Monthly Article by Cate White,
San Joaquin County Master Gardener
Now that fall has arrived with warm days and cool evenings, the time is perfect to survey and renew your garden. This is the best time of year to plant shrubs and perennials, so they can begin to establish their root systems before the weather gets cold. Take stock of your yard, looking for for plants that need refreshing or replacing. You may notice some perennials are overgrown and need to be divided. This is a perfect way to fill in blank spaces with new plants without having to purchase them.
There are several methods of division, depending on the type of plant. Plants that bloom in the spring or early summer are best divided now, while plants that are fall-blooming should be divided in the spring.
The easiest plants to divide are those that grow from bulbs or corms, like daffodils, freesias and grape hyacinths. Over the years, these tend to grow into large clumps, which can simply be dug up, shaken to remove the soil, and then divided into individual units. Replant them at the depth they were originally planted. Even small ones can grow into new plants, although they may take a year or two to bloom.
Also easy to divide are plants growing from tubers or tuberous roots, such as dahlias and decorative sweet potato vines. Again, dig them up once they form clumps, and divide them into individual tubers. Each tuber should have an eye. Tubers can be kept in perlite or clean sand over the winter, and then planted in moist well-draining soil in the spring.
Bearded iris and ginger plants grow from rhizomes that also need occasional dividing. Dig them in late summer or early fall, and either break or cut them apart. Each section should have a set of healthy leaves. Older pieces at the center of the clump may be shriveled and dry without leaves and should be discarded. Cut leaves and roots down to about 6 inches and let the cut ends dry several hours before replanting. Plant them just below the soil level.
Some plants, such as those in the yucca and aloe families, produce offsets or “pups” next to the original plant. Dig up the original plant plus the offsets, then pull or cut the offsets off along with its roots. Usually, the original plant on is old and spent, and can be thrown out. If you expose open cut areas, let them harden over for a few days before replanting. Plant the offsets so that their bases are at ground level.
Last are the plants that can be divided by crown division. These are plants such as Shasta daisy, coreopsis, yarrow, aster, daylilies, huechera, and others that expand over time into bushy clumps. They can be dug up and divided into several smaller plants by pulling apart or by using a sharp knife or shovel. Make sure each section has ample roots. Gently prune back the tops and remove any damaged roots. Replant in damp soil, and make sure to water them in well.
Engaging in this process, you may feel like you are manhandling your plants so severely that they won’t survive. Take heart. Plants are hardier than you think, and most will actually thrive once they’re divided. As plants age and grow crowded, their vigor diminishes. Dividing them can actually give them new life.