Why divide perennials?
Is it necessary? Is it right for my plants? These are great questions! There are several reasons to divide perennials:
- To create plants to gift to others
- To proliferate the plant
- To reduce the volume of a plant that has grown too dense or that produces less abundant flowers
- For relocation.
Division will not harm your perennials. On the contrary, if the plant has grown too dense, is taking up too much space or is producing fewer flowers, dividing it will give it some wiggle room and improve its flowering potential.
When to divide perennials?
It is preferable to divide perennials during the season opposite to their flowering season. Summer-flowering perennials should be divided in the fall, and fall-flowering perennials should be divided in the spring.
- Divide summer-flowering plants in the fall: astilbes, baptisia (false indigo), goatsbeard, dicentra (bleeding heart), gaillardia, geraniums, daylilies, heuchera (coral bells), hostas, poppies, peonies and Siberian iris.
- Divide fall-flowering plants in the spring: anemones, asters, chelone, chrysanthemum, black cohosh, echinacea, miscanthus (Chinese silver grass), fall sedum, rudbeckia, and goldenrod.
How often should perennials be divided?
There are no set rules! Nonetheless, some plants should be divided every year and others, every two or three years.
How to divide perennials?
Slice through the plant tuft cleanly and precisely. Use a sharp spade or even a hatchet for perennials with hard roots, and a gentler tool for more fragile plants.
The easiest method for dividing perennials is to cut the plants into pie wedges by sinking in the spade to remove sections while the plant is still in the earth.
Nonetheless, the standard method for plants with rhizomes (iris, peony, poppy…) and plants with fibrous roots is as follows:
Plants with rhizomes
- Cut back the foliage by one half.
- Use a spade to dig up the entire plant, keeping as many roots as possible.
- Use a knife to cut the rhizomes into several sections and keep at least one clump of leaves per section.
- Point the rhizomes in all directions so the plants continue to grow outward and inward.
- Lay the rhizomes flat and bury them just below the surface.
Plants with fibrous roots
- Use a spade to dig up the entire plant, removing a ball of earth with it.
- Use a sharp tool to divide the clump up into several sections.
- Plant the divided sections, taking care not to bury the collar.
Regardless of the method you use, fill the empty space with suitable soil such as Fafard’s 3/1 Annual and Perennial Planting Mix and add water.
Of course, there are exceptions! Ask your garden centre if you’re not sure!
Should perennials be fertilized during division?
Yes, it’s very important to fertilize during the perennial division process. Add natural transplanting fertilizer with bone meal to the bottom of the planting hole to help the plant better withstand the shock of division. Bone meal stimulates root growth for faster recovery.