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Divide and Conquer

Dividing Perennials in Fall

HI! I’m Norah, the horticulturist at Alternative Choice Gardening Centre. I’ll be blogging mostly on my specialty: trees, shrubs and perennials. I have a specialty in landscape design, have been certified as an arborist and love talking gardens!

As I write this in early October, the weather in Manitoba is fantastic. We’re looking at a week of lovely, moderate day time temperatures and crisp nights. This is the perfect time to divide your perennials. Who wouldn’t want free plants? It is also very important for the health of your perennials to divide them every three to five years. Are your perennials not performing well, are they maybe getting bare in the middle with just a ring of foliage (Iris come to mind)? It’s time to divide.

Now, we’re talking herbaceous perennials here, things that die right back to the ground each year like peonies, daisies, cone flower and such. You cannot divide woody shrubs or trees, it just doesn’t work. I love fall dividing, transplanting and planting. First, you can still find the plants, you are not waiting for them to come up in the spring. Second, they are already going to sleep and will hardly notice that they’ve been moved. Most plants operate on daylight hours as well as temperature, so our hardy plants know that hibernation is coming and they have nothing to do but root.

You’ll need a shovel or spade, maybe a garden fork on big old clumps, I like a tarp to move the clump on to so you are not dirtying up mulch. I’d always love to see them replanted with bone meal in the hole, , as it provides the nutrients to make strong roots. A root stimulant like Myke Tree and Shrub is also fantastic. It’s an excellent time to improve your soil with natural fertilizer like compost or manures, our gardening and installation crews use Sea Soil with almost every planting. Peat Moss only if you have very sandy soil.

Here is an example of a daylily that would be a prime candidate for dividing. Photo by Keywest Photo

You should decide where your new plants or going and perhaps have the hole ready. Now, let’s take a moment here to talk about single perennials versus a ‘drift’. Many customers bring me photos of lush gardens with large swathes of single perennials; they want that look but have planted a single plant. In the picture, the perennials are often planted in groups of three to five plants. Most perennials will get about a foot wide, maximum, so to get that grouping that’s three or four feet wide, you need to plant multiples. So if you want a large clump, just plant your divisions around the same area.

So, starting about eight inches from the base of the plant, dig all around the plant. If you’re working in a bed with landscape fabric and mulch of wood or rock, move the mulch off to the side, using a box cutter cut an ‘x’ in the fabric and roll back the four corners. You may need to remove a bit of soil from the garden to get to the roots at the bottom of the plant. Very few perennials have a tap root, most of the roots will be in the top foot. You do not need to get uptight about preserving all the roots: the plant will generate more quite easily. Now, you may have to use a garden fork to get under the plant and pry up a bit, or you may be able to leverage it out with your spade. Once it’s popped out get it on your tarp, if you’re using one. Find the centre of the plant, maybe moving aside the foliage to find a nice line and push your shovel down that line from top to bottom. Really!!! It’s that easy!!! You don’t really have to be gentle or delicate, just whack it in half. Sometimes, if the plant is mature and healthy, you could make three or four divisions, just as long as you can get a decent amount of root with each piece. Replant your pieces as soon as you can, keeping the soil level in the new hole at the same place as the soil level was on the plant. I, personally, would prefer you not cut the foliage because the plant is suffering enough stress.

Replant your pieces as soon as you can, keeping the soil level in the new hole at the same place as the soil level was on the plant. Add in your amendments and mix well with your native soil. I, personally, would prefer you not cut the foliage because the plant is suffering enough stress.Then, water, water, water!Most perennials you dig up will have stringy to fleshy to fibrous roots; some, like Iris, have a rhizome or thick, knobby, potato-like thing. Same rules apply: just get a decent amount of fibrous root with each chunk. With Iris, it is extremely important to have the same soil level on the plant in the new planting: they like a bit of rhizome exposed.

So…easy, right? Now, off you go and divide and conquer!


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