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Spring Is a Great Time to Divide Perennials
submitted by Sarah Browning, UNL Extension Educator
Many perennial plants can be divided in spring, particularly those that bloom in fall or foliage plants like Hosta. Dividing plants during their non-bloom season, allows all their energy to go into root and foliage development resulting in faster re-establishment.
Division can reinvigorate older perennials by eliminating unproductive root sections and has the added benefit of creating new plants for your garden. There are no specific time lines for division of perennials. Many perennials benefit from division every 3-4 years, but some plants prefer division less often. Others do best if never divided or moved once they are in place, such as Dictamnus albus (Gas Plant). Signs that indicate your plants may need division include a decrease in flowering, spindly weak growth or a “dead spot” in the crown’s center with no foliage.
If a new garden location is being created, it should be prepared 2-4 weeks before planting by spading organic matter into the site and adding a handful of garden fertilizer to the soil.
Division can begin as soon as new growth shoots are 1-2 inches tall. Never divide plants on a hot, windy day; instead wait for a cool, cloudy day ideally with several days of light rain in the forecast. This will prevent rapid water loss from plants that have lost a significant portion of their root system. In preparation for dividing, water plants thoroughly a day or two beforehand. This ensures plants are fully hydrated before digging and makes the soil easier to work.
Begin by cutting down any dead foliage from previous years. Next, using a sharp pointed shovel or spading fork carefully dig around the plant, about 4-6 inches away from the plant on all sides. Push the crown up out of the ground as you work around the plant, maintaining 6-8 inches or more of root growth beneath.
Once the plant is out of the ground use a garden knife to cut the crown into sections, removing dead areas. Keep in mind that larger divisions will re-establish and bloom quicker than small divisions. Preferably 3-5 eyes and a good section of root system should remain with each division, but a minimum of one eye or bud is possible for maximum plant creation. Do not allow the divisions to dry out before they are replanted.
Ornamental grasses often grow from a central crown with multiple growing points and can develop a very thick, tight mass of small roots. If necessary use a shovel, saw or ax to divide the crown. Another technique to deal with plants that have thick, interwoven root systems is to use two garden forks, inserted back to back in the crown. Pry the forks apart, pulling the crown into sections.
Dig the planting hole for each division wide enough for the entire root system. Don’t bend or force the roots to fit into a too-small planting hole. Place each plant in it’s hole at the original planting depth. Add soil around the divisions to fill the planting hole and water each new plant to settle soil around it’s roots.
After division, water as often as necessary to keep the soil moist for the first 10-14 days, then begin to allow the soil to dry out more between each watering. This helps the plant re-establish its root system. Applying a 2-3 inch layer of organic mulch will hold moisture in the soil and minimize weed growth around the new plants. Newly transplanted plants will not bloom well the first year, but should be back to full flower production by the third summer after division.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
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