Wait to divide these spring-flowering perennial plants until fall.
Bob Stefko
Whendividing perennials, most plants do well when divided in spring.
Others, particularly semi-woody perennials, don’t take well to dividing at all.
Credit:Bob Stefko
It may take the divided plant weeks or months to recover.
Dividing perennialsafterblooming allows the plant to focus all its energy on getting reestablished.
The lists below are not exhaustive, but they include several popular and commonly grown perennials.
Credit: Karla Conrad
For northern locations, that means dividing should be done in late August or September.
For gardeners farther south, it can be as late as the end of October.
Plants to Never Divide
There are some plants you shouldnt divide regardless of the season.
Credit:Kindra Clineff
Woody perennial shrubs, such as roses and some herbs, fall into this category.
Most plants with taproots also dont take well to dividing.
If you’ve got tree peonies, these are on the never divide list.
Credit:Kritsada Panichgul
Oriental poppies should be divided every 4-5 years.
Siberian Iris
Kritsada Panichgul
Siberian irises (Iris sibirica) grow in a large clump.
Eventually, they become crowded, and flowering decreases, which signifies it’s time to divide.
Credit: Bob Stefko
Divide Siberian irises in late summer or fall.
Late summer is the best time.
Allium
Also calledornamental onions, alliumsgrow from bulbs that multiply each year.
Credit: Bryan E. McCay
New transplants may take a year to recover from division and resume full flowering.
Jack-in-the-Pulpit
Divide spring-bloomingJack-in-the-pulpitplants (Arisaema triphyllum)after they’ve entered dormancy in autumn.
Wear gloves because the sap can be a skin irritant.
Credit:Matthew Benson
Break off any offsets that have formed by hand and replant.
Lift the entire plant in late summer or fall when flowering has finished.
Separate clumps by teasing them apart; don’t hack it with a tool.
Credit:Bob Stefko
Prairie Smoke
A gorgeous wildflower, prairie smoke(Geum triflorum)forms large clumps.
Wait until the plant has finished flowering and setting seeds.
When the seed heads are drying is a good time for division.
Credit:Denny Schrock
Lily
True lilies, plants from the genusLilium,are planted or divided in the fall.
This group includes Asiatic, Oriental, and trumpet lilies, but notdaylilies.
Dig as deeply as it’s possible for you to and lift the clump.
Credit:Denny Schrock
Look for natural divisions where the bulbs seem ready to pull apart by hand.
The stress factor for the plants in frost-free climates is heat, not cold.
Wait until the temperatures get colder in the fall and divide your perennials in late November or early December.
A hand trowel works just fine for smaller plants.
For larger perennials, the extra leverage of a garden fork makes digging and lifting easier.
Wear sturdy gardening gloves because injuries can happen when hacking apart a heavy bunch of roots.
