Divide clumping plants now for a better spring garden
October 27, 2005
Victoria County
Master Gardener

Do you have some daylilies or society garlic that have just NOT been blooming like they should, although they appear lush and thick? They probably are overcrowded and really need to be divided. Now is the best time of the year to get it done.

It is recommended that plants that bloom in the spring and summer be divided in fall and winter. Those that bloom in fall should be divided in spring. Remember to divide during the season opposite their bloom time.

When we divide plants, it is referred to as vegetative propagation by division, or asexual reproduction. It is common with two kinds of plants - those with a clumping growth habit and bulbous plants (plants with specialized storage organs above or below the ground, including bulbs, corms, rhizomes, stolons, tubers and pseudobulbs.)

Cooler weather is coming and it is best to divide your daylilies, irises, society garlic, and other clumping perennials now. After being in the ground three to five years, they tend to crowd themselves out and will not perform as well. The soil fertility will probably be depleted and need some amendments. It is a good time to turn under the old mulch, add some compost, such as composted horse manure, and even add some bone meal. You may not notice better blooming right away the following year, but surely in the next few years.

It is recommended that gardeners prepare ahead of time to "divide and conquer" by watering the plants well the day before. Or divide after a recent rain. Also, know where you will place the divided plants and prepare that area before you start. The divided plants will have fewer roots and will require shallower holes than the originals. Be sure you divide and replant in enough time for them to become established before the possibility of the first freeze.

Also, it is a good idea to separate by sections and not transplant a whole bed, but to stagger the years you divide plants, so that everything is not newly transplanted. Do not try to transplant all of the new divisions in the same place, as your beds will be overcrowded. It is best to start a new bed or give the plants away to friends. Resist the temptation to replant them all unless you really need them.

Phlox or daisies are types of plants that start to look overgrown and need to be divided. You need to take aggressive plants, like bee balm, which actually start to get woody looking in the center and divide and replant them.

It is best to take the most vigorous side shoots from the outside of the clump of daisies or bulbine. Although difficult, it is best to discard the center of the clump or the mother plant. Replant clumps of about three to five shoots to the same depth below the soil from which they were dug. Be careful not to over-divide. If the clump is too small, it may not provide much color the next year.

Any plants that have roots or rhizomes that clump and spread can be pulled apart. Those that are connected can be cut with a sharp knife. A little treatment with fungicide is a good idea on any plants that have to be cut apart.

It is best to divide tough, large clumps by using two gardening forks. Dig all around the large clump, about 6 to 12 inches away, then lift and remove the whole root ball from the hole. Find a sparse place in the middle of the clump, and insert two gardening forks prying the handles apart to get two clumps.

When a root ball is very dense, and if this method doesn't work, use an ax or sharp saw. Be very careful, because you can hurt yourself a lot more than the plant with this method.

For dividing daylilies, which are tuberous plants, dig up the whole clump. Separate the fans. It is pretty easy to see and feel for the sections that come apart with little effort. The plants will do best if handled carefully, but if very large, you may have to use the "two gardening fork" method. If very large, repeat this division.

To replant the divisions, dig a large hole slightly shallower than the root ball and about 6 to 8 inches wider. Trim off all the dead parts and replace a section of the clump in the ground. Backfill with soil and tamp the soil in place. If you replant immediately, it keeps the plant from drying out. Mulch the transplanted daylilies lightly with about an inch of mulch and water thoroughly. Continue to water regularly until rooted in. You can also trim the leaves back to about 6 to 12 inches to reduce moisture loss.

A similar technique is used for dividing gingers, Louisiana irises, bicolor iris, fortnight lily, bulbine, society garlic, crinums and amaryllis (although amaryllis tends to prefer to be more crowded.) Some other common clumping plants are bromeliads, liriope and clumping bamboos.

If you have clumping container plants, such as overcrowded, out-of-control ferns or sansaveria, also called mother-in-law tongue or snake plant, you can also split them up to get several new ones. Start by removing them from the container.

Depending on how thick they are, you can actually cut them apart with a knife into two or three sections. Don't be afraid to hack away. Refill the new containers with a good soil-less container mix, placing the new clump in at the same depth as the original plant, and filling in with mix, pressing firmly to remove air pockets. A good watering will further remove air pockets in the soil. Keep in mind that divided plants won't immediately thrive after the trauma you have just inflicted on them, but in a couple of months you will have a beautiful plant again, multiplied by two or three.

When dividing plants, remember to think about a plan to share with friends, neighbors or other gardeners. Dividing and sharing your stock of prized plants or trading with friends is a fun part of perennial gardening and a good way to increase your stock in plants.

You are sure to see better blooms and more lush foliage after dividing - plus, you and your friends benefit from more plants. I love still having daylilies and amaryllis shared by special family members or friends from way back. This is just as invigorating to me as a gardener as it is for perennials to be divided at this time of year.