By Kris Winkler
Master Gardener
We all love our perennials and then they start to spread and take over our flower beds. I love waves of color, but there are times when I must divide. I usually divide in the Spring, as the plants emerge and there is good moisture, but you certainly can and should divide some plants in the Fall. Here are some guidelines that I follow:
● Perennials are plants that grow back each year.
● Dividing or splitting a single perennial into multiple plants helps the plant perform better.
● When perennials are divided, there is more space for roots to grow and absorb nutrients and water.
● Dividing perennials can help manage the size of the plant.
● You will have more plants of the same kind to add to your garden when you divide a perennial.
Divide fall blooming perennials in the spring because
● New growth is emerging and it is easier to see what you are doing
● Smaller leaves and shoots will not suffer as much damage as full-grown leaves and stems.
● Plants have stored up energy in their roots that will aid in their recovery.
● Rain showers that generally come along with the early season are helpful.
● Plants divided in spring have the entire growing season to recover before winter.
Divide spring and summer blooming perennials in the fall because
● There is less gardening work to do in the fall compared with spring.
● It is easy to locate the plants that need dividing
● Perennials with fleshy roots such as peonies, Oriental poppy, and Siberian iris are best divided in the fall.
● When dividing plants in the fall, time it for four to six weeks before the ground freezes for the plants roots to become established. This is particularly important in our cold, Wisconsin climate.
Dividing perennial plants on a regular basis has a whole slew of advantages for both the gardener and their plants. For starters, it’s an excellent way to keep plants healthy and manageable over time. Perennials that remain in the soil for too many years begin to experience issues. As their roots become overcrowded, it becomes difficult to absorb the nutrients and moisture plants need from the soil. When this happens, not only do plants struggle to grow, their blooming cycles diminish, or in some cases, stop all together.
But dividing your perennials ever few years solves this issue. And beyond keeping root structures healthy and blooms strong, it also creates a slew of additional plants — all for free! Not only will it help to keep weeds out naturally with a thick coat of foliage, it also means less mulch and mulching chores too! I use way less mulch as my plants spread and have hardly any weeding. Some hints for a good experience dividing are:
#1 Select Healthy, Mature Plants
The best way to create a strong new start from a perennial plant is dividing from a healthy, mature plant. Select larger plants with good foliage and strong growth habits.
#2 Work When The Soil Is Dry
Don’t attempt to transplant after heavy rains or watering. Allow the soil to dry out a bit before digging up plants.
#3 Dig Outside Of The Root Zone
When digging out plants, always remove as much of the root mass as possible. The roots of a perennial plant are its lifeline, and the more you remove, the better chance of survival for new divisions. Use a sharp shovel to dig an inch or two out from the edge of the root zone. For most perennials, their root zone will be equal to the outer most edge of the foliage.
#4 Divide Perennials From The Bottom
Instead of trying to split perennial plants from the top down, split from the roots through the plant. Once your perennial has been lifted from the ground, turn it over so the foliage is face down. Next, using a sharp shovel or knife, divide by cutting down through the roots.
By flipping the plant over, it reveals the entire root structure, allowing you to split the plant in even sections. By cutting the roots in like-size sections, new plants will grow to about the same size as they mature. This is great for keeping flowerbeds looking uniform and well-groomed.
#5 Transplant Quickly
Here is a big hint: don’t keep transplants lying around for days to plant. The quicker a divided perennial is planted, the better chance it has to settle in and establish a few roots before winter. Transplant to a new location as soon as you dig and divide, being careful not to let the roots dry out completely.
#6 Build Nutrients Into Your Planting Holes With Compost
When transplanting, always add compost into the new planting hole along with the soil in the beds. Compost is not only full of nutrients, it also helps retain moisture around the roots of plants.
And don’t worry if the new transplants foliage drops off or dies back in the fall. Most are completely finished growing by fall up top, and they are simply heading into dormancy. But by getting these plants split and in the ground in the fall, it allows the roots to be ready to grow strong the following spring.
# 7 Creating A Holding Bed
So what if you don’t have a place for your new plants just yet? Then create a holding bed! You can use a small corner of your property, or an unused space in your vegetable garden to hold plants now until you need them next year. Holding beds are a great way to establish and keep new plants over winter. We have used them for years to grow hundreds of starts until we need them for new beds or a different look in the landscape. Then in the spring you can replant in your yard or give away to friends or sell at the annual Master Gardener sale.
Go to the https://extension.umn.edu/planting-and-growing-guides/dividing-perennials to see a great chart on when you should divide your perennials.
