For much of the US, the summer heat has arrived. But not to worry. Most plants are well equipped to deal with hot weather and will continue to grow if supplied with adequate (not excessive) water. And many plants, especially those native to hot summer climates like the Great Plains, the desert Southwest, the lower elevations of the intermountain West, the tropics and Gulf Coast, actually thrive in heat. However, our gardening practices should shift a bit to make sure our gardens and landscapes emerge healthy and ready for fall once the heat breaks.
New Transplants Require Frequent Watering
For new plants in your yard, frequent watering is a must--even for xeric plants. Plants need at least a full growing season to extend their roots into the surrounding soil where they can find additional soil moisture. So during their first summer, water every 1 to 3 days. (If they begin to look yellow or seem to be in permanent wilt, you're watering too much.)
Water twice. If you water by hand, soak the plant twice (about 5 to 10 minutes apart) to make sure the soil is thoroughly saturated. If you're using a drip system, program it to come on twice, twenty minutes apart. Dry soil will often shed water the first time leaving dry pockets that can kill tender young roots.
Mulch. Make a shallow saucer of soil around the base of the plant and fill it with at least an inch of good quality, coarse textured mulch (NO grass clippings). This is a very, very important technique for insuring survival of young plants.
Suggestions for Getting Your Established Plants Through the Hot Weather.
If you use irrigation on your garden/landscape, don't increase frequency, increase the duration of the watering cycle. Our irrigation mantra is "don't water more often, water more deeply." You want to make sure the water goes down at least 10" to 12" into the soil. Water in the top few inches of the soil will quickly evaporated from the drying effects of sun and wind.
Mulch! In dry heat climates (not the Gulf Coast and other regions with high heat and humidity), shading the soil with at least an inch or two of mulch will greatly reduce soil heat, prevent evaporation of moisture from the soil, and reduce the need for increased irrigation.
Adjust your expectations. When it's exceptionally hot and dry, it's not reasonable to expect your plants will look their best. A don't panic if plants wilt during the heat of the day. Plants wilt to conserve water. But if they don't perk up at night and the wilting becomes permanent, then you've let the soil become too dry and they may die.
Some plants go summer dormant as a copping strategy. Most spring blooming bulbs and some perennials may appear to die. But wait before replanting their spot. They may very well re-emerge later in the summer/early fall when the temperatures drop and it starts to rain again.
Oriental poppies, Prairie Skullcap and Astragalus and many CA native herbaceous plants are examples of this response to extended hot, dry weather.
DON"T fertilize your lawn with chemical fertilizers! If you've not converted to natural/organic lawn care and are still using these chemical salts, ignore what the instructions may say. Summer fertilization promotes thirsty hyper-growth that requires more frequent mowing, a lot more water and will stress your turf often leading to insect problems.
DON"T fertilizer your trees, shrubs and perennials with chemical fertilizers. The same is true as above (except for the mowing part).
For much of the country, our summers are going to continue to get hotter and rainfall will become more erratic. Observe your garden/landscape plants and replace cool season growers that are high water users with more heat tolerant, waterwise (xeric) choices that will thrive with hotter, drier growing conditions. The heat may make these decisions for your by killing off less resilient species. And if your reading my blog, you've come to the right source for these types of plants. Xeric plants have been High Country Garden's focus since the company was founded in 1994.)
Feed ("fertilize") your soil organically in the fall. Top dress your landscape with compost, granular molasses and organic fertilizers after hard frost in fall. Healthy, living soils have a much higher water holding capacity and better water percolation than compacted soils damaged by prolonged use of chemical fertilizers. Granted, this is a longer term approach. But each year you do it, the less you'll need to irrigate during the heat of summer and the more resilient your plants will be to heat stress!
In hot, humid climates avoid planting plants with fuzzy leaves. Perennials like Lamb's Ear (Stachys) and Partridge Feather (Tanacetum) will literally rot above ground when their foliar fuzz is damp and hot.
Plant late summer and fall blooming perennials to bring color back to your yard (and feed hungry pollinators) after the worst of the summer heat has past. There's no reason your post-summer landscape should be without color and pollinators!