By mid-August, nighttime temperatures should cool into the sixties. Longer nights and cooler if not cool nighttime temperatures will allow plants to begin to recover from heat stress that slows or stops growth and flowering during the summer.
There’s no need to fertilize in July in our climate when really high day and nighttime temperatures cause plants to enter a state of semi-dormancy. But in mid- to late-August, we can usually resume a regular fertilization schedule. We’ll need to reconsider our fertilization program this year in view of the continuing drought and severe water shortages.
Fertilizing food crops for continued production is a priority. Vegetables that stop setting flowers in high heat (i.e., tomatoes, squashes and beans) will begin to produce flowers again in just a couple of weeks. We normally recommend giving all food crops a light feeding in mid- to late-August at half the recommended rate of a low-number granular fertilizer (such as a 4-5-3 formulation) and continuing to feed monthly into October. This year, because the drought will have seriously stressed all plants, give food crop plants just 1/4 the recommended amount. That may be just a tablespoon of some products. Whatever fertilizer you use, check labels for feeding amount recommendations and lower the amounts by at least half.
Feeding stressed plants with lesser amounts of fertilizer will be less likely to encourage rapid growth spurts of tender new leaves and flowers that can be scorched by high temperatures.
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Low-number organic granular foods leach nutrients into the soil at a much slower rate than high number or liquid chemically-based fertilizers, providing a more consistent nutrient level over a longer period of time. These types of fertilizers also contain beneficial soil microbes that improve the soil’s ability to hold water and improve plants’ roots ability to draw up water-very important when water is scarce.
Fruit and nut trees, except citrus, are usually fed with a high-nitrogen fertilizer after harvest to replenish the nitrogen that is lost when the crop is picked. This year, it’s recommended that we wait until leaf fall in November to feed fruit and nut trees to give them a boost just before they enter winter dormancy. If the rains have begun to fall in November, we can feed fruit and nut trees at the normal amounts. If the soil is still dry, we’ll need to cut back or curtail fertilization this fall.
Most flowering plants will survive without late summer and fall feedings. Roses bloom reliably four to six weeks after each fertilization and the best rose crop of the year (no bugs) appears in late September or early October, following a mid to late August feeding. Roses are some of the most hardy and resilient plants as are other drought-tolerant and native plants.
Camellias and azaleas are usually fed monthly during the summer, except in July. Camellias and azaleas that are planted in nutrient-rich, well-draining soil and that are heavily mulched will do well without feeding. Feeding really won’t help some plants that really aren’t suitable for our climate, like hydrangeas. Replacement is the best solution.