UNIVERSITY PARK, Pa. -- There Isn't A Lot You Can Do In A Pennsylvania Flower Garden On A March Day, Even If It's Sunny And Warm. But A Penn State Horticulture Expert Recommends Spreading Mulch To Delay Plant Emergence As Long As Possible.

"You have to keep the soil temperature as cool as possible to delay spring flowers and perennials," says Robert Berghage, associate professor of horticulture in the College of Agricultural Sciences. "A good layer of loosely packed mulch can insulate against temperature fluctuations. Don't mulch too heavily, because a dense mulch will smother plants. A layer of dry leaves would be ideal."

Berghage explains the loose mulch will protect the tops of emerging shoots from rapid temperature changes that still may occur. "If emergence has started, even temperatures below freezing for an extended period usually will not damage the actual flower stalk, which is deep into the bulb at that point," Berghage says.

Trees and shrubs that have begun flowering will retain some dormancy as long as there are no extended warm periods. If the trees do flower fully too soon, Berghage says it's unlikely the tree will bear fruit later in the season.

"Pollination will be poor or nonexistent in most cases because insects and birds aren't really active yet," Berghage points out. "If a freeze happens, that can prevent fruit as well."

Berghage says plants in protected locations close to buildings, pavement or stone walls -- all of which concentrate heat -- will continue to grow and not much can be done to delay growth.

"Keep track of the plants that have significant vegetative or flower-bud injury," Berghage suggests. "In the summer these injured plants should be watered more so stress on the foliage is reduced and the plant can generate food for the next growing season."

If a bulb plant fails to flower this season, Berghage emphasizes that gardeners should let the plant follow its normal life-cycle. "Often gardeners will mow off the leaves if the plant fails to flower," Berghage says. "If the plant's foliage is not allowed to go through the growing season, the plant will be weakened and might not produce quality flowers next season or ever."

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EDITORS: Contact Robert Berghage at 814-863-2190 or e-mail rdb4@psu.edu.

Contact:

Jeff Mulhollem jjm29@psu.edu 814-863-2719 814-863-9877 fax #125