Dividing Perennial Plants
What are the things we need to know?
When to Divide Perennials?
As a general rule of thumb, if it blooms in the spring, divide it in the fall.
If it blooms in the summer or fall, divide it in the spring.
This rule of thumb works pretty well for most plants although if you get any plant early enough in the spring, you can divide it easily then (including spring bloomers).
In the spring, dividing perennial plants is done as soon as frost is out of the ground. Even if it is cold out – too cold for you – it is fine to divide plants. They are still dormant, have made it through the winter and won’t even know they’ve been divided until they wake up and start growing. The warming soil will encourage them to make new growth.
Success rates tend to be higher for beginners with a spring division.
How to Divide Perennials?
There are several guidelines for dividing perennial plants. For the most part, when a plant requires division (or I want more of the plant) I put the shovel onto the root (hopefully between two growing points) and step on the shovel (shovel should point straight down)
If I’ve taken at least one quarter to one third of a two to three year old plant or a six-inch square chunk of an established plant, I generally have more than enough roots to establish another new plant. The trick is to ensure you have enough roots and a decent size chunk of the main rhizome or root structure so the plant contains growing points to send up shoots. If you can see the growing points (called “eyes”) as you can on some plants such as peonies, then simply ensure you get one or more of these eyes from mature plants to establish the young ones.
Dig and Divide Perennials?
Some writers would have you dig the entire perennial out of the ground and then chop it up. You then replant both parts.
This works although I confess I rarely do it because dividing perennial plants this way is too much work for me. I’m a lazy gardener and digging up an entire plant (only to replant half of the mother plant) strikes me as too much work.
The only time I’d do this is if the mother plant was small and I had to be very careful with the division.
Prying Apart Roots?
I know, there are some articles out there that suggest you use two garden forks back to back and pry apart the roots to get a good division. My only comment here is that these people have far too much time on their hands and have never divided plants on a commercial level.
This works if you want to spend the time and energy.
How Long Can I Leave the Roots Unplanted?
If you keep them cool, damp and out of the sun (cover with damp towel or old damp sheet) then they can stay out for several weeks if shaded.
But if you leave them exposed to the sun or wind, their lifespan can be measure in hours.
As long as I’m replanting my divisions within a few hours of digging them (and keep them fairly shaded while I’m working) I don’t worry about it.
Naturally, the faster you get them back into the ground, the better.
Do you have a question about Dividing Perennial Plants?