JULY
2012

 

 

By
B. Rosie Lerner
 
Purdue Extension
Consumer
Horticulturist

 

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7-19-12

 

Heat Wave Plus Drought Equals Double Whammy for Gardeners


The early arrival of summer's extreme heat coupled with drought for many weeks now is tough on garden plants as well as their caretakers. Just as flowers and landscape plants have been gasping for water in much of the state, some vegetable crops are also struggling to stay productive.

Tomatoes, peppers, melons, squash, pumpkins, cucumbers and green beans typically drop their blossoms without setting fruit when day temperatures are above 90 F, even if not under drought stress. There's not much you can do except wait for cooler temperatures to prevail. As more favorable conditions return, the plants should resume normal fruit set.

Sweet corn is also likely to have trouble filling the ears in such hot weather. Unfortunately, you only get one flush of flowering with corn. So if your plants just happen to be shedding pollen when the weather is stressful, you can expect poor ear fill with no chance to play catch up later.

Even for those gardeners who have been able to irrigate, many plants will suffer from the extreme heat. In some cases, plants will wilt during midday, despite all your efforts, simply because the leaves are losing moisture faster than the root system can take up water. Plants should recover during evening and morning hours when temperatures are cooler.

Cool-season crops such as radishes, lettuce and spinach no doubt bolted (produced flower stalks) early this year, causing bitter flavors to develop. It's best to remove these crops and replant for a fall crop, when more hospitable weather (hopefully) returns.

If you have made additions to the garden this summer, newly set transplants and seedlings will require more frequent watering and will benefit by shading from midday sun to avoid wilting. You can provide temporary shade during hot afternoons using well-supported fabric, newspaper or similar material; however, this is not feasible in larger gardens.

Extremes in temperature and soil moisture often bring on blossom-end rot, a dry leathery scarring on the blossom end of tomatoes, peppers and squash fruits. Irrigating during dry periods and mulching to conserve soil moisture will help minimize this problem, but some cultivars may show the black scarring despite all the gardeners' best efforts.

Bitterness in cucumbers tends to be more prominent when plants are under stress from low moisture, high temperatures or poor nutrition. Most cucumber plants contain a bitter compound called cucurbitacin, which can be present in the fruit as well as the foliage. Sometimes cutting away the stem-end of the fruit will remove much of the bitterness. Frequently they are so bitter throughout that it is best to compost and hope for a return to more favorable conditions for subsequent production.

Container plants on the patio will really be stressed during extreme heat, since their soil temps are going to be considerably higher than those in a garden bed. In addition to watering more frequently in hot weather, provide afternoon shade to help keep them a bit cooler.

Surely this extreme heat won't last forever - it just seems that way right now! In the meantime, try not to overdo the garden work. Aim to complete your chores very early in the morning or in the evening when the sun is less intense. Take frequent breaks and drink plenty of water to keep yourself from wilting.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox