My native trilliums (the beautiful white ones that have now faded to purple) are thriving in my woodland garden. I would like to know when the best time is to dig up a clump to share with a friend.
According to Michael Leigh’s Grow Your Own Native Landscape (Olympia, WA: Native Plant Salvage Project, 1999), dividing Trillium is difficult because you must “dig deeply to ensure minimal damage to roots and rhizomes, take special care not to break the stems, and transplants may die back before reappearing the following spring.” According to April Pettinger’s Native Plants in the Coastal Garden (Whitecap, 2002), “Trilliums do not like to be transplanted, so if you decide to move them to another site, be prepared for them to take several years to flower again.” My personal experience suggests that taking as much of the soil around those rhizomes as possible will give the plant the best chance of success, and I think early fall is the best time, although I don’t find any source that specifies a time of year. Right after bloom may be fine too, as it is the recommended time for division according to the American Horticultural Society’s Plant Propagation (DK Publishing, 1999).