The composition of the groundlayer varies from site to site due to the fluctuating water supply. In some cases, the development of the groundlayer is delayed until mid-August. A few late summer bloomers include calico aster, spotted jewelweed, green-headed coneflower, and late goldenrod. Spring blooming perennials are at a distinct disadvantage due to seasonal flooding. From year to year the composition may change, depending on how different species respond to flooding.
Mature trees can reach very large sizes.
Silver maple and cottonwood trees may measure a circumference of 17-20 feet. The canopy spread is proportionally large. A typical forest may have only about 85 trees per acre because of these large dominants. Many trees have multiple stems as a result of damage to trunks by ice and flood-carried debris. Low densities of seedlings and saplings are typical in a wet forest.