The snow of winter is important for vegetative landscapes in cold climates, including prairies. It has the effect of insulating the ground, keeping the heat in and cold out. Likewise, it also serves to keep the moisture in the ground. Even though the turf is frozen, if exposed, evaporation happens and the soils dry. And of course the newly deposited seeds from the previous year need moisture to geminate. Moreover, certain native wildflower seeds need to "stratify." Most milkweed species, for example, need a cold/moist stratification to encourage spring germination. The thawing/freezing of late winter/early spring has the effect of bringing them out of dormancy.
This Milkweed husk adds texture to the winter landscape. Moreover, these husks have been completely divested of their seed, meaning they've been distributed out into the prairie, waiting for the freeze/thaw of spring to bring the seed out of dormancy.
It is not unusual to see these "Galls" on Goldenrod stems. In winter they add a glossy/waxy texture to the prairie. These galls are called by the Goldenrod Gall Fly, which injects it's larvae into the stem of the Goldenrod plant, providing food and shelter until the larvae hatch. Other insect species are known to eat the fly larvae in the gall before they hatch.
The Goldenrod Gall Fly is quite small, not a good flyer, and lives a short life. They exist throughout all of North America.
This lone Compass Plant is much more noticeable in winter and provides nice contrast to the shorter plants.