I have received various tips from gardening friends on dividing and transplanting perennials. I decided to do my own research in order to give my transplanted perennials the best chance of survival in their new locations.
Perennials are plants that grow back each year. Perennials vary from one growing zone to another, so it is important to know the growing zone in which you are gardening.
Why is it important to divide perennials? When do you know it’s time to split them? Dividing perennials can help you manage plant size. We’ve all had the experience of plants getting too big and all of a sudden we have a jungle (currently, my prairie queen). This can choke out other plants.
When you divide a plant, the plant performs better and the roots have more room to grow and absorb nutrients and water. In addition, when plants are too crowded, airflow is restricted and plant disease rates are higher. Dividing is also a great way to add plants to your garden (or help out your local neighbor by sharing).
New growth and more (and larger) flowers are another result of dividing plants and keeping them at a manageable size. Dividing and moving plants around can give a whole new look to a garden!
Most plants really can be moved and transplanted at any time, but there is a best time to move perennials. The most important rule is to move the plants before they go dormant, so that the roots can establish themselves and the next season’s flowering is not affected.
Roots can continue to grow in cool weather until the ground freezes. Spring and summer flowering plants are best divided and transplanted in the fall. In the fall, it’s pretty easy to see which spring and summer flowering plants are overgrown and would be good candidates for division and transplanting.
Fall-flowering plants are best divided and transplanted in the spring. Basically, don’t divide and transplant when a plant is in bloom. Wait until this is done so that the plant’s energy can focus on regenerating root and leaf tissue.
The root system of some plants is more fleshy (tuberous) and it is better to transplant them in the fall, such as peonies, oriental poppies and Siberian irises. Other good choices for fall transplanting are astilbe, bleeding heart, bearded and Japanese iris, day lilies, lily of the valley, lilies and veronica.
Be sure to try to transplant your perennials about four to six weeks before the ground freezes to give the transplanted plants a chance to become established. I realize we live in northern Minnesota and trying to figure this moment out can be difficult.
Dividing perennials is really quite easy. It is best to try to do this on an overcast and cooler day. Sometimes in northern Minnesota, that’s easier said than done.
Dig up the original plant using a fork or shovel. Gently remove loose dirt around the roots. Separate the plant into smaller sections by gently parting the roots (into two or more plants) or by cutting the root balls into several sections with a sharp knife or gardening tool (like a spade).
Each division should have several healthy shoots and a certain number of roots. Keep plants moist and shaded until they can be transplanted; it’s even better if they can go straight to the new spot.
I’ve included a link below to the University of Minnesota’s Dividing Perennials spreadsheet. This is valuable information on when to divide, how often to divide, and other valuable information specific to 125 common Minnesota perennials. After reviewing this information, I now realize that I transplanted the forget-me-nots all wrong. We’ll see what happens in the spring.
• www.extension.umn.edu/planting-and-growingguides/ divide-perennials
• The University of Minnesota’s list of when best to divide and transplant perennials: www.docs. google.com/spreadsheets/ d/1Sv07afJ8jz9h_ CGA_ NNdjuFcaV83BUXt- T2uIsYUsNdI/ edit#gid=1250055917
Sally Koski is a University of Minnesota Extension Volunteer/St. Louis County Master Gardener who lives and gardens in Ely. Lawn and garden questions can be directed to Sally at [email protected]