Not sure what type of ivy. Invasive?
Some sort of ivy climbing most of the trees, younger leaves look as if they just have 3 points while the more mature leaves appear to have 5.
I would suspect small camas based on the size and shape of the petals.
Trilliaceae (Melanthiaceae in book, terminal solitary infl, lvs and perianth in 3s, whorled lvs)
Melanthiaceae: 1a
Trillium: 1b, 2b, then no option for red/purple petals.
I believe it's Trillium kurabayashii
Tree close to Mary's river,
starting to flower