The Range of Prairie Plants--Natives of Edmonton, Alberta

blanket flower Gaillardia aristida

"I know that plant!" I was 1200 miles almost due north of home, in Edmonton, Alberta at a Botanical Society meeting. I had never been that far north in Canada. There, a native garden at the Shaw Conference Centre featured plants important to the local Cree tribe. And most were plants I knew from Colorado. See blanket flowers, asters, monarda in Edmonton, below and in my "grow local natives" Denver Post article.

aster, Symphyotrichum laeve

Puzzled, I thought about it.

Grasslands stretch across central North America from Texas to Alberta. We call them prairies or the plains or steppe, but until settlement they were one continuous whole, from the forest edge in Kentucky to the base of the Rocky Mountain forests, from the southern end of Alberta's boreal forest to the Gulf of Mexico.

grasslands of the plains

Of course the plants change, especially as the plains get drier going westward, but some plants can be found from one end of that huge region to the other, and many have immense ranges.

North to south, the changes in plants are gradual. If you draw a line north from Texas to Alberta, the south is drier and warmer and the north cooler, with a much shorter growing season, and in those cool conditions, effectively moister. Some plants drop out and others replace them, but some species are found across that whole area.

My eye was drawn to the familiar and there they were, plants I really like, cherished by the Cree as well.

yarrow, Achillea millefolium

Not far north of Edmonton, the grasslands end and northern forests begin. The plains plants of  Colorado do not grow under the forest, although likely forest plants from Colorado can be found in Alberta's forests. An example is the fireweed, below, in the Alberta garden, it is a Colorado forest plant as well.

fireweed, Chamerion angustifolium

When change in climate or soil is gradual, you can have the experience I did, of seeing old friends displayed as important local natives in a distant place.

They won't be identical. Below the obvious similarity lie traits that adapt them to local conditions. If it is cooler or the frosts come in August not September, local plants have to survive these conditions. Thus, my Colorado blanket flower in Alberta would likely grow more slowly than an Alberta blanket flower, expecting more heat and not getting it. Similarly, the Alberta blanket flower will finish flowering and develop its seeds by the time of Alberta's average frost, while the Colorado plant growing there might initiate new buds too late, because in Colorado the killing frost comes later. Sometimes botanists recognize those differences as different species or varieties, but when change is gradual, as in the plains, often no distinction makes sense.

big clump of Monarda fistulosa, wild bergamot

Recognition of local adaptation and gradual change has led to scientific debate about "how local" the native wildflowers for, say, a replanted prairie, ought to be. If they are from almost that exact area, surely they are locally adapted. As you get farther away, their local adaptation isn't correct and not only might they die, if they survive their non-native genes might change the local population.

I'm not a strong advocate of planting only local plants (genotypes in the jargon) in a native reserve. Natural selection needs genetic diversity so that whatever the conditions, some individuals have the right genes. In central North America especially, there is terrific variation in growing conditions between weeks, months and years. A diverse population is going to do better than a uniform one when (not if) the rare event occurs.

At one time, all of the region was continuous grassland with essentially no barriers. Herds of bison wandered on irregular paths across the region. Seeds that stuck into their hair might go hundreds of miles before falling out, bringing a plant from far away into the local population. Likewise birds or winds carried the occasional seed or pollen grain to a new home across the plains.

coneflower, Echinacea angustifolia

Our world is one of change. Global climate change and variable weather patterns but also plowing grasslands, creating roads, building towns and cities modify the environment of native plants. Two hundred years of observing plants (and animals) has repeatedly shown that diverse populations are the most resilient to change, whatever the change is.

So my view is that while local is good, diverse is better. Pragmatically that is replanting with seeds from across the street and adding a handful purchased from a reliable native seed company. If a nearby population no longer exists, the best response is not to despair but to plant diverse enough seed that over time local adaptation can develop.

But more important, my wish, for everyone across the vast plains of central North America, is: plant and cherish native plants. As the Cree garden photographs show, they are gorgeous.


Comments and corrections welcome!

Full disclosure: I said I'd never been as far north as Edmonton. Not precisely: in July 1998 I crossed from Alaska into the southern corner of the Yukon Territory for an afternoon, but I remember lakes and rocks from that trip, not plants.

References
USDA Plants website: plants.usda.gov. to see continuous distributions for these plants.

Kathy Keeler

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