Growing Tomatoes in Hot Weather

 

Mid-summer will often bring problems for tomato plants, which can affect fruit production as well as quality. Some of these problems can be attributed directly to the weather. Tomato plants do best when the daytime temperatures are between 65-degrees and 85-degrees Fahrenheit. When the daytime temperatures are consistently above 90 degrees, growth slows down and fruit set stops. Leaves will begin to curl in response to the stress of high temperatures.  The plant does this to reduce the surface area and slow down loss of moisture. During this time, tomato plants can still be productive if you practice good watering habits, add mulch around the base of the plant and provide some shade. Best practices for watering tomatoes include a regular deep, thorough soaking at the base of the plant. Water slowly, allowing the water to soak in five or six inches. Avoid overhead watering, as this can encourage disease problems. Water in the early morning, before eight.  Adding two to three inches of organic mulch around the base will stabilize the ground and reduce moisture loss. Mulch acts as a moisture regulator and when combined with slow, consistent watering will help reduce instances of blossom end rot; a condition caused an insufficient or inconsistent supply of Calcium. Consistent moisture is critical, whether you’re growing tomatoes in beds or in pots.  Blossom end rot is one of the most common problems with tomatoes.  It appears as a dry, leather-like patch at the base of the fruit.  

Blossom end rot can occur in peppers and eggplant, too. To supplement the calcium supply, apply a liquid calcium directly on the leaves and fruit, using ferti-lome Yield Booster. Concentrated 20% Calcium is also available and can be applied as a foliar spray or a root drench. 

Providing your plants some shade will also help improve yields. When temperatures get above eighty-five to ninety degrees Fahrenheit, tomatoes on the vine won’t ripen. Temperatures this high will retard or prevent the production of the red pigment lycopene. Covering them with shade cloth will reduce the temperature and encourage fruit to set, as well as ripen. 

Other problems encountered this time of year include cat facing, zippering, late blight and insects. When the tops of the tomatoes crack, it’s called cat facing. Zippering appears as a scar resembling a zipper. Cat facing and zippering are disorders that occur early in the fruit formation cycle.  There is no cure so the best thing to do is to remove any fruit that exhibit cracks or zippering. Two major insects to watch for now include tomato horn worm and Western Flower Thrip.

If you notice a sudden defoliation of your plant, accompanied by black droppings on the leaves, most likely there’s a tomato horn worm eating its way through your plants. They’re very well camouflaged, but if you look carefully, you can find them and pick them off. You can also apply organic insecticides containing Bacillus thuringiensis (subspecies kurstaki).  These products can be used safely and effectively to control horn worm. 

If you start seeing leaf curl and the fruit on your plants takes on a blotchy appearance, it’s almost certain your plants have Tomato Spotted Wilt Virus, a disease vectored by Western Flower Thrip. Spinosad is a good choice to control thrip. 

When it comes to growing tomatoes, many factors can influence fruit quality and production. If you’re not sure what’s going on in your garden, bring us a sample of the leaves or tomatoes to The Flower Bin Diagnostic Center. We’ll figure out what’s going on and come up with solutions that will ensure you know what to do to get the best from your tomato plants.