March is here, the best time to start multiplying and dividing in earnest – multiplying some of the native plants we already have growing in our backyard forests, using a plant propagation method known as division. Basically, the method consists of digging up all or part of an existing plant, dividing or separating the root ball into two or more parts, and then planting the individual pieces where they will have room to grow into “new,” full-size plants. Sometimes the pieces are just sections of roots or rhizomes. Other times they include both roots and leaves. A sharp knife, hand clippers, or even a small pruning saw will work to cut roots, root masses, or rhizomes into separate pieces.
To find out more about division, I exchanged emails with my longtime friend Mitch Blanton, retired Western Washington University Gardener, who has an amazing perennial garden at his house in Bellingham, Washington. (His garden won Best in the City – twice!) I wanted to know when and how to divide native plants like Inside-Out Flower (Vancouveria hexandra). Mitch told me that division is an “immensely satisfying way of multiplying a garden’s assets” and that this method of plant propagation has been his primary method of expanding his perennial garden.
Mitch wrote, “I think March is the best time for division — April is good, too. Many plants like Vancouveria can be dug in a clump the size of a dinner plate, or larger. If the root ball is a thick mass of roots, I use a meat cleaver or spade to chop it into multiple pieces. Some perennials make multiple crowns, each with a distinct root system. I soak the ball in a bucket of water and wash all the topsoil off so that I can carefully untangle the roots.”
Update–June 15, 2024: Mitch starts the divisions in pots with his normal garden soil and then plants them after the roots have taken hold and the plants have begun to sprout and leaf out.
Mudding In
I asked him how he plants the divisions, and he wrote, “A technique I consider very important for success is known as ‘mudding in.’ When replanting the divided plants, I dig a hole at least three times the volume of plant material/root ball, fill it with water, put in the plant, and then as I backfill it with topsoil, I mix the topsoil and water forming mud. With this, the plant shouldn’t need any more water for weeks. Basically, you can’t overwater on planting.”
Which Plants Can be Propagated by Division?
Some plants, including Salal and Oregon Grape, cannot be propagated by division, but many can. According to Grow Your Own Native Landscape by Michael Leigh, native plants that divide well include ferns, sedges, rushes, and bulrushes. Some of the plants that grow well from rhizome cuttings include Inside-Out Flower, False Lily of the Valley, Pacific Bleeding Heart, Deerfoot Vanilla Leaf, Wild Ginger, Fireweed, and False Solomon’s Seal. These native plants, if acquired in one-gallon pots from retail nurseries, typically cost around $10 each — all the more reason to start multiplying by dividing.