Late Summer And Fall Tomatoes Challenging Says LSU AgCenter Horticulturist

Thomas J. Koske  |  4/19/2005 10:28:40 PM

News You Can Use For July 2004  

Producing tomatoes in the summer heat is tough. When night temperatures get into the lower to mid 70s, most tomatoes can’t pollinate properly and their fruit won’t ‘stick,’ says LSU AgCenter horticulturist Dr. Tom Koske.

When pollination fails, the flowers drop, leaving an empty truss. From flower drop to picking is only about 40 days in summer heat – if you can get fruit to set.

Some cultivars have been bred to tolerate a little more heat and still set fruit. The best choices are Sunchaser, Sunleaper and Florida 91. Heatwave, Solarset and Sunmaster also have done well at this time. Celebrity produces fairly well but tends to crack a lot in hot weather.

For best success, Koske advises starting your own plants from seed in early summer. It may be difficult finding the best heat-tolerant varieties as transplants; but if you can, it is always best to diversify cultivars to ensure some production in this difficult season. Transplant by late July or don’t bother.

Set transplants a little deeper than in spring gardens to access cooler soil and better moisture. Use a ‘starter’ fertilizer with high phosphorus (the middle number) and continue to keep up the fertility with extra nitrogen to develop more foliage. This covers the fruit better and reduces sunburn damage. Provide little or no pruning to maintain this thickness.

Other gardening problems are magnified in summer. By then, insect populations have built and diseases may be more prevalent. Keep up a good pest control program or you may lose a lot of fruit before it’s ready for harvest.

Koske says water management is another key factor. "Provide good drainage for those heavy rains. Wet feet, followed by bright sun, will scald the leaves," he says.

Allowing plants to dry down too much hurts yield, induces blossom-end rot and sets the fruit up for more cracking. A good cover of organic mulch is especially important at this time and helps to provide more uniform soil moisture. Try to water in the morning to offset the extreme afternoon stress.

For related topics, look for Gardening and Get It Growing links in the Feature section of the LSU AgCenter Web site:  Additional yard and garden topics are available from an extension agent in your parish LSU AgCenter office.


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Source: Tom Koske (225) 578-2222, or

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