Dividing Perennials

With warm days, cooler nights and more rain in the forecast, September is a great time to divide spring and summer flowering perennials.

Dividing perennial plants is a great way to share perennials, make a plant smaller that has grown too big for its space, increase the stock of a favourite plant, or the plant has become woody in the centre.  Division of these plants encourages vigorous new growth.

The rule of thumb is that spring and summer flowering perennials should be divided in the fall after their blooms are finished.  Perennials such as hosta, Shasta daisy, Leopard’s Bane are best divided in the fall.  Any perennials that have their flowering show in the late summer and fall are best left to the spring to divide, such as sedum.

Many perennials benefit from dividing every 4-5 years, although some plants such as lamb’s ears, bellflowers and yarrow should be divided more frequently (every 2-3 years).  Some plants (peonies) don’t need to be divided at all.

This is a great time to divide your spring and summer flowering perennials as their flowering stage is finished and the plants can put their energy into developing their root systems and leaf growth.  Be sure to watch the weather when dividing.  Cloudy days are great, even a fine drizzle is ok, but avoid the sunny and hot days as this puts too much stress on the plants.

  • Cut back the leaves to 2” from the crown to lessen the amount of moisture loss
  • Having the new planting hole prepared before you dig will limit the plant’s time out of the ground and the stress on the root system
  • It’s easier to divide a perennial by first digging and lifting the entire plant
  • Use a sharp shovel or flat edged spade and slice completely around the outer perimeter of the plant a few inches away from the foliage (dig out as much of the root ball as possible)
  • Once the perennial is dug out, pull apart the plant or use a sharp shovel (make sure that each section has growing tips and roots)
  • Re-plant the sections using Dufferin Garden Centre recommended planting instructions.
  • Be sure to use Bone Meal and water in well