Q: I’ve had a patch of wild daylilies on the edge of my yard for 23 years, but lately there are many fewer blooms. Is it time to divide them? — Rose Mast, West Milford, NJ
A: Wild daylilies (Hemerocallis fulva) don’t need division. But garden daylilies do need to be divided from time to time because they form clumps that eventually become congested and stop blooming well. Very fast growing varieties like ‘Stella d’ Oro’ need to be divided about every third year, and early spring is a good time for this. Instead of forming clumps, wild daylilies send out rhizomes (underground stems that look like thick roots) that grow into open spaces, forming large patches. They don’t become congested and will bloom well without division indefinitely — if they get about six hours or more of direct sun a day. Yours may have become too shaded to bloom well; nearby trees could have filled in and blocked out the sun. A little tree pruning might admit enough direct sun to bring back the flowering. Or maybe it’s time to remove a whole tree or two. Early spring, before trees leaf out, is an excellent time to do this work, too. But if you prefer to leave the trees in place, you have two options. First, you can do nothing and just live without the flowers. Even without blooms, wild daylilies make a superb ground cover — virtually carefree, with thick grasslike foliage. They are almost unequaled for choking out weeds and holding the soil in place on steep slopes and stream banks. Your second option is to replace your daylilies with more colorful shade-lovers like hostas. The largest kinds, especially, are almost as good at choking out weeds and retaining the soil on a steep slope, but they have more attractive foliage, in blue, green, gold, and bicolors. And hostas bloom wonderfully in the shade. Spring is a good time to plant them. Before planting hostas or anything else where daylilies have been growing, you should dig up all the daylilies to a depth of about a foot. Carefully remove every last scrap of daylily root that you can. Then apply about an inch of compost over the soil, plant the hostas you have chosen, and mulch the bed with any weed-free organic mulch you can get your hands on (shredded leaves, composted bark, or grass clippings). If tiny sprigs of daylily resprout from pieces of root you have missed, dig them out as soon as you see them.