Saturday, October 22, 2016 By: Ask A Master Gardener

Dividing Perennials in Fall

Perennials give clues when its time to divide, replant

Brian Jervis: Ask a Master Gardener

Saturday, October 22, 2016

Q: When should I divide my pampas grass? What about my iris? G.W., Tulsa
A: Pampas grass is a perennial, a class of plants in which the tops die back in winter but re-emerge from roots in spring. A general rule of thumb for dividing and replanting perennials is that it depends on the time of blooming. For those blooming in spring, fall division may be best, and for those blooming in summer and fall, divide in spring (or after fall blooming is completed).
There are many types of perennials, and not all fit into the above recommendations about when to divide. Some do best not divided at all, unless new plants are needed.
Perennials will often give you clues as to when they need dividing. With increase in density of the root system, the center of the root ball often dies so the plant may have little or no growth in its center. Also with crowding of the roots, the whole plant simply doesn’t perform as well, with substantially less growth and numbers of blooms. Another reason to divide is if the plant has simply outgrown its space.
As to when to divide Pampas grass, it seems to do best divided in the early spring after the dead foliage has been cut back to a height of 6 inches or so. Like many other perennials, the whole root ball can be dug up and cut into pieces or sections of the roots removed while the remainder stays in place. In any case, many of the grasses, and especially Pampas grass, have extremely tough root balls and an ax will usually be needed to divide.
Perennials like black-eyed Susans, purple coneflowers, monarda and yarrow can be divided in either spring or fall, while asters, blanket flower, bleeding hearts, cannas and chrysanthemums do best if divided only in spring. Iris do best if divided at least a month after they complete spring blooming.
Plants that often need no division, unless new plants are needed, are hostas and peonies. Peonies are a little difficult to divide and replant in the sense that they must be replanted at the proper depth and, in some cases, may take 1-3 years before beginning to bloom again. Peonies should be dug up and divided in September or October.
When dividing, plan ahead. Water the plant and dig its new hole, if moving it, beforehand. Adding organic compost to the native soil at replanting is beneficial in all types of soils. When transplanting, take care to not let roots dry out; a cloudy day is best.
A benefit of dividing plants, other than improving their health, is that you will end up with several new plants to share with friends and neighbors.
For more information as to the time to divide and how to do it, consider going to the Clemson University Extension website and search for “dividing perennials.”

Garden tips

  • ·       Plant container-grown trees and shrubs this month. Fall is generally the best time to plant. At this time, the plants have no energy drain to produce leaves and can concentrate on growing a root system until the soil gets cool in winter. They are better prepared for spring growth if planted in the previous fall.

  • ·       Check and treat houseplants for insect pests before bringing inside. Look at the roots and repot those that are rootbound. Irrigate the soil thoroughly before bringing inside. Spray with horticultural soaps or oils if there is evidence of insects.

  • ·       There is still time to plant radishes and mustard in the fall garden.


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