tomato
This ‘Green Pineapple’ tomato set only one fruit before the heat set in because I planted it much too late.

July 5th, 2008
Hot Tomato

On June 25th, Carol over at May Dreams Gardens in Indiana is rejoicing that her tomatoes are finally big enough to start tying up. In contrast, here in Austin, Lancashire rose is pulling hers out by June 21st. This is a fine illustration of what Austin gardeners face. While most of the world’s attention concerning tomato season is focused on first and last frost, worrying about setting plants out too early or being disappointed by an early freeze, we southern gardeners face another threat: heat.

If you measure the growing season as the time between first and last frost, then Austin has an incredibly long one. Our last frost is officially mid-March, although many Austin gardeners can’t resist a little gamble and start setting out plants a by Valentine’s Day. Austin’s first freeze often snarls Thanksgiving traffic. But yes, our freezes are short-lived. Our plants don’t go dormant. Our ground doesn’t freeze. So we can have flowers every month of the year.

However, it’s my experience that Austin doesn’t have a marvelously long growing season but two short ones, interrupted by that disaster known as summer. For example, tomatoes set fruit best if the day time highs are below 90F and the night time highs below 70F. Some research shows that “night temperature is the critical factor in setting tomato fruit, the optimal range being 59-68°F”.

In 2008, April was an ideal month for tomato fruit set. The high didn’t get out of the 80s and the lows ranged from 41-72. Within less than a month, the highs were in the 90s and 100s and the lows mostly in the 70s. If you didn’t have your tomatoes in and flowering by April, you missed out. Last year it was October before the temperatures fell into the correct temperature range for tomato set. That leaves a pretty small window before Austin’s first freeze.

I know from reading other Austin garden bloggers that there are a lot of successful tomato growers in this town. Will you share the secret of your success? Do you plant short-season tomatoes? Do you have some favorite heat-tolerant varieties (tomatoes that set fruit in temperatures higher than the average tomato can handle)? When do you put your plants in? And, do you pull them out over summer and start over in the fall? or do you try to nurse them through the heat?