The question of how to divide perennials is asked a lot, so here are my best tips on the issue!
Fall is a great time to dig and split those spring and summer perennials. A long, cool fall with plenty of rain will help transplanted roots get established before the plants go dormant for the winter. In our northern areas, divide perennials 6-8 weeks before the ground typically freezes.
Three of the many reasons for dividing perennials are:
- To control the plants size
- To rejuvenate an older plant
- To increase the number of plants in your garden and to share with others
As I said, fall is the ideal time to divide the summer bloomers. By dividing them when they aren’t flowering, allows all the plant’s energy to go into the root and leaf growth for the last remaining months of the season.
Most perennials should be divided every 3-5 years. Some perennials such as chrysanthemums and asters may need to be divided every year or two or they will overcrowd themselves and not bloom at all. Bleeding heart and peonies may never need to be divided unless only to increase how many you have in your garden. My bleeding hearts divide nicely and grow quite vigorously even when dropped inadvertently along the garden path! As with many things, preparation is 9/10th of a good job. So prepare ahead of time when you plan to start the dividing process.
First: if your soil is dry, water the plant and the surrounding area thoroughly a day or so ahead of time.
Second: prepare the bed area where you plan to place your transplants.
Third: trim the stems and foliage to 6 inches from the ground for ease of handling.
Once you are ready to dig, use a sharp spade or garden pitch fork to dig down on all 4 sides of the plant. Start your dig about 4-6 inches away from the plant or about where the plant drip line would be. Pry underneath the plant with your tool and lift the entire root ball clump out.
For really big plants, you may need to cut the root ball into smaller pieces for easier handling. Next, shake or hose off loose soil and remove dead leaves and stems. Now you can see what you are doing better. For perennials with “tangly” spreading type of roots (aster, bee balm, purple cone flower, lamb’s ear), you can usually pull the roots apart by hand or cut apart with scissors or a knife. Large plants with these “gnarly” roots may need forceful separation with two spades pushing in opposite directions to separate them. Divide the plants into clumps of 3-5 sturdy shoots. Be sure to NOT let the roots dry out. Keep a pail of water nearby during the process. Plant your divisions as soon as possible either in the ground or in pots. I always amend my soil with a little compost equal to what came out during the transplanting process.
Be sure to replant the divisions to the same depth as they were when in the ground originally. Firm down the soil and water well. Mulching is recommended as the new little transplants head into winter. I use pine needles because I have an over abundance of them in my yard, but leaves and grass work as well.
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