When the heat is on, tomato plants take a break: they don’t care for excessive heat any more than the rest of us. When daytime temperatures are up in the 90s and nights are in the 70s or warmer, tomato plants may keep on blooming, but the flowers often fall off and fruit does not set. Even heat-tolerant varieties slow down when the temperature soars. There are some things you can do to help the plants through the stressful, steamy summer days.
— Mulch helps: a layer of straw, compost, or grass-clipping mulch helps moderate soil temperature, so it doesn’t fluctuate so much. It keeps the surface of the soil just a little cooler than the air temperature, which is better for roots. Mulch also helps prevent moisture in the soil from evaporating quickly, and it helps control weeds.
— Don’t fertilize tomatoes in a heat wave: fertilization encourages plants to grow, but too much fertilizer will produce leafy plants without much fruit. When the temperature is high, you’ll have more plant than the roots can support. Excessive growth also makes plants weak and more vulnerable to damage from insects and diseases.
— Water regularly, but not too much. Tomato plants need an inch or two of water a week, and a deep soaking is better than a little water every day. Regular watering helps prevent tomatoes from developing cracks. Too much water will suffocate plants’ roots. The best way to tell if your plants need water is to poke your finger into the soil.
— Weeding makes a difference: Weeds compete with tomato plants for moisture and nutrients. Pull weeds around plants and mulch after you weed. Avoid hoeing; it can damage the roots of tomato plants, which can cause the leathery brown patches on fruit known as blossom-end rot.
— Pick orange tomatoes. When daytime temperatures are in the mid 90s, tomatoes will not turn red. Go ahead and pick orange tomatoes and let them ripen in the shade on the porch or on the kitchen table.
Once the temperature cools off slightly, tomato plants — and gardeners — will be revived. Tomato flowers will set fruit, and within a few weeks, you’ll be picking tomatoes with both hands.