We’ve had a couple of weeks of unusually, blissfully cool weather this July. Normally in July, long extremely hot days and short hot nights cause vegetables and fruit and nut trees to enter into a state of semi-dormancy during which growth and flower production slow or stop. Cooler day and night temperatures in early July meant that tomato and cucumber flowers did not fall off the vines, peaches ripened slowly, increasing sugar content and flavor, and corn ears developed a full set of plump, juicy kernels.
As high temperatures reappear, we need to be monitoring soil moisture content daily in our vegetable gardens and home orchards. Consistently moist soil at the root zone will help prevent or reduce several problems caused by high heat and water stress. With good irrigation practices, we should be able to save and harvest the bonus fruits and vegetables that set in early July.
Blossom end rot in tomatoes is caused by a combination of a calcium deficiency in the soil and water stress. Feeding tomato plants a couple of tablespoons of bone meal every two to three weeks should raise calcium levels in the soil enough to reduce blossom end rot problems in later-season tomatoes. Blossom end rot in melons, squashes, cucumbers, eggplants and peppers as well as peaches and other fruits results primarily from uneven, inconsistent irrigation. The blossom (bottom) end of the fruit turns gray or black, sunken and mushy; the rest of the fruit is still edible. Water stress also affects the taste and texture of cucumbers and melons, making them taste bitter and drying out the flesh inside. Corn kernels inside the husks don’t fill in completely and also dry out when irrigation is insufficient or uneven.
Cat-facing or skin cracking in tomatoes occurs during hot spells when the skin can’t expand as quickly as the flesh inside. Consistently moist soil will help prevent cracking. Sometimes a mold or rot will develop along the skin cracks, but our dry summer climate tends to retard the development of molds and fungi.
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Tomato plants need about 7 gallons of water a week in summer here. Irrigate tomatoes when the top inch of soil is dry, watering slowly and deeply to completely soak the roots which can extend down 12 to 18 inches. Smaller drip emitters don’t always provide enough water to plants during the summer months. Consider installing larger emitters or use bubblers on a hose to deep irrigate (on mandated watering days, of course) and increase watering times.
Cucurbits (melons, squashes, cucumbers) may need daily irrigation during hot spells. Water them when the top inch of soil has dried. Corn plants grown in rows will need supplemental water when the top 2 or 3 inches of soil is dry; increase watering times, especially if you’re flooding the furrows to irrigate.
Fruit and nut trees, including citrus, may need deep irrigation every four to five days during the hottest weeks when the top 3 to 4 inches of soil is dry. Bubblers on a hose, soaker hoses and small oscillating sprinklers can be used to soak the roots at the edge of the canopy to at least a depth of 12 inches.
Send Elinor Teague plant questions at firstname.lastname@example.org or email@example.com (“plants” in the subject line).