5 practical pointers for dividing perennials

With most perennials, you can increase your supply of plants by digging, dividing and replanting the best specimens. But do you know when and how? Here are five pointers for dividing perennials that really work.

[Image credit: iStock.com/Westersoe]

Most perennials need to be divided every few years to remain vigorous. When you dig and divide perennials depends mostly on when they bloom. To go about this garden task:

• Divide perennials that flower in mid- or late summer, such as asters, chrysanthemums, sunflowers and Japanese anemones, in spring.
• Divide spring and summer bloomers in late summer or fall so that they will have time to develop new roots before winter comes.

Some perennials prefer to be divided very seldom, if at all.

• Peonies, for example, would just as soon be left alone for 10 years or more before you consider dividing them.

When dividing perennials, you don't have to lift the entire clump.

• To separate one or two growing crowns for replanting, gently loosen stems and roots on one side.
• Next, cut the small plants off cleanly with a butcher's knife, another type of sharp knife or a small spade. Be sure to retain growing points or buds, as well as roots, on each piece.
• Finally, replace the soil around the remaining roots and plant the little division right away.

There are ways to divide certain plants that will save you from a lot of unnecessary effort.

• To divide an entire clump, use a digging fork to loosen the soil around the clump, then lift it from beneath. A small shovel also works, but requires much more effort.
• Fine-rooted plants, such as dianthus and bee balm, can then be divided by simply pulling them apart with your hands.
• Use a sharp knife or spade to separate any plants with tougher roots by cutting them into smaller clumps.

With older plants, or ones you haven't touched in a while, you'll need to divide them in a way that doesn't save all of the plant itself.

• Divide older plants that have become woody by digging the clump and saving only the young plants growing near the outside edge.
• Dispose of the parent plant once you've saved its healthier offspring. The older portions of the parent plant tend not to be very productive.

If you have no place to put all of your divided perennials, set some in pots. They'll still thrive, provided you give them all the necessities: sunlight, water and fertilizer, when needed.

• Perennials in containers will make themselves at home until you find a place for them, which may be in a friend's or neighbour's garden.

Perennials tend to be hardy plants that are, for the most part, relatively care-free. And when they become too big for the garden, they're easy to divide and replant elsewhere, or give away as gifts.