Louisiana summers are a tough time for tomatoes to set and hold fruit. The
heat causes irregular flower growth in most cultivars, and the result is
poor fruit set, according to
horticulturist Dr. Tom Koske.
"It is true that some cultivars are now available that have genetics to
beat the heat, but they still won't do miracles," Koske says, adding, "We
can, however, help them to do their best with the proper culture."
Assuming you have fertile soil and are controlling pests, you can follow
four treatment practices found effective in LSU AgCenter research plots.
These techniques give heat-set tomatoes their best chances to develop
First, choose summer growing tomatoes that have the heat-set genetic
makeup. These include Sunmaster, Solar Set, Heat Wave, Sunchaser, Sun
Leaper and Florida 91. If you have trouble finding the cultivars you want,
get into the habit of starting your own from seed a month or two ahead of
time. At this time of year, no greenhouse or frost protection is needed.
Second, plant deeper than usual. Normally transplants are set to just cover
the root ball. For a summer crop, plant deeper to access cooler soil and
better soil moisture. In fact, shallow planting may even be lethal at this
time of year. Set plants in 6-inch-deep holes, up to about the first true
Third, water in the mornings. LSU AgCenter research plots were watered
every other day, unless it rained, but the home garden must be watered
according to soil needs. Water so that root zones are neither too soggy nor
too dry. Morning watering is thought to keep roots cooler and plants less
stressed than in the hot afternoon.
Fourth, mulch plants well to cool roots and even out soil moisture.
Research revealed that a white or light-colored mulch was much better than
the black plastic that works so well on spring tomatoes. Dark mulches get
too hot in the summer.
All these treatments combined yielded significantly more summer fruit and
bigger tomatoes in the research fields. For more on these topics, see our
AgCenter information on tomato pests and publication 1902, Growing Tomatoes
in the Home Garden. For related topics, click on the Lawn and Garden link
at the LSU AgCenter Web site,