This year has been one of the hottest on record, and next year is likely to be even hotter. As the temperature rises, gardening can become increasingly challenging. There are a few easy things you can do to help your garden beat the heat this summer.
Typically, the first sign of a plant’s heat stress is wilting. No need to panic; immediate watering usually results in a quick rebound. If the plant continues to suffer, however, you will begin to see brown areas and dropped leaves. At that point, the plant may be permanently damaged and require extra care.
Provide the stressed plant with water and shade if possible. Pay special attention to container plants, as they not only get hotter but can be more difficult to rehydrate. Very dry container soil may resist absorbing water at first. You may need to water repeatedly to rehydrate it.
Regarding in-ground plantings, your soil will partially determine how well your plants stay hydrated. Sandy soil drains quickly, whereas clay soil (common in Napa County) retains water, possibly too much for your plants.
The optimal soil type is somewhere in between, rich in humus. Amending your soil with compost or manure will help change its structure to one that is healthier for your garden.
When planning for hot weather, consider that a plant does not have to be in direct sunlight to suffer from heat. A plant may become stressed if the air or soil around it reaches extreme temperatures.
Wind can also be a problem. Despite what common sense or personal experience may tell us, wind will not help your garden stay cooler on a hot day. While a breeze may bring relief to the gardener, it draws moisture from plant leaves, increasing their rate of dehydration.
The key to preventing such problems is proper watering. Where possible, install drip irrigation. The slow, steady application of water will reduce the likelihood of water stress. Drip irrigation also encourages plants to grow deeper roots, allowing them to find water that might otherwise be inaccessible.
Most plants also benefit from mulch. A thick mulch around the plant helps keep soil cool and slows evaporation. Even container plants benefit.
I do a lot of container gardening, and I water my containers by hand. When I know the day will be hot, I prepare my plants with an extreme soaking. During extremely hot periods, I rarely worry about overwatering anything except cacti and succulents. However, that’s not impossible, so check your container soil regularly.
Be aware that hard surfaces absorb heat, raising temperatures around them as the day progresses. Light-colored containers reflect sunlight, potentially increasing the amount directed at your plants. These features can be used to your advantage in shady areas or during cool seasons but can turn deadly during the summer.
I recommend treating plant labels with a skeptical eye. Many times, I have planted something that the label indicated was suitable for full sun, only to watch it shrivel to a crisp in the Napa heat.
Fertilizer can dehydrate a plant, making it more vulnerable to high temperatures. Before fertilizing, be sure the plant is well hydrated and showing no signs of heat stress. I typically wait to apply fertilizer until the cool of the evening.
If you experience significant challenges in a certain part of your garden, consider using drought-tolerant, low-maintenance plants such as succulents, cacti and California natives.
Salvias are one of my personal favorites. I have heard them referred to as “the only truly drought-tolerant plants” (other than cacti and succulents, of course). Once established, which may take about a year, they will have deep roots that help them access extra water when needed. The family is diverse, and nurseries offer salvias with a variety of growth habits and flower colors.
Finally, don’t forget about self-care. Gardening can be strenuous, and you can become dehydrated more quickly than you expect. Start garden work early in the day, and never forget to water yourself!
Free Guided Tree Walk: Join UC Master Gardeners of Napa County in a guided tree walk on Monday, Aug. 7, from 10 a.m. to noon or from 6 p.m. to 8 p.m. Meander through the park as guides talk about its history and share information on 41 different trees. Wear comfortable shoes. Water and restrooms are available. All are handicap- accessible. The book Trees to Know in Napa Valley will be available for $15, cash or check only. Tours depart from Fuller Park, 560 Jefferson Street, Napa. Register online or call 707-253-4221. Walk-ins are welcome but you will be guaranteed a complimentary map if you register at least 48 hours in advance.
Workshop: UC Master Gardeners of Napa County will hold a workshop on “Home Vineyard Part Two” on Saturday, Aug. 12, from 9:30 a.m. to 2 p.m. Learn how to plan for harvest, how to manage vines post-harvest and how to prepare for winter and the next growing season. UC Master Gardeners of Napa County’s Integrated Grape Team presents this workshop. The workshop includes a half-hour lunch break followed by a field trip. Bring a sack lunch and dress appropriately for a vineyard visit. Workshop location is 1120 First Ave., Napa. Online registration (credit card only); mail-in registration (check only or drop off cash payment).
Do you want to become a UC Master Gardener of Napa County? To apply, you must attend an information meeting. For meeting dates, locations and times, or to learn more about the program and volunteer commitment, visit the UC Master Gardener of Napa County website.