The plant is found from Ontario in the north to northern Georgia in the south and from Michigan in the west to Nova Scotia in the east.

The white petals have wavy edges and a central red to reddish purple splotch at the base of the flower.

Populations of T. undulatum often have a large number of seedlings with a single leaf since individuals remain in the one-leaf stage for relatively long periods of time.

As of October 2021[update], Plants of the World Online (POWO) lists 8 synonyms for Trillium undulatum.

In addition, numerous abnormal forms have been reported,[15] including variants with multiple whorls of bracts, enormous sepals, or four or more parts (instead of the usual three), the latter being somewhat common in T. undulatum.

[16] The range of Trillium undulatum extends from Ontario in the north to northern Georgia in the south and from Michigan in the west to Nova Scotia in the east.

Although the soils that support it have low base saturation, this species was found to have relatively high levels of calcium, magnesium, and especially potassium in its foliage.