Q:
When can you cut down the ratty-looking stalks and foliage of summer blooming perennials?
Justin Sinclair, Fairfield, CT
A:
Sydney Eddison, author of The Self-Taught Gardener, replies: Feel free to cut down any nearly leafless flowering stalk when the blooms have withered. This treatment is suitable for Siberian irises, bearded irises, Shasta daisies, hostas, garden pinks, coralbells, lilyturf, and daylilies. Also, it is safe to cut back the foliage of daylilies and bearded irises to about half when it begins to look disreputable.
Perennials with leafy flower stalks require a different treatment. As long as the leaves are green and healthy, they are manufacturing food and should be left alone. However, some leafy stems get so brown and battered that they cease to function effectively. Late in the season, the stalks of globe thistle, bee balm, hollyhocks, penstemon, and liatris become so tattered that they are of little use to the plant and diminish the look of garden overall. Cut them to the ground. You can cut down leafy stems as soon as you see new growth appearing at the base of the plant.
True lilies, which belong to the genus Lilium, are another story. Although their stalks and leaves are particularly ugly after flowering, you must not cut them down. You have to treat them like daffodils, allowing the stems and foliage to turn brown before removing them. To mask this defect, pair them with tall, perennial partners like ornamental grasses, which will hide them.
