Perennials are wonderful garden plants. Plants that are hardy enough to continue growing each year in your garden are considered perennials (as opposed to annuals which you need to replant every year). They can be very low maintenance once established, providing gorgeous blooms and even edible parts through the growing season.
Dividing perennials is often the only job that is needed to keep them in tip-top shape. Dividing helps perennials from becoming overcrowded, keeps them within the space designated in the garden, and can give you more plants for free!
As perennials develop an established root system in the ground, they spread and form larger and larger clumps. Dividing helps to improve aesthetics and blooming as well as protection from fungal diseases and insects. If any of your perennials are underperforming, dividing may just be the solution!
When to Divide Perennials
The best time to divide perennials is after they have bloomed and gone dormant for the year. With the exception of irises and fall bloomers most perennials would adore to be divided in the fall, and thank you for it next year. (Divide irises in summer after blooming, divide fall perennials in fall after blooming or the following spring). Dividing perennials in the fall gives the plants more of a time for the roots to develop strongly into the soil before the next gardening season.
Divide the perennials when the plants are looking full and lush but before they start to show signs of overcrowding. The growth and performance of perennials decreases as the plants become crowded. The centers can start to die or the whole plant can underperform like this Heuchera.
Of course, do what you can and divide the perennials when you have the opportunity, but if you’re noticing that your plant is performing well but is starting to push the boundaries of the space, this is the time to divide the plant. You can use divisions elsewhere in the garden or to give them to friends. Free plants!
How to Divide Perennials
If you’re dividing in the fall, it shouldn’t be too difficult to find a cool day. The best time to divide is when the weather is not overly warm as plants establish more quickly in the soil when they aren’t under stress.
Lift the plant from the soil with as little root disruption as possible. Imagine that the roots below equal the size of the plant above to get an understanding for how much spread there is. Use a shovel to start digging around the soil at the edge of where you think the roots are. Dig the perimeter of the roots by driving the spade around the root ball. Now put the spade into the soil and gently trying to start to lift the plant from the bottom of the roots by pushing the handle down and the spade head up. Do this around the circle until the perennial pops out of the soil easily.
I find it handy to have a large tarp or blanket in order to put the big perennial roots on so I can then take a good look at what is there. Shake off the soil have a look at the roots. How much are they entangled? Are there any plants that look like they’ll easily start to separate? Use your hands or two garden forks to gently pry the roots of the divisions of plants apart. If the roots are strongly tangled into clumps difficult to pry apart you can use a garden saw (keeping in mind that this might cause damage to the plant).
Prepare your garden soil for transplanting by adding in compost and manure into the soil. Remove any debris or diseased leaves and give the soil a good turning so that it continues to be healthy, light, and well draining.
Plant a vigorous, healthy-looking section of plant back into the space that you removed the larger clump from. Backfill the area with soil and water well.
The remaining sections can either be planted in the garden right away or potted up to be given away. The same rules apply whether the plants are being transplanted to other areas are put into pots that they should go into healthy soil rich with compost and watered well.
If any parts of the plants don’t look healthy then dispose of them rather than planting them in the ground or in pots. There should be plenty left over of healthy plants and you want to start them off on the right foot.