By Zan Tomko
The prairie is nature’s dynamo, generating energy through the growth of plants and animals to support an immense and complex ecosystem. As you walk through the 20-acre Bennett-Johnson Prairie at the Arboretum, planted in 1968, emerging flowers pop up through last year’s flattened forbs and grasses to begin the cycle of energy again.
The vast number of species in a prairie — and the food web generated by them — develop over the course of the summer following an elegant sequence, so plants and their respective pollinators each have an opportunity for reproduction. It’s an easy walk through the prairie now and you’ll notice that the level of the blooms rise as the season progresses.
Early summer starts off with a low whirr of tree frogs and toads and builds to a crescendo of critters in the bio-mass created for survival. Spiders and low-flying insects are a food source for emerging amphibians and toads.
Dew catches on the gossamer webs created by sheetweb and dwarf weaver spiders to catch even smaller insects. These insects are pollinators of the early season flowers.
It’s all up from here, starting with 6-inch violets in spring all the way to big bluestem in the autumn. Close to the ground, these different violets are some of the first prairie forbs to bloom.
A prairie is a name for a section of fertile land made up of forbs and grasses, with the availability of water determining what types of plants that will grow there. All prairie plants can survive uneven moisture through their extensive root systems.
Erratics are boulders or rocks that have traveled with glaciers or glacial outwash hundreds of miles to become embedded in the prairie soil. Samples of erratic rocks form the retaining wall along the roadside edge of the prairie. Lichens — seen here on a granite rock — can find a home almost anywhere.
The prairie is also home to shrubs and low-growing, tough, small trees, including gooseberry and choke-cherry.
The acorns of the bur oak are the largest of any North American oak species and feed so many in the prairie food web. While gophers rule the dry, sand or hill prairies, eastern grey squirrels follow the oaks and acorn abundance from the forest to the prairie savannas.
The dramatic bur oak is a pioneer tree species of the prairie, tough enough to fend off the roots of prairie forbs and grasses as well as the traditional climax species of the prairie, the buffalo.
Oaks have thick bark that protects the vital cambium layer in the event of a fire. The development of the prairie system was dependent on fire and grazing buffalo for renewal. The Minnesota Dakota peoples are part of the Buffalo Nation, where the prairies, the people and the buffalo were interconnected and dependent on each other.
At the top of Bennett-Johnson Prairie, an oak sapling has grown from the parent tree. Oaks produce many more acorns than needed for reproduction, because — like this one that sprouted up near the retaining wall — they won’t all make it to maturity.
We also live from the bounty of the prairie through the development of agriculture, land-grant universities, the expansion of transportation and the marketplace which all spring from the riches offered by the prairie.
Zan Tomko is an artist, horticulturalist and a Minnesota Master Naturalist.