If your agapanthus, daylillies or coneflowers haven’t bloomed well in a while, dividing them might give them the boost they need.
Diving perennials also is a great way to control a perennial that has grown too large for its space and to create more plants for your garden.
Fall is a great time to divide perennials. A cool and cloudy day is best for the job.
First, trim about one third to one half of the plant’s leaves. This reduces the effort the newly planted divisions need to put into maintaining foliage.
The easiest way to divide a plant is to dig up the entire plant — roots and all. Dig deeply so that you get the entire root ball. Lay the plant on the ground or on a hard surface. Some perennials, such as yarrow, are easy to divide; they nearly separate themselves when you dig them up. Others, such as daylillies and agapanthus, have tightly bound roots, and you will need a tool and some muscle to separate them.
You want to end up with divisions that are about the size of a plant you would buy and plop into your garden. You don’t want teeny weeny bits.
You also want divisions that are healthy with succulent roots. Pitch or compost the dried up and wood parts of the plant.
To separate the tough perennials such as daylillies, use a sharp knife or shovel, garden fork or even a pruning saw. Try to cut between, not through, healthy shoots (Do your best. Perennials are amazingly forgiving and resilient). You definitely shouldn’t hack away at the plant; try to make one clean slice from the base of the plant through the roots.
Plant the new divisions as soon as you can, at the same depth as the original plant, and water them well immediately. Protect them from the sun for a few days. Our winter rains are coming soon so the youngsters shouldn’t need additional water, but keep an eye on them, and don’t let their new abode dry out. You can always put several inches of mulch around them to keep the soil moist, but keep the mulch away from the plant’s stems.
Joan Tharp is a University of California Cooperative Extension master gardener. She lives in San Mateo. She can be reached at firstname.lastname@example.org.
Our friends at Santa Clara County Master Gardeners will show you how to divide perennials 10 a.m.-11 a.m. Nov. 5 at their Palo Alto Demonstration Garden, 851 Center Drive, Palo Alto. To register and for more information visit http://cesantaclara.ucdavis.edu/?calitem=141685.