From time to time, I receive e-mails from readers of Yard and Garden Planning asking various gardening questions. This month, I’d like to round out the year with a sampling of the questions (and answers) that I’ve received. Have a wonderful holiday season and a very happy New Year.
When is the best time to remove spent blooms from perennials — should it be throughout the growing season or only at the end of the season?
This depends on the species. With some plants, you’ll lose a lot of bloom if you wait until the end of the season. With others, such as threadleaf coreopsis, shasta daisies, salvia, and delphiniums, you’ll want to remove the blooms promptly after they fade in order to get another flush of bloom later in the season. With purple coneflowers and black-eyed Susans, removing spent blooms really doesn’t affect how long they bloom. Many gardeners cut off faded blooms to keep their gardens looking tidy, such as with peonies, daylilies, and iris, or to prevent the plants from self-seeding.
What is the best time to divide perennials?
Some plants do better if they are dug and divided in spring, other prefer later summer. The rule of thumb that I learned when I first started gardening was: If they bloom in spring, divide them in late summer (this includes plants like salvia, asters, phlox, ornamental grasses, chrysanthemums and purple coneflowers). If they bloom in summer and fall, divide them in the spring (this includes plants like iris, peonies and bleeding hearts).
Some plants can be divided nearly anytime — spring through fall — except when they are blooming (hostas and daylilies are two good examples here).
How do you keep coleus indoors through the winter, but keep the stems from becoming weak and leggy?
Coleus and other annuals, such as geraniums, begonias, and impatiens, become tall and leggy because of the limited amount of light they receive compared to what they are used to outdoors. Instead of bringing in large plants, take stem cuttings. This way you will start with a much smaller plant that will adapt to indoor light levels. To root a cutting, place paper toweling in the bottom of a plastic clamshell (the type that has a hinge on it) container from the grocery store. This container has openings for ventilation and the lid retains moisture and humidity. Fill about 1/3 full of perlite. Water the perlite well. Cut a 3-inch piece from the end of a stem and remove the lower leaves. Dip the cut end in rooting powder, if desired, and insert the cutting into the perlite up to the first set of leaves. Close the lid and place the container in indirect light for about 3 weeks. Plant the rooted cuttings in fresh potting soil once the roots are about 1 inch long.