Dividing established perennial plants is essential for keeping them healthy and looking great. They can be divided in the spring, but autumn is a premium time because gardeners and plant-lovers have more time in the fall, says C.L. Fornari, a garden writer, speaker, and consultant.
In the spring, there are beds to prepare, mulch to spread, annuals and vegetables to plant, Fornari says. In the fall, the garden is fresh in your mind. You remember that the yarrow was so large it overwhelmed the spot.
She cautions, however, that watering into November may be required if the necessary rain doesnt fall, because newly disturbed root systems need weekly watering for at least eight weeks. Roots also need six to eight weeks to develop before the ground freezes in northern areas.
Most perennials will benefit from division every few years. If a plant doubles the size of its crown every yearsuch as with Shasta daisies, New England asters, and pink coreopsisit should be divided every other year, Fornari says. Other plants, such as daylilies and ornamental grasses, should be divided when the crowns grow more than 18 inches in diameter, otherwise theyll be too difficult to dig up. Some perennials, such as bleeding heart, babys breath, and peonies, never need dividing.
Proper preparation will make the process go more smoothly and help the plants adjust better after the division. Water them thoroughly a day or so before you plan to divide them. If youre replanting the divisions, prepare the area where they will go. Plan to divide the plants on a cool cloudy day, especially if the garden is in full sun so the divided plants wont be stressed by a hot, drying sun. All you need to divide most perennials is a good garden shovel and a sharp knife.
Ignore any drawings you might have seen that show two pitchforks crisscrossing and pulling the plants apart scissors fashion. This does not work, Fornari says. Use your shovel to dig the entire clump out of the ground, and then cut the clump with the shovel or a sharp knife. When lifting the plant from the garden, keep as much of the root intact as possible. If the plant is very large, Fornari suggests cutting off pieces of the outside edge, the newest growth, and throwing away the older middle.
After dividing the plants, either pot them or replant as soon as possible. If you cant replant right away, keep them in a tray or bucket filled with water. Water them well after planting, and be sure to apply a thick layer of mulch to help them get through the winter.
Perennial plants are an excellent investment, both in money and friendship. Use the divisions to plant more of the same, rather than buying new plants, or exchange them with a friend who has different varieties. Either way, your investment blossoms.