Dividing perennials — digging up the plant and splitting it into multiple plants — allows the roots more space to grow and improves overall plant health. In the fall, the soil is still warm enough to allow root growth before winter, and plants are shifting energy into roots instead of foliage or flowers.
If you notice your plants are producing fewer blooms or growing outward with an empty center, then it’s time to divide your perennials, according to Homegrown NH Host Emma Erler, lead horticulturist at Kirkwood Gardens.
Fall weather is typically cool and wet, which helps reduce plant water loss and stress after being transplanted.
If you are dividing in the fall, Erler recommends doing so by early October so plants have time for their roots to establish before the ground freezes.
Erler notes that many gardening guides suggest dividing spring-flowering perennials in the fall and fall-flowering perennials in the spring. Some perennials do respond better to being divided at a certain time of year, in practice, but generally they can be divided anytime – depending on when you have time and a shovel in hand.
You can divide perennials in summer, Erler says, but it takes longer for them to become established, and their blooms may be reduced for a longer period while they recover.
How to divide
- Dividing perennials is easiest when the soil is damp. Wait for rain or water beforehand.
- Dig up entire the perennial clump with a shovel, spade or fork. Try to keep the root ball intact by digging 8-12 inches away from the crown, going all the way around the plant and lifting the perennial from the soil.
- Break the plant into smaller sections by cutting the crown with a shape spade or knife and gently pulling the roots apart with your hands.
- All divisions should have a minimum of three shoots to be successful and to bloom again quickly.
- Plant divisions as soon as possible. Add compost to the area around the dividing plant. Compost is a slow-release soil amendment that improves structure and feeds soil without forcing tender new shoots. Wait to fertilize until the following season.
- Water immediately after planting and continue for the remainder of the growing season.
See you in the garden!
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Homegrown New Hampshire is a collaboration between Squam Lakes Natural Science Center and NHPR.
