Kathleen Brown

One of the best ways to get more plants is to propagate from your existing plants. One of the easiest techniques is dividing the roots of the plant. Once your “mother” plants are several years old, it’s good to divide them anyway to stimulate more vigorous growth, so you can plant more or give them away to friends and neighbors.

Fall is the best time to divide, but early spring works too. Just don’t wait until too late in the season or you’ll spoil the main plant’s bloom. Woody perennials such as Salvia (from one main woody stem) won’t work. Instead, pick the clumping type of perennials or those that send out runners to multiply. Then, using a pointed shovel or turning fork, dig all around the clump to remove it from the ground. One of the best tools for dividing the clump is a Hori Hori knife, a Japanese tool that looks like a heavy-duty knife but with a serrated edge on one side. You can also use a pointed trowel or a small folding tree saw. If the clump is, say, about 12” square, divide it into half, and one half back into the hole. Add some compost and water well. The second half can be divided into half or thirds and these can be placed elsewhere in the garden. Just be sure that each portion has a good clump of roots. Iris need to be divided every few years. These are slightly different because the Iris foliage comes from rhizomes. When dividing Iris, dig up the clump, then separate the rhizomes off the mother plant. When replanting the rhizomes, lay the root parallel to the ground, leaving it partially exposed.

Monarda, or bee balm, is another great example. This tends to travel via runners in a mannerly fashion and “naturalizes” itself in large patches. In this case, it isn’t necessary to dig out the whole clump. Instead, just cut “plugs” out of the patch. Dig your trowel or Hori Hori knife into the clump, then raise a section and cut around the edges to loosen. The hole in the patch will fill in quickly.

Some Asters, on the other hand, can be quite invasive in their desire to multiply via runners! Just cut out the undesirable new plants and pull the runner back as far as you can. Replant or give away the new plants.