I recently planted several trillium plants (grandiflorum and erectum) that were shared from a friend’s garden. They have been planted under a large linden tree where they get early morning sun but are in fairly dense shade the rest of the day. They have started sending up new shoots and have about an inch to an inch an a half of new growth. I’m not really sure how to address this to increase the chance of them surviving the winter. Happy for any advice you can give. Thanks!
The best time to plant and divide trilliums is when they are dormant, so that would be late summer and early fall in southern Ontario. You seem to have timed it right. Also, you have planted them in an ideal spot, as they grow best in their natural habitat i.e. under deciduous trees. They thrive in rich organic matter and require full to partial shade and moist, well-drained soil with a neutral to acidic pH. Some sun will be tolerated but they should be protected from the very hot sun of summer. Trillium species vary in hardiness, with a range of USDA Hardiness Zones 4 to 9. They are not affected by any serious pest or disease problems.
Some trilliums will produce off shoots when their roots/rhizomes are cut into, such as when lifted from your friend’s garden. Furthermore, the weather we’ve been having this year has been unpredictable. In September we had warmer temperatures and there was rain, which must have encouraged your plants to grow new shoots. Really all you can do is let nature take its course and hope that they will survive the winter and reappear next spring. It should be noted that they do need a dormant period in order to appear next spring. They will die back once the weather gets cooler. Add a layer of leaves now to the area where your trilliums are planted to help keep them cool and protected and to encourage the winter rest they need.