May 7, 2011 in Washington Voices

Tomatoes are fair weather growers

Pat Munts

The tomato is almost the universal garden vegetable. Ask any gardener, beginner or veteran, what will be in their vegetable garden and the tomato will be on the list. To get that perfect tomato, though, takes some determination to outwit the weather.

We have a short growing season. Our last frost date is May 15 and our first fall frost date is around Sept. 15. Because tomatoes are frost sensitive they usually aren’t transplanted out in the garden before the end of May, which gives us about 75 days to grow a plant to maturity. That means we have to plant tomatoes that can ripen in 75 days or less according to the label. Unfortunately many of the popular tomatoes, including heirlooms, don’t mature that quickly.

Another challenge is that tomatoes need at least 55 degree nights to set fruit. We don’t generally get those temperatures until mid-July through mid-August, a fairly short window of opportunity. So even if we get warm days, cold nights will set back flower production. Buying that large, blooming plant in May won’t get you fruit any earlier. The plant will just drop the flowers.

Lastly, our June weather is iffy enough that plants sometimes can’t mature enough to be ready to flower by mid-July’s warmer days and nights. Last year June was cold and wet and that set back many plants to the point that they weren’t ready to flower when the heat arrived. It took another two to three weeks for them to catch up, and by then the warm part of the summer was waning. Thankfully we had a long, warm fall to ripen them up. Unfortunately, this year is beginning to look like a repeat of last year.

That said, we do get good tomatoes here. We just have to plan ahead and be ready for the weather we get. First, plant only transplants that will ripen in 75 days or less according to the tag. Second, resist planting them until the end of May. If you buy them early, keep them in a protected spot where you can whisk them into the house if a frost threatens, or just keep them indoors under lights.

Thirdly, keep the frost protection handy and watch the weather reports for frosty forecasts even into June. You might even consider covering them with a floating row cover – a spun polyester white fabric that resembles interfacing material used in sewing and is available at better nurseries or garden stores or online– for all of June.

Lastly, once the warm weather begins cooling in late August, cover the plants again to hold heat and ripen the fruit.

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