Purdue Extension Service

Vanderburgh County, Indiana

April Frost, Home Show

By Larry Caplan, Extension Horticulture Educator, Vanderburgh County, IN

For the Evansville Courier and Press, April 8, 2007

Over the last couple of nights, the temperatures sank low enough to cause concern among many gardeners. I don't want to call this a "late frost," because our average frost-free date for southern Indiana is April 6 through 15. Since spring began almost 3 weeks early, it just seems late.

Within the next couple of days, we should be able to see exactly if any damage occurred. Tender flower and vegetable transplants will probably be the hardest hit. If they weren't protected, they may have brown or black dead areas on the leaves, especially along the edges. These plants will probably be stunted slightly, but they should come out of it.

Fruit trees that were in bloom probably had some blossom-kill. However, most fruit trees put out many more flowers than the tree can support, and so thinning is often required. I would say this cold snap acted more as a thinning agent than anything truly damaging. You may want to look closely at your strawberry blossoms, though. If the blossoms have a black center, that flower is dead and will not produce a fruit. We may have lost some of our earliest berries, but the plants themselves should be OK, and will still produce a good crop this year.

I am still getting calls from people who are seeing yellow or brown foliage on their broadleaf evergreen plants. I've seen this injury on hollies, magnolias, viburnums, and boxwoods; I've even seen something similar on a couple of eastern red cedars. This is all due to cold injury the plants suffered back in February. If you'll remember, we were in shirt sleeves much of January and early February. The temperature then dropped significantly when we had our only major snow of the year. This sudden shift from warm to cold weather damaged the exposed leaves of these evergreens.

These leaves will continue to turn brown and drop. However, the twigs and branches are still alive, and I fully expect these plants to leaf back out as normal within the next few weeks. So, hold off on your pruning of plants that you think may be dead, because chances are, they're not.

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The Extension office and the Master Gardeners will be hosting a booth at this weekend's Home Show. As I write this, we are slated to be stationed at the entrance of Gate 3 at Roberts Stadium. In case something happens at the last minute, check the other gates for us.

We will be displaying information about the Emerald Ash Borer, the insect that's giving us "tree-huggers" fits. We will also have some information on upcoming events, including the Master Gardener plant sale of May 12 and 13, and our Garden Walk, scheduled for June 16 and 17.

Please stop by. Bring us your sick plants, and we'll try to diagnose them for you!