Many perennial plants grow in an ever widening clump. After several seasons of growing, these perennial plants will begin to die out in the centre and look more like a ring than a clump. When to divide perennials depends on the type of plant and how quickly it’s growing. You don’t have to wait until your perennial plants begin looking like doughnuts. In fact, it’s better if you don’t.
Keep an eye out for clumps that have grown 2-3 times their size within 2-5 years. Any over grown clump or any clump that has simply exceeded the space allotted is a candidate for division.
Spring is usually the best time for division, since the plants are actively growing their leaves are not so developed that the root system can’t take a little disturbance and still feed the top of the plant. However, just as different plants can go different lengths of time before being divided, some plants, like peonies, prefer to be divided in the early autumn.
Marty DeHart demonstrates how to divide perennials in early Spring.
However your divide your perennial plants, you should treat them like new seedlings.
- Try and do your dividing on an overcast day or at least not in during the hottest part of the day.
- Don’t leave the exposed root ball sitting about any longer than necessary. Hot sun and breezes will quickly dry the roots.
- Keep them well watered until new growth appears.
- Provide some shade if they appear to be wilting during the afternoon. A floating row cover will protect them from the hot sun.
Perennial plant division is intimidating when you first think about tearing apart your precious plants, but the more you do it, the better you will get at it and the better your perennial plants will grow.