One of the pleasures of spring is taking stock in your garden: Which perennials are ready to be doubled (or even tripled)? To address your spring bloomers, you must wait until fall. But now is the time to divide fall bloomers so that before summer arrives, they will have ample recovery time.
Dividing plants not only benefits your garden, it also gives older perennials a chance to rejuvenate and thrive once again. Doing this chore isn’t necessary every year; depending on the species, every two to five years is sufficient.
In picking candidates for division, focus on perennial clumps that have been producing fewer flowers, or flowers with hollow, dead centers. Chrysanthemums, asters, cannas, ornamental grasses, coneflowers and astilbe will all appreciate the extra attention.
A few days before you divide them, give your plants extra water, and make sure to prepare the bed, so you can pop the new divisions into the ground right away. If possible, pick an overcast day for the task. Dig around the plant, giving it a four- to six-inch berth. Remove the root ball of the entire clump and separate out sections as gently as possible.
To separate very tangled roots, greater force might be needed. Pry the roots apart with two garden forks placed back to back. Try to wriggle rather than tear. Use a kitchen knife judiciously to pull apart the toughest clumps. Finally, make sure you get your new divisions into the ground that day, and provide plenty of mulch and water to help them settle into their new location.