Dividing Perennials: Keeping Fast-Growing Plants Under Control! – Pinetree Garden Seeds

Dividing perennials is a long-practiced gardening art form (or workout, depending on how you look at it), that is tedious but necessary. However pretty your perennials may be, they can also be growing, strangling machines that will overpower every neighboring plant around them without mercy. Many perennials grow very quickly, expanding into large clumps that can become unmanageable. If you don’t divide them consistently (typically every 2-4 years depending on the plant), the middles of the clumps can die out from being smothered by the rest of the monstrous plant. Overcrowded perennials can also suffocate themselves out of producing their signature blooms, so keeping them well spaced and divided will allow those big blooms to flourish. Dividing is also a great way to gift your friends, family and neighbors fresh adult plants!

Image from Dispatch.com

Okay, so when should I divide?

When your plant looks full, healthy and flourishing, dividing it may be the last thing on your mind… but it’s actually the best time to be thinking about it! Don’t wait for the plant to become huge and decrepit before dividing… at that point it’s already stressed, and you’ll be adding more stress on top by ripping it out of the ground and chopping it into pieces (as a highly graphic description). When your perennial clumps have grown 2-3 times their original size within 2-5 years, it’s time to divide. Also, any clump that is overgrown or starting to invade another plants space is a good candidate for division. Spring and fall are the best seasons to divide your perennials, as they’ll recover from the shock better in cool, moist conditions. If you decide to divide them in summer, be sure to keep them well watered. Be sure to replenish the soil you’ve pulled the perennials from with a healthy amount of organic matter. They’ll need the boost in nutrients in order to acclimate after being divided.

Alright, so how do I divide them?

The method is fairly simple, though it can be a little strenuous. You’ll be happier in the end for all your hard work.

1. First order of business is to dig the clump. To make things a little easier for yourself, water the perennial for a few days before digging it, which will the soften the soil for you. Insert your shovel deep into the soil around the perimeter of the plant to loosen the roots and isolate the clump.

2. Remove the clump. Force your shovel or garden fork underneath the root ball and seesaw the shovel up and down a few times to loosen the root system. Once you pull the clump up and out of the ground, give it a gentle shake to expose a bit of the root system, which will make it easier to divide the ball.

3. Separate the crowns and replant. Pry or cut apart into individual crowns (about five shoots per crown), each with their own set of leaves and roots. Replant the crowns as soon as possible to keep the root systems from drying out. Plant at the same depth as the original plant and water well. Cover the soil with a layer of mulch to conserve moisture.

What perennials should be divided when?

Perennials to divide every other year
Aster
Coreopsis
Campanula
Achillea

Perennials to divide every 3-4 years
Astilbe
Monarda
Rudbeckia
Daylily
Hosta
Phlox
Echinacea

DO NOT divide these perennials
Baptisia
Bleeding Heart
Butterfly Weed
Lavender
Oriental Poppy
Peony