PlantFiles: Painted Trillium
Trillium undulatum

It is native in upstate NY, found at the higher elevations, often near tall pines. It blooms on our property in about the third week of May, usually after a warm rain. It develops a bright red seed in mid-summer that looks something like a fruit. The deer sometimes eat the flowers and the seed, so this trillium is not widespread. In addition to being known as almost impossible to transplant, it's also very slow to germinate from seed, taking 2 or more years to sprout and then up to 4 years to grow large enough to flower.

these plants are spectacular and they tend to grow everywhere here in Vermont. i saw one plant with six leaves!

From William Cullina's Growing and Propagating Wildflowers of the United States and Canada:

Quoting: Painted Trillium is a striking species, with pure white, upward-facing flowers with a prominent triangle of red-purple in the throat that bleeds up along the veins of the petals to the tips. The fruit is a distinctive, smooth oval berry with a pointed tip. Painted Trillium is a common species in northern New England and southeastern Canada, but is very difficult to grow in cultivation, needing consistently moist, cool, acid soils and especially prone to rots in less than ideal conditions. I include it because this is a species often wild collected and sold as "nursery propagated", but you can be 99 percent sure that no nursery is really successfully propagating it. Please enjoy it in the wild".