And then there were 2… or 3… or 4…
A while ago I promised a blog about dividing perennials. While it’s taken me some time to put virtual-pen to cyber-paper, it is still a relevant topic this late in the season.
Let’s not waste any more time and get straight into it!
Throughout this growing season, did you notice any perennials completely outgrowing their allotted garden space? Did you notice a perennial that grew as a ring with a big empty space in the middle of it (see photo)? Did you have a perennial that under-performed in it’s floral display? These are all signs that your perennial in question needs to be divided (and probably should have been divided years ago)!
Perennials are NOT meant to look like donuts! This grass is in need of some dividing.
Dividing is a way to rejuvenate our perennials. Clumps can get overcrowded and experience a reduction in vigour over time. Additionally, some perennials simply begin to take up too much space in our gardens- becoming bullies to our other plants; in this case, dividing is a way to keep the size of a perennial patch in check.
Dividing is insanely easy. Plus it is a great [free] way to increase the number of plants that are available to you*. While, you may not want the same Hosta covering every square inch of your garden, having divisions at your curbside in a box labelled ‘free plants’ makes you a popular person in your neighbourhood, not to mention you gain some serious ‘garden-related street cred’ when people see that you have the nerve to rip plants from the ground only to slice ‘em up and give them away. (“Wow” people whisper in awe, “That person must really know what they are doing in the garden…”)
TIMING
Dividing is typically done in the spring and the fall when temperatures are cooler and moisture is more abundant. Blazing heat, intense sun, and drought are all plant stressors that are minimized in the spring and fall months. The process of dividing is stressful enough as it is- why unnecessarily add environmental stressors into the mix?
As for spring versus fall, common advice states that fall flowering plants are to be divided in the spring and spring-flowering plants are to be divided in the fall.
Why all the rules?
First of all, it should be known that if you divide a plant too close to it’s flowering time, it may not bloom- it is too busy getting it’s ‘smaller self’ reestablished! If divided and cared for properly, you won’t kill the plant, but sacrificing blooms is a real possibility (but not a guarantee). If you divide while a plant is in flower, not all the plant’s energy will be put towards growing new roots, so reestablishment in the garden can take longer.
Another consideration with respect to timing is the length of time available for the plant to reestablish itself. Plants divided in the spring have a whole growing season to set new roots and bounce back from the ‘operation’ whereas plants divided in the autumn months have a much smaller window of time to settle into their new size and surroundings before the snow flies. This can be a problem for more tender perennials, but for the ‘tough-as-nails’ ones such as Hemerocallis spp. (daylilies) or Hosta spp… they laugh in the face of autumn division.
‘Tough-as-nails’ Hemerocallis spp. in bloom.
Since 90% of the plants that I divide are these super-strength perennials, I typically divide them in the fall (and sometimes quite late in the fall)… they always bounce back beautifully; besides, the spring is busy enough as it is!
One final note with respect to timing: I typically time my dividing for when the soil has some moisture in it but is not saturated. Trampling on a wet garden bed is a great way to compact the soil which is bad for root growth and therefore the health of the plants in the garden, so I avoid this at all costs.
HOW TO DIVIDE
Dividing a perennial can be completed in a series of simple steps. I will use a Hosta to illustrate the process; it is a great perennial to start with if you are tentative about this whole procedure!
Step 1: Select your candidate for division
Step 2: Dig all around the clump with a spade, starting close to the drip line of the plant (the point away from the plant to which the leaves extend) and moving inward when you get a sense of where the roots are. You will sever some of the roots in the process and that is fine, but your goal is to leave as much of the root system in tact as possible. Once you have sliced around the plant, it is time to get your spade under the clump to ‘pop’ it from the ground.
Step 3: Use a spade to slice the clump into multiple pieces. In this case I have sliced the original clump twice to magically turn 1 Hosta into 3 but I could easily have turned it into 5 or 6! Perennials can also be divided by hand or with a non-serrated sharp knife (suitable for perennials with finer, more delicate root systems), a handsaw (suitable for perennials with woody crowns), pitchforks or even an ax! Regardless of your tool, when you are ‘slicing and dicing’ be sure to cut out and discard the dead zones from the centre of your ‘donut plants’ as well as anything that looks diseased.
Step 4: Mix in a shovelful or two of compost or composted manure into the planting hole to amend the soil
Step 5: Plant a newly divided clump into the ground making sure the plant is put in the soil at the same depth that it was originally growing at and that the roots are spread out and away from the centre of the plant; cut down the leaves by at least half if dividing in the autumn
Step 6: Water around the clump to help settle the soil around the plant’s root system
Step 7: Exclaim “That was insanely easy! Now what am I going to do with the other two clumps…”
While there is MUCH more to say about division, this should help illustrate the basic technique. I will do more posts dedicated to dividing other types of perennials in the future, but in the meantime, have fun increasing the Hosta and Hemerocallis populations in your neighbourhood!
*It is important to keep in mind that dividing a plant is considered propagation. Some plants are patented and for these plants unlicensed propagation is prohibited (even for personal use).