Off the Fairway

Division in the Garden

Plant divide. Photo provided by Finegardening.com.

Something that took me years of experience to learn is that there is a natural lifespan for some plants. Obviously providing all the necessities for the healthiest life possible will increase the longevity and performance, but regardless of providing perfect locations, quality soils, optimum nutrition, and the right amount of water, there still comes a time when plants start to show their age and sometimes it’s unexpectedly sooner than we may have thought.

As I write this article, there is so much talk of division amongst Canadians. The negative use of the word inspired me to write about plant division, hoping to give everyone a more positive use for the word.

Plants have a lifespan, some longer than others, and some show signs of aging even in perfect scenarios. When it comes to plants, we have two main types for simplicity’s sake for this topic. We have woody shrubs, which range in size and perennials which includes ornamental grasses. Woody shrubs typically have a longer natural lifespan than perennials and show their age as they get older by slowed or reduced flower production, branch die back or rot, increased sucker growth from base or from higher up on older branches, and what’s called haloing. Haloing is seen more often in shorter shrubs, 3’ in height or less. Haloing is when there appears to be no growth coming from the center of the plant, so you have a ring of growth coming from the outer portion of the crown of the plant and a circular bare appearance within the center of the shrub, hence it being called a halo. If the above-mentioned symptoms of old age are left unchecked or have been left unchecked for a long period, then it’ll be time to consider replacement. However, it is possible to rejuvenate or prolong the lifespan when the signs of age start to show up. For your larger woody shrubs, pruning out older growth to allow younger growth to take its place will increase longevity. In some cases, a full shear back by 1/3 is required, and prune overgrown suckers from the base. I should add that pruning techniques are specific to the Shrub, so know what you’re working with before hacking at it.

When it comes to Perennials, the halo is a sure sign that it has gotten old and may not be long for this world; ornamental grasses are especially notorious for this after a few years. However, there is a way to bring these tired, worn-out plants back to life. This task is called DIVIDING, also known as splitting. This can be done successfully to shrub species as well. Dividing is digging the plant up, using a sharp edger, spade, knife, or hand saw and splitting the plant into 2 or 4 pieces and replanting them separately. This removes the halo effect, causes the plant to produce new, younger roots and gives you a couple additional plants to work with, discard, or even use the division to give as a gift to a friend for their garden. As I said, ornamental grasses are bad for the halo effect, Astilbe seem to get old fast and require splitting every couple of years. Once Hostas get older, they slow their flowering and start to thin out in the centre, something that also happens with Black Eyed Susan’s, Echinacea, and Iris, to name a few. Some shrub species that start to halo as they get old are Hydrangea Arborescens, Hydrangea Macrophylla and Spirea species. Shrubs are a little more labour intensive to divide but can be done.

Some perennials are long lived and don’t require much rejuvenation techniques at all. There are some who, over time, push themselves out of the soil or their crown raises which makes them weak and susceptible to crown damage. When you see this happening, dig it up and replant back at a proper depth with the crown flush with the soil level. Be kind, stay healthy, and get in your gardens at the earliest possibility. ■

Ornamental grass with a halo. Photo provided by Chris Cumming.

Chris Cumming CLP, Horticulturist Cell: 705-644-3994 chriscumming@live.ca