Our long hot dry summers really take a toll on our plants and lawns. Many gardeners in the Central Valley made significant changes to their landscapes during the last four severe drought years, taking out thirsty lawns and planting non-native and heat and drought-tolerant plants. Ours is a desert-type climate but we’re still creating English cottage gardens and planting tropical and semi-tropical plants surrounded by lush green lawns that really suffer in the summer heat.
In other milder climate zones, summer fertilization is key to maintaining the health and vigor of plants and lawn grasses. That’s a problem for us. Daytime and nighttime temperatures during July and August are so high in the Central Valley that most non-native plants or those that are not heat and drought-tolerant go into survival mode. They become semi-dormant, slowing and even stopping growth and flower production, to conserve energy.
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It seems contrary to common sense to slow or stop fertilizing the roses and the fescue lawns in our gardens during the hottest months, but that’s exactly what we need to do.
Here are a few guidelines for changing fertilizer types and reducing fertilizer application amounts and timing in July and August.
Lawns – Warm-season lawns including bermuda grasses thrive in heat but even they will slow growth in summer. They can safely be fed monthly in July and August at half the recommended rate.
Cool-season lawns like fescue are naturally dormant in summer and winter and need need no fertilization during the next two months.
Newer lawn food formulations have reduced nitrogen amounts (usually somewhere between 9 percent and 29 percent) and have added iron to help keep grasses green. Since nitrogen forces rapid new green growth, these lower-nitrogen fertilizers would be a good alternative to apply to less actively-growing Bermuda lawns in summer and to fescue or cool-season lawns in fall and spring.
Roses, flowering annuals and perennials – Most flowering perennials stop producing new buds and leaves in our summer heat. Petals are thin and papery, colors are faded and fragrance is much less intense. Adjust amounts to plant size and dig in a tablespoon per petunia plant or a half cup per rose bush of a good quality compost instead of a commercially-formulated fertilizer. Compost has much lower percentages of nitrogen (1 to 3 percent on average) but is chock-full of micro-nutrients and beneficial fungi that attach to roots, increasing the plants’ ability to draw up water and nutrients.
Summer vegetables, fruit and nut trees – Heat also slows flower production in the vegetable garden and causes flower drop. On really hot days, bees and other pollinators try to stay cool rather than forage for pollen and nectar. Discontinue fertilization of summer vegetables and instead apply a half cup of compost per plant monthly during the hottest weather.
Fruit and nut trees should be fed once with a higher-nitrogen fertilizer after harvest. Wait to feed until temperatures begin to cool in mid-August or apply the same lower nitrogen lawn food you’ve been feeding your Bermuda grass.
Send Elinor Teague plant questions at firstname.lastname@example.org.