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How to Divide Crowded Perennials
At some point, a garden full of healthy, thriving perennial flowers will become crowded. When this occurs, growth is likely to slow and blooming may even stop. Respond to such crowded conditions by dividing perennials, and you will invigorate the plants and create new ones.
Follow these gardening tips when dividing perennial flowers.
When to divide perennial flowers
Telltale signs that it’s time to divide include crowded conditions and slowed, sluggish growth for plants that were once doing well. Perennial flowers that have more than five or six strong stems coming from their base are also often ready for division.
Generally, it’s best to divide perennial flowers in the spring or fall when the weather is mild. Avoid dividing a plant that is flowering or budded up—instead wait until the blooms fade. If a plant will bloom all summer, hold off on dividing until fall.
What perennial flowering plants to divide
Many perennials respond well to division, but it is best to check on the particular plant you want to divide before doing so. Some plants that appreciate being divided and replanted include aster, astilbe, iris, bee balm, bellflower, candytuft, some lilies, black-eyed Susan, blanket flower, bleeding heart, canna, chrysanthemum, coreopsis, Joe-pye weed, Echinacea, true geranium, phlox, hosta, rosemary, lamb’s ear, ornamental grasses and yarrow.
While many perennial flowering plants respond well to division, the procedure is still essentially surgery. Prepare the plants for transplant shock by watering the bed well the day before with a solution of vitamin B-1, according to package directions. Also prepare ahead of time the ground or containers where you will be placing the excess plants.
How to divide perennials
1. With a sharp garden spade, dig 4 to 6 inches away from the base of the plant around all sides. Slide the spade underneath the root ball and work it loose, lifting the entire clump, if possible. If it is too large, cut it apart with the spade or a shovel.
2. Shake off excess soil, and pull out any weeds or stray plants so you can get a good look at the root ball.
3. Some plants will naturally separate into clumps that you can easily pull apart with your hands. Other plants will need to be cut into sections, which is best done with a sharp, sturdy knife, or a saw if the root mass is especially tough and fibrous. Cut into even sections.
4. While you work, remove and discard any unhealthy plant parts, including sections that have browned or have squishy roots.
5. Avoid shock by transplanting your newly divided perennial flowers quickly and watering well with a fish fertilizer solution. Keep the area well-watered, but not soggy, while the plants re-establish themselves. You will know they have done so when you see new growth.
6. If you wish to share divisions that result from dividing perennials with a fellow gardener, protect the plants by misting the root zone with water and wrapping in burlap or a plastic bag.