Nothing conveys innocence and purity than lily-of-the-valley. Convallaria majalis is one harbinger of spring most of us anticipate, with its dainty fragrance and stalks of bell-shaped flowers. It loves the shade and grows in clumps in moist, well-drained soil rich in organic matter. It does not do well in bright sunshine or dry, compacted soil.

Convallaria majalis is the Eurasian species. The North American native is Convallaria majlis montana.

Don’t be fooled by the term lily. This cute plant is actually part of the asparagus family. And don’t be fooled by its seemingly “cute” appearance. Every part of the plant, from roots to stems to flower to berries is highly poisonous. Its phytochemicals act on the heart like those found in the digitalis of foxglove.

While it looks and smells sweet it is a thug. It spreads through rhizomes, meaning it travels rapidly underground. It is difficult to keep in check. It would be best planted in a pot, either as a container or buried in the ground where the roots can be kept in check. 

This is a very long way of saying that while fall or early spring might be the best times to plant, lily-of-the-valley isn’t fussy. Give it shade and moist, healthy soil and it will do fine.

Here are other resources you might look at.
http://www.gardening.cornell.edu/homegardening/scene2835.html
https://extension.psu.edu/programs/master-gardener/counties/luzerne/news/2021/may-birth-flower-lily-of-the-valley
https://extension.psu.edu/lily-of-the-valley-convallaria-diseases