Dividing is multiplying

by Susie Cosack, Master Gardener

Dividing perennials is an easy way to have beautiful blooms year after year while at the same time creating more plants for your garden.

It is a task I do every two to three years, or when my plants have outgrown their given space and need more room. The entire plant is weakened by having a large number of roots and leaves competing for water, food and light. Division of these overgrown, leggy plants is actually very good for them and essential for many perennials to stay vibrant and healthy. It is also a great way to spread plants around the garden, allowing me to create symmetry, repetition with colours and patterns, as well as change designs or placements that just don’t look right.

Dividing means to dig up overgrown plants and split them into smaller pieces to replant. The same traits, colours and characteristics of the original plant will exist in in each divided section. I generally divide spring and summer blooming plants in the fall, and fall blooming plants in the spring.

There are always some plants, such as sedum or hostas, that are exceptions to the rule. With the proper care they can be divided anytime during the growing season.

I usually wait to divide my perennials until the frost is out of the ground early in the season or four to six weeks before a killing frost in the fall. Having tender roots, plants need time to regrow and should not be subjected to harsh wavering temperatures during this process.

When dividing, I dig out the entire plant I want to split, including as many roots as possible. I carefully separate the plant into sections. An ideal size is about one-quarter of the original plant, each one having stems and roots.

Since there are many different root types, using the right tool to separate is important. Plants with clumping root systems like Hostas need a sharp clean spade or hatchet. Thin rhizomes or stolons (runners) like bee balm has, can be divided with clean sharp knives, pruners, spades, or garden forks. Tightly woody crowned plants like my peonies divide with a clean sharp handsaw or spade. And finally, when dividing thick rhizomed bearded iris I will again use clean sharp knives or pruners. Generally, think carefully before you cut, and use the tool that works the easiest for you.

I always know in advance where the sections will be replanted. I do this as soon as possible in a hole dug twice as wide as the roots and a little deeper than they are long. I make sure the plants are reset at the same depth they were growing in before being dug out. Sometimes I pot them as gifts, or make donations to local plant sales. I water all the divisions well to let the soil fill in around the roots and reduce any air bubbles. I top up with more soil if needed. To the plant, dividing is stressful so I give them extra attention in the coming days. Once the roots establish they will grow again. When the work is done, my one plant has been divided into many. Dividing is multiplying.

Consider this: dividing your perennials will reward you with healthier plants and provide you with plants to share with friends or to expand your own garden.