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Larry A. Sagers
The incurable curly top virus affects tomato plants. Symptoms are curled or upside-down leaves.

If the weather has you confused, think what it must be doing to your plants.

The cool, moist spring suddenly turned hot with a vengeance. In early June, plants thought that they had emigrated to Seattle, London or someplace besides our desert. Likewise, tomatoes, peppers and many warm-season flowers pouted as they waited for warmer temperatures to help them grow.

Of course, what happens in the garden is always weather-related. The trick is to determine what is happening and how it affects the plants. Is it a temporary problem or is it something that can have serious, life-threatening consequences for the plants?

Let's start in the vegetable garden to check what is going on there.

The delineation here is between warm-season and cool-season vegetables. Any cool-season crops (peas, carrots, beets, lettuce and other vegetables) that were planted early liked the spring and probably produced good crops, providing they germinated in the cool, moist soils.

Some of these crops don't like the heat. Temperatures in the 90s often cause them to bolt or flower and go to seed. Even if they don't bolt, they usually turn tough and bitter, and the quality drops to the point they're not worth eating. Cabbage heads often split.

Warm-season vegetables got off to a slow start. The first problem was getting the seed to germinate. Many warm-season crops will not germinate until soil temperatures reach 55 degrees, and many require soil temperatures of 75 degrees or more. That doesn't happen when temperatures repeatedly drop into the 40s at night.

After getting warm-season crops to germinate, they still might not be happy. If you purchased transplants, they might have been sitting in the soil without growing much for several weeks. Now that it is warmer, they are finally starting to grow and hopefully should start producing soon.

One problem I have already seen hitting the tomatoes is curly top. This is a virus disease spread by the sugar beet leafhopper. The symptoms show as curled leaves that roll or turn upside down. The leaves turn yellow and the veins on the underside of the leaves are purple. If there is fruit, it ripens at whatever size it happens to be. There is no cure.

When the plants start to bloom, you might find another problem. All tree fruits and vegetables that produce a fruit have to be pollinated. While tomatoes, corn, peas, beans and several other crops are pollinated by the wind, most require bees to help the process.

For your fruit trees, either the bees were there or they weren't, and it is too late to do anything about it now. The crops to watch are melons, squash, pumpkins and cucumbers. If you get blossoms but no fruit, you might do some hand pollinating by transferring pollen from the male blossoms to the female blossoms that have the little fruits attached.

Moving into the rest of the landscape, take a look at the trees. If you have London Plane or sycamore trees, they might be lacking their leaves. The culprit in this case is a fungus called sycamore anthracnose. The disease attacks the buds as they start to open. It then spreads into the wood. This causes the twigs to die and prevents leaf development.

Prevention is the key. Once the fungal diseases develop, it is too late to effectively control them. Fungicides are only effective if applied before the leaves unfold. Fortunately, these trees are resilient and will send out new, healthy leaves once the weather turns warm and dry.

Your aspen trees might show similar problems now — or even later — in the summer. Aspen leaf spot is another fungus that causes the leaves to develop dark spots that sometimes expand until they turn totally black. Any treatment after the spots appear is useless, so save your time and money.

Evergreen trees are making some homeowners nervous because as the new foliage emerges, the old needles look pretty rough. They survived drought and heat last year and look a little dry and discolored. Look at the new growth. If it is healthy and green, the trees are probably be fine.

Lawns are a whole different matter. Those who were complaining about mushrooms growing in their lawn a few weeks ago are now complaining about huge brown areas appearing like alien landing spots. The majority of brown spots are the result of improper watering. Check your sprinkler system, and also check the water penetration to make certain the water is going into the soil.

Fortunately, while most of our plants were happy for the moisture and cool air, most are also adapting to the normal summer temperatures. Nature has a way of helping them compensate and thrive in spite of our complaints. So get out and enjoy growing your garden!


Larry A. Sagers is the horticulture specialist, Utah State University Extension at Thanksgiving Point.