traditional-eats-in-a-modern-world/). Part of reconciliation is simply accepting that Indigenous culture is valuable. Another part is supporting the efforts of Indigenous peoples in keeping their culture alive. Food has a way of bringing people together so maybe the path forward is to sit down and share a meal together.

01/20/20

The Perils of Plant Parenthood, Part 2 – Wildlife

Many plants use the wind to disperse their seeds. But what if a plant lives somewhere that isn’t very windy? How do they encourage their children to “launch”? Many plants decided to take advantage of animals’ mobility. One way plants do this is by growing little hooks or stiff hairs on the fruits that readily catch onto the fur or feathers of an animal when they are ripe. The fruits are carried for possibly hundreds of kilometers before getting rubbed off. The fruits of many North American prairie plants are adapted for transport on bison fur.

The seeds of wild licorice (Glycyrrhiza lepidota) have hooked bristles that catch readily on the fur of passing animals, like bison.

But what if you live somewhere where there aren’t a lot of big, hairy animals. As it turns out there are ways to get smaller creatures to transport your seeds as well. You do it by producing a substance that the animals find irresistible: fleshy fruits.

Plants that live on the forest floor have it pretty tough because there is very little wind and there usually aren’t big herds of animals hanging around. So some early flowering plants, including violets, bloodroot and Dutchman’s breeches, adapted to use insects to disperse their seeds instead. The seeds of these plants have fatty structures attached to them called eliosomes. After the seeds fall off the parent plant, ants carry them to their nests, remove the eliosomes and then abandon the seeds.  The plant seeds sprout readily in the disturbed habitat.

The seeds of violets (Viola) are dispersed by ants, which eat the fatty structures attached to them.

Plants with fruits that ripen late in the year often rely on flocks of migratory birds for dispersal. Birds are particularly good seed dispersers because they lack teeth, typically swallowing fruits whole. In bird stomachs, the fleshy part of the fruit is digested but the tough seeds usually excreted intact. In fact, the seeds of many plants need to pass through the guts of animals before they will even germinate. However, some fruits are toxic to mammals (like rodents) but not birds.  This is because mammals tend to chew the seeds as well as the fleshy parts, killing the baby plant. For that reason, berries that birds can eat are not always safe for people!  Therefore, make sure you have correctly identified and researched the toxicity of any fruit before you eat it.

Some fruits, like bittersweet (Celastrus scandens), contain toxins to discourage mammals from eating them.

There’s one more creature that plays a huge role in the dispersal of seeds: people. Humans are by far the best seed dispersers ever. We don’t just move seeds a few kilometers; we move them to entirely new continents, creating the exact kinds of conditions the plants like to grow in. Humans like to think that we domesticated plants and forced them to do our bidding, but it is entirely possible that it was the other way around; perhaps it was the plants that domesticated us.

Wheat (Triticum) plants hookwinked a certain group of mammals into dispersing their seeds all across the planet: humans.

 

01/06/20

The Perils of Plant Parenthood, Part 1 – Wind

Just like all creatures, plants want to reproduce themselves. But they typically don’t want their offspring hanging around for too long, eating all the food in the fridge and drinking all the beer. But plant babies living on the land can’t move on their own, so how is an exasperated plant parent going to get their children to leave the nest?

Instead of producing swimming babies like algae do, the very first land plants produced special structures called spores. These spores, which grow into tiny plants, are small enough to be carried away easily by the wind, just like dust. For about 80 million years or so, the only plants on land were species that produced spores: club mosses, horsetails, ferns and mosses.

The first land plants, including ferns, produced single-celled spores instead of multi-celled seeds.

About 390 million years ago in the mid-Devonian, a new group of plants evolved that were capable of growing very quickly. They are known as the seed plants, and they have dominated life on land for many millions of years. But what exactly is a seed anyway and how is it different from a spore? A spore consists of only one cell; it’s basically a naked baby. For that reason, spore-producing plants aren’t very good parents; they just boot out their kids with nothing to eat and no clothes on. A seed on the other hand consists of three things: a baby, a bottle to feed the baby and clothes to protect the baby.

The first seed-producing plants were the gymnosperms (which means “naked seed” in Latin). They produced multiple babies in structures called cones. But the seeds of these cone-bearing plants are quite heavy compared to the spores of ferns, and initially they may have fallen right under their parent. Plants will obviously not grow very well in the shade of their parent, so any kind of structure that would help the seed move a little further away was advantageous. That’s why many cone-bearing plant seeds evolved a thin wing that increases wind resistance and helps the seed glide further away.

The seeds of Jack pine (Pinus banksiana) cones have tiny wings to help them float away from the parent tree.

The development of seeds was a real game changer because plant babies were way more likely to survive with a food source. There was just one problem: animals. Seeds represented a new source of food for them and they eagerly indulged.

Around the same time mammals evolved, in the Jurassic period about 160 million years ago, yet another group of plants evolved that had an advantage over the cone-bearing plants: they protected their young by enclosing them in fruits. In many species, the fruit also functions as a mode of transportation, essentially a kind of baby carriage. In habitats that are open and windy, like grasslands, many plants continue to use wind to disperse their babies. The elaborate shapes of the fruits (many functioning like parachutes), enables the seeds to fly for much longer distances than the simple gliding seeds of the cone-bearing plants.

The seeds of many aster plants, like goat’s-beard (Tragopogon dubius), have fruits shaped like parachutes, which help them fly.

What if a plant lives somewhere that isn’t very windy though? What do they do? Stay tuned for part 2 of “The Perils of Plant Parenthood” to find out.

 

Dr. Diana Robson

Curator of Botany

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Dr. Robson obtained a Master’s Degree in Plant Ecology and a Ph.D. in Soil Science at the University of Saskatchewan. She has been working at the Manitoba Museum since 2003, conducting research mainly on rare plant and pollination ecology.