Within the next couple of weeks many eastern hardwood forests will be blanketed with white trilliums (Trillium grandiflorum, Liliaceae). Each spring this particular patch in southeast Michigan covers several thousand square feet. These individuals grow on a north-facing slope above a floodplain. While common above this elevation, they are completely absent in the floodplain itself.
White trilliums grow in these dense clusters because of two weak dispersal methods. First, they create spreading networks of underground rhizomes that give rise to many clonal plants. Second, seeds are dispersed over a slightly greater area mostly with the help of ants. Neither of these mechanisms cover a great distance, resulting in these concentrations of plants.
These perennials are known for their large, white, three-petaled flowers that turn pink with age. Some flowers are pink from the time they open, and double flowers sometimes occur. From personal observations it seems that the pink form may occur in under 1% of this population, but I have yet to find a double-flowered form.
The flowers of these spring ephemerals will be gone by mid-May, and those that are successfully fertilized will produce small fruit and seeds.