Spring Plant Division – Murdering … er, Making Multiple Copies of Your Existing Plants
March 12, 2017
There are three methods widely available to home gardeners for creating new plants: starting from seed, starting plants from cuttings, and plant division. Every plant does best with one or two of these methods, depending on that plant’s characteristics. For example, starting seeds is great for annual plants like vegetables. Taking cuttings often works best with woody plants like shrubs and trees. Fast-growing perennials like hostas, coneflowers, asters, and ornamental grasses usually benefit from periodic plant division. There are exceptions to every rule but these are good “rules of thumb.”
Now, before we continue with this topic: There are plenty of great websites about plant division, and I’ve included links to some at the end of this article. However, many of the illustrations look like a murder scene. There’s usually someone kneeling on the ground – with a knife in their hand – and plant parts scattered everywhere. I want to remind you that there are many gardening tasks that are appropriate for venting hostility, but plant division should not be one of them. In addition to traumatizing the plant, you don’t want to traumatize the neighbors when you’re outside. Well, not in the front yard anyway.
PLANT DIVISION – who, why, when, and how to
The main reasons for dividing perennials are to control the size of the plant, to rejuvenate them, and to increase their number. Dividing perennials is also an easy and inexpensive way to create additional plants for your garden – or to share. I’ve heard it said that “a gardener with no hostas has no friends.” Or enemies, depending on how you feel about hostas.
Perennials will let you know when they’d like to be divided: flowering is reduced with the flowers getting smaller, or a plant may lose vigor. Perhaps the growth in the center of the plant dies out, leaving a bare spot with a circle of growth around the edges, or the plant simply has outgrown its space.
In general, it is best to divide a plant when it is not actively flowering, since this draws energy away from establishing new roots and emerging foliage. In Ohio, the date to divide your plants depends on when they emerge and begin to grow, usually a month-long window of time between March and May. Pick a cool, cloudy day if possible.
For example: Hosta “eyes” often emerge around the beginning of April in Ohio (in a normal year, not the winter of 2017). Yes, hostas have “eyes” and they are watching you every minute, so proceed carefully. Most folks think you start by digging out the clump of hostas but NO. First you dig the hole where the hostas are going to end up (or you call your friends who want divisions). Anytime you move a plant, you want to minimize the stress of having the roots out of the ground. Prep the destination hole with lots of compost in the backfill. NOW dig up the entire clump of hostas. The roots will likely hold the clump together very tightly. Set it on the ground and use a knife, shovel, or sometimes an axe, to divide the plant into new, smaller hosta clumps. Try not to spew plant parts everywhere like a scene out of the movie “Psycho.” Replant the new divisions, each containing 3-12 “eyes” in their new homes, backfill and water thoroughly. Now collect your tools and baaack away carefully!
Most perennials are easily divided every few years. It’s a fun and economical way to fill in your yard. From a design POV, repeating plants brings rhythm and unity to a landscape. Win-Win-Win! Just remember that propagation should be an enjoyable activity – not an act of plant punishment.