Do you know what’s good about a heat wave in July? The tomatoes love it! I returned from England to tomatoes sprawling everywhere. I pounded nearly 3 dozen wooden stakes into the ground and used up an entire spool of twine wrestling them into shape over the weekend.
Once your tomatoes are properly staked, the next thing to do is open prune them. At the crotch of every leaf is a sucker. These will turn into new vining branches, eventually clogging up the plant. What you want to do is remove some of the suckers to allow air to flow through the center of the plants.
High humidity, lots of rain (even tiny amounts all the time) or overhead watering (a total NO NO for tomatoes) will cause the plants to develop leaf spot fungus. Fungus looks like black blotches/spots on the leaves; often those spotted leaves turn yellow. I put on rubber gloves and cut them out of the plant, throwing them in a garbage bag, not in the compost. Then I wash my pruners and my gloves in rubbing alcohol to clean them. If the disease continues to appear, or if you have had to remove a lot of leaves, you should spray the plant with liquid copper to kill any fungus spores. You should also spray the mulch at the base of the plants. If you don’t have fungus, but have dealt with it in the past, you can spray your plants with BioSafe hydrogen peroxide spray to prevent fungus from happening.
If you notice just a few yellow leaves, especially on the bottom of the plants, prune them off. They are probably due to lack of water or lack of feeding. I deep soak my established plants a couple of times a week during 90 degree heat waves. You can feed your tomatoes with Coast of Maine Stonington Blend granular fertilizer or you can feed them with Neptune’s Harvest Tomato and Vegetable liquid fertilizer. Your choice, depending on if you would rather sprinkle and scratch it in or water it in. If you don’t have mulch around your tomato plants, you should, as it keeps the soil moisture levels much more even which helps to prevent blossom end rot. Add more mulch if it has broken down and is getting thin. At Natureworks we use Lucerne Farms chopped hay which has been sterilized to kill weed seeds.