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Beware of Jack Frost in your garden

March 28, 2009|By JOE LAMP'L / Scripps Howard News Service

All too often, unseasonably warm temperatures in late winter and early spring can cause problems in our gardens and landscapes. These springlike temps result in many plants and trees breaking dormancy prematurely. A sudden drop to below freezing can wreak havoc on tender new growth. So what should you do if this happens? That depends.

Shrubs

Besides the potential season-ending loss of flowers that bloom on or before June (i.e., azaleas, hydrangeas and rhododendrons), the plants themselves usually fare much better. You may choose to remove dead flower buds (they're gone for the year) for cosmetic purposes. Otherwise, they'll fall off on their own eventually.

Newly emerging leaves on deciduous shrubs may appear burned or blackened or as though they have turned to mush after a late-season freeze. Fortunately, in many cases (and depending on the severity and duration of the freeze) damage is often confined only to the foliage. In a matter of weeks, these leaves will be shed as new growth emerges.

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Newer branch growth and tips are also subject to damage. Once several weeks have passed and potential new foliage growth has emerged, you will be able to see any stem dieback. Working from the top down, prune dead stems and tips back to the first set of healthy leaf buds.

Evergreen shrubs may also exhibit damage, but usually in the newest tissue toward the top of the plant. Older, thicker foliage farther down may or may not show signs of damage. These would include brown or black discoloration or limpness.

Wait to prune back these plants until it is obvious that new growth will not be emerging from the branches. Usually by late May, new growth will have appeared if it is ever coming back. At that time, you can cut back branches to healthy growth.

Trees

Trees respond similarly to shrubs. Although the foliage on your prized trees might look terrible at the time, trees must have leaves to survive. When a late-season cold snap fries the foliage, new leaves will emerge to take their place. In the event tree branches suffer dieback, you may cut them back to healthy growth to improve appearance.

Perennials and bulbs

Some perennials and bulb foliage may take a hit as well. In the case of hostas, go ahead and remove the damaged foliage right away, allowing the new foliage to come on unencumbered. If the foliage has turned to mush all the way to the ground, go ahead and remove it. New growth should emerge.

For Oriental and Asiatic lilies, you might wait a few more weeks to see if new foliage emerges from the top of the plant. Although they may not bloom that year, they will need this foliage to store energy for blooms next year.

This may take a great deal of patience on your part and a willingness to put up with a few "uglies," but don't be hasty cutting everything down or back all at once. Plants need to grow. Putting out new growth is how they recover and continue to survive. Your patience will be rewarded.

Tender annuals

Annuals and warm-season vegetable plants that appear to have melted away will not be coming back. Consider this a valuable lesson learned. There is a reason why you don't put these plants in your garden until after the risk of the last frost has passed.

You can find information on the average date of the last spring frost for your area by calling your local county extension service. This is especially important information for planting tender perennials and annuals. Some years you might be able to cheat Jack Frost, but sometimes he cheats you!

o Joe Lamp'l, host of "GardenSMART" on PBS, is a Master Gardener and author. For more information visit www.joegardener.com.

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