I’ve said it before, and I’ll say it again. Sometimes I hate summer.
More specifically, I hate high humidity and the mosquitoes that bask in it. And then there are blue-sky-sun-drenched summer afternoons, twilights when flickering fireflies and the heady fragrance of Oriental lilies hang in the still air, and the night sky is studded with more stars than a Broadway stage. Now, those are reasons enough to appreciate summer in Iowa.
And you get tomatoes.
I’ve talked to plenty of gardeners happy to finally see yellow blossoms and fruit set on their tomato plants. Tomato plants can handle heat, but growth naturally slows when days hover in the high 80s and 90s and nights dip back only into the 70s. Yellow blossoms may drop and fruit fails to set with the brakes on.
Excessive heat can cause ripening to slow or stop. Research shows mature green tomatoes ripen rapidly at 68 to 77 F. High temps (85 F or higher) can slow production of pigments that give tomatoes their color.
Mulch will keep soil temperature cooler for roots, reduce weeds, retain moisture and help prevent disease spread.
Water deeply. Too little water can cause cracked skin. Water at the roots, at least 1 inch per week.
Overwatering can suffocate roots when oxygen is unable to percolate through the soil for container-grown tomatoes. Heavy rains, too, can drown plants. Consider moving pots under the eaves.
You have free articles remaining.
Fertilize every other week until fruit sets, then stop fertilizing. Otherwise, you’ll have excessive foliage and fewer fruits (and those will be watery).
Keep a weathered eye for pests and diseases. Take care of problems immediately. Here’s a catalog of common tomato diseases and cures:
Anthracnose: Green fruit can become infected, but usually symptoms can be seen on ripe or ripening fruit as small, circular indented spots in the skin that expand into spots with dark center or rings of spores. In wet, humid conditions, spores give diseased areas a creamy to pink color, decaying the flesh. Discard and destroy plants (fungus survives on diseased vines, in soil and seeds); spores establish themselves on leaf spots caused by early blight or insect damage and can easily spread by rain splash. Wet, warm weather causes the disease to spread. Control measures are the same as septoria leaf spot and early blight.
Septoria leaf spot: Iowa’s most common foliar disease is a fungus that appears as small water-soaked spots which become circular spots with dark edges. Spores look like black specks that watering or rain can spread quickly. Infected leaves turn yellow, dry and wither, then drop. It can attack any time during the growing process. Plant disease-resistant cultivars; leave room between plants for air circulation at maturity; water at roots early enough that plants dry out before nightfall; rotate crops; don’t mess around with plants when foliage is wet or damp to avoid spreading spores; remove plant debris; fungicides also are available.
Early blight: A fungus that appears as black or brown spots that may merge to form blotches or sometimes concentric circles form inside the spots. Spots first appear on lower leaves, which turn yellow and dry up. The fungus may attack fruit, causing black, sunken areas. It spreads rapidly in hot, damp weather, especially after fruit is set. Plant resistant cultivars and harvest all ripe tomatoes daily. Follow the same cultural practices used for septoria leaf spot.
Fusarium wilt: This soil-dwelling fungus attacks only certain tomato cultivars turn leaves yellow and causing wilt upward from the stem. Leaves drop and plants usually die without producing much fruit. Plant resistant varieties; rotate crops.
Verticillium wilt: V wilt can attack more than 200 plant species, including tomatoes, potatoes, peppers, eggplants, strawberries, watermelons and radishes. Yellow blotches appear on lower leaves, which wither and drop, progressing up the stem. Infected plants may survive the growing season but the plant is stunted and yield is reduced. Rotate crops; follow good cultural practices.
Weather/chemical problems: Cracking, thin or tough skin is due to weather conditions; poor and blotchy yellow/orange color occurs when temps rise above 95 or fall below 60. Cat-facing describes deformity at the top of a tomato, when cold weather causes fruit set distortion and kills cells (most common in beefsteak-type tomatoes). Sunscald occurs when green fruit is exposed to the sun, killing tissue and setting up conditions ripe for other organisms to rot fruit.
Tomato plants are sensitive to broadleaf weed killers, too, which can warp and thicken skin. Discard fruit.