April
2007

 

 

By
B. Rosie Lerner
 
Purdue Extension
Consumer
Horticulturist

 

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4-19-07

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Spring Puts the Freeze on Gardens


Indiana gardeners may be used to the ups and downs of spring weather, but spring 2007 has been an unwelcome roller coaster ride!

First, March's unseasonably warm weather pushed many plants to break dormancy earlier than "normal." Then, these plants were caught out in Old Man Winter's last gasp when unseasonably low temperatures -- down to the low- to mid-20s -- fell across the state. Temperatures continued to drop below freezing for at least seven days -- and more than 10 days in some areas.

Around April 8, some areas experienced 24 hours or longer when the temperature never rose above freezing. High winds that accompanied the cold further dried out plant tissue, which was already suffering freeze damage.

The further along a plant's bud development was, the more likely it was to be damaged by the below-freezing temperatures. The lower the temperature drops, and the longer the time spent below freezing, the greater the damage you can expect.

Different plant species vary in their susceptibility to freezing. Many gardeners observed that while magnolias turned brown immediately upon freezing, redbuds appeared remarkably resilient.

Many early spring-flowering trees and shrubs experienced some flower damage, turning their colorful petals brown as toast. For some, the damage may just be brown edges along the petals, while for others the damage may be failure of new buds to bloom.

For fruit crops, every freeze-damaged flower decreases fruit potential. For plants that were in full bloom at the time of the freeze (like peaches and cherries), you should expect a total loss of fruit. If one or two manage to survive, you should consider yourself lucky!

Some apples might have made it through, but remember, we're not out of the woods yet! There's still plenty more weather to get through before we'll know what survives!

Foliage buds generally can resist cold fairly well. But, because of the early warm spell, many leaves had already begun to emerge. The freeze-damaged foliage may have turned brown or black, and may look shriveled or tattered, especially as development continues. Most plants should outgrow this type of damage, and some trees may end up dropping many leaves and replace them with a new set later in spring.

Spring-flowering bulbs, such as daffodils and tulips, are generally used to spring's fluctuating conditions. Even so, many had their bloom times shortened by the severe lows and high winds. On the other hand, many gardeners marveled as some drooping bulb plants perked up as temperatures moderated. Other perennials that emerged before the cold snap, such as bleeding heart, Virginia bluebells and daylilies, may appear scorched and wilted as the frozen tissue thaws, but these hardy plants will survive and will replace foliage as needed.

So what (if any) remedial action should be taken to save freeze-damaged plants? Dead foliage can be removed anytime. Perhaps even more important this year, bulb plants need to retain their foliage as long as possible to be able to make and store carbohydrates for next year's show.

But, as for pruning, we still have several more weeks before we pass the average frost-free date for much of the state. Given the season's unpredictability so far, it would be wise to hold off major pruning chores until you can fully assess this spring's toll. Trees and shrubs may have damage to the young inner tissue of their stems that won't be apparent until summer heat and drought stress bring on sudden twig dieback.

Pruning now also might encourage side buds to develop more quickly, and such young tender shoots will be more easily damaged should we experience another spring freeze. For similar reasons, now is not particularly a good time to promote fast, early growth by applying fertilizer.

As frustrating as it can be, we'll just have to wait and see how the season unfolds. And, if things go bad later this year, we can blame it on the big chill of 2007!

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox