Also the petals spread outward from the base in Trillium ovatum , in contrast to the ascending petals of T. grandiflorum . In Alberta this species was recently rediscovered in Waterton Lakes National Park, but it is not known elsewhere in the province. May be accompanied in the forest by salal, violets and ferns. Yellow violets often flower at the same time. Once the flower is pollinated the petals change colour from white to pink, perhaps as a signal to pollinating insects to search for food elsewhere.
Petals often wither early, but the sepals are persistent.
When the ripe, green-coloured capsules first open, the seeds are in a glutinous mass. The seeds have an oily appendage, attracting ants which carry them to their nests. In this way ants are an important dispersal agent for the plant. Western trillium seems to respond to favourable conditions in some years. Size of the flower and fruit are greater, and more seed is produced, when conditions are just right.