No matter how pretty they are, don't pick them! A picked trillium is a dead trillium, and these beauties are hard to find especially in such abundance. They like highly acidic soil and especially favor pine forests. Their red markings radiating out from the center and their pointed petals are to guide pollinators.
They are called trillium because they display three petals and three leaves. If you have some on your property you can dig them up and separate the rhizomes to encourage spreading but again do not disturb the wild ones!
What is one of your favorite spring wildflowers?