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August is time for dividing and transplanting perennials

August is the month when we need to make decisions about the plants in our flower beds. With the abundant rainfall this season, our plants have often expanded their boundaries, not only with blossoms, but their foliage is thick and lush and green. So many perennials probably need to be divided and transplanted. Late August through early September is an ideal time to transplant flowering perennials because the temperature is becoming cooler (especially in the night) and they will have a month to six weeks to establish their new root system. Also the top of the plant is no longer growing and the plant puts all its effort into developing the root system before freeze up.

Perennials usually need to be divided every three to five years. If it has been an especially good year like this season, they may need dividing more often. If your perennial has fewer flowers than usual or if the center of the plant seems to be dead, it is time to divide it. Take transplants from the sides of the perennial that look new and vigorous. Replant sections should be at most 20 to 25 percent of the original plant. Smaller sections grow more vigorously and tend to produce stronger, longer-lasting flowers.

Perennials like peonies (plant peony eyes only 1 to 1 ½ inches deep), lilies, iris, phlox or most of your flowers which have bloomed during the summer do well if transplanted now. Fall blooming mums and asters do better if they are transplanted in the spring. Hostas and daylilies are tough plants and can be divided and transplanted almost anytime. Plants like clematis, delphinium and trillium have a tap root and do not like to be transplanted. You are better off going to a garden center and buying them.

Some points to keep in mind when dividing and transplanting perennials:

• The day before you plan to dig up and divide the perennial, water it well so the roots are not dry.

• Take twine or string and tie around the clump that you plan to dig out. Also cut back the foliage to about half. The roots cannot support the foliage and need to put all their effort into establishing the new root system.

• The best time to dig out your perennial is late evening when the sun is going down and it is cooling off.

• Spade down at the drip line of the plant because the root system usually extends out this far and this will get most of the root system. This spading should be down and at an angle around the outer edge of the section. Spading down at an angle will enable you to lift the clump. Last spade straight down through the center or section you are dividing out. Then go back to the outside or drip line, and with the shovel at an angel, lift out the clump.

• The new hole you place the division in should be deeper and wider then root system you just dug out. The soil in the hole should be worked up well so it is easy for the roots to begin to grow. Put compost in the bottom, place the divided perennial into the hole and fill the hole half way with soil and water well. It is good if the water has a root stimulator solution in it. Fill the hole the rest of the way, firm the soil around the transplant and water well. It is good if there is a slight dip around the plant; this will act as a dish to hold water and rain. Watering is also important because it gets rid of air pockets around the roots.

• Also remember the hole that you dug your clump from. Whatever amount of soil you dug out of your garden should be replenished with soil, compost or organic matter. If the hole is left, the area around the remaining plant will settle and there will be drying out of the exposed roots. This puts the parent plant at a


• Check on the transplant each day for a couple weeks after it has been moved. It may need some water. Usually the foliage really dies back and it looks pretty bad. But what is important at this point is root growth and establishment. Mulch should be applied about three to four inches deep around the plant. Pull the mulch back about four inches from the base of the plant. Last mark what you transplanted because come next spring you may not remember what you transplanted.

Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.