Trilliums inhabit deep and moist woodlands across the North American Temperate Zone. Some, since they are not known as great map readers, seem to have even wandered into Eastern Asia.
In California we have several species of these Lily relatives. The flower in Spring, and produce seeds in Summer in berries. Most of them have seeds dispersed by ants, though that gets harder to demonstrate if the berries actually ripen - they simply fall off at that point!
To collect actually ripe seeds of Trillium ovatum such as shown above on our land, the seed filled berry needs captured in a mesh bag before it actually ripens.
This last weekend was our weekend for bagging the berries on this species in our yard. The other local species was collected a week or two ago: Trillium chloropetalum. Our son is a fierce defender of these little plants and actively helps seek them out and protect them. Here he is heading back up our hill after helping with bagging of the Trillium berries!