Time Required: Under 2 hours
Dividing perennials is a great way to turn one plant into several free plants that can be used elsewhere in your landscape. The best time to divide most spring- and early-summer flowering perennials is in the fall. The best time for most late-summer and fall-flowering perennials is in the spring. This guide will teach you how to divide up your perennials and add them to your landscape.
Most perennials will need dividing at some point, typically every two to three years to avoid plants competing for nutrients and water. Dividing perennials is necessary to avoid overcrowding and to keep your plants as healthy and lush as possible. Plus, it helps you get two plants for the price of one! Grow a beautiful garden on just half the budget when you divide perennials.
Some perennials, such as Sedum 'Autumn Joy' and Siberian irises, need frequent dividing to perform their best. Others, such as peonies, can go decades without needing any division. You can tell when a plant needs division if it develops a dead core in the center of its crown. Also, if the foliage is fairly lush but the plant is producing steadily fewer flowers each year, it may need dividing.
Unsure which perennials need dividing? Here are some tips:
- It's time to divide when you see overcrowding, a clump with an empty spot in the middle or outward falling stems.
- The best time to divide perennials is in the fall - divide and transplant at least six weeks before the first hard freeze. Avoid moving fall-blooming perennials while they are still in flower. Mark and save these for spring.
- The day before, water your plants and cut foliage by a third.
- The best time to divide and conquer is on a cloudy day. Plants recover more quickly if the sun isn’t beating down on them.
- If the weather becomes hot, shade your perennials with a row cover until they are established since dividing perennials stresses the plant.
- Replant new divisions as soon as possible. Plants can sit for a few days out of direct sun without being planted, but the longer they are out of the soil, the less chance they have of settling back into your landscape, or someone else’s.
- For smaller plants, lift the root ball entirely from the soil.
- For larger plants where lifting the root ball would be difficult, remove a portion at a time by slicing through the root ball with a spade and then digging up that portion.
- Leave one portion of the original plant where it is.
- Break the root ball into smaller sections with your hands when working with delicate plants.
- Larger, more tightly knit root balls will require slicing into sections with a knife.
- Very large, dense root balls, such as those of daylilies or Siberian irises, will require prying apart with two spading forks. You may even need to use a small hand ax to hack through difficult root balls, but this should be a last resort since it is very damaging.
- If your perennial has a rhizome or tuber that grows horizontally, like bearded iris, dig it up and use a sharp knife or pruning shears to cut it into pieces. Leave at least one bud and some roots on each piece.
Tip: If you break off roots, don’t worry. Just make sure each division has some roots attached.
- Most perennials can be divided into several smaller plants. Replant these sections as desired or give away to friends.
- When replanting in the original spot or filling in where just a portion of the root ball was removed, work in a shovelful or two of compost to improve the soil.
- Replant the divisions at the same depth they were growing.
- Water new plantings well.