How to prepare your garden for 100 degrees

Is your garden ready to take some heat? It’s still May (and spring), but the first triple-digit days of 2025 are coming soon.

According to the National Weather Service, much of Northern California – including Sacramento – will be under a “Dangerous Heat Advisory” from 11 a.m. Friday to 11 p.m Saturday, May 30 and 31.

The Sacramento Valley, Delta and foothills can expect highs from 99 to 109 degrees, says the weather service. Overnight lows will be warm, too, staying in the mid 60s or higher.

Sacramento could set records; our record high for May 30 is “only” 100 degrees. Historically, May 31 has reached 105 degrees, Sacramento’s record high for a day in May.

For Friday and Saturday, the weather service declared a “Major Heat Risk” for much of the Sacramento Valley. “Consider canceling outdoor activities during the heat of the day,” the NWS said. “Stay hydrated and stay in a cool place.”

Remember your pets, too. Make sure they have plenty of water and shade. Avoid walking in the afternoon. On a 95-degree day, asphalt can heat up to 140 degrees; concrete can warm to 125 degrees. That’s tough on paws!

But this heat won’t be sticking around, says the weather service. Expect an almost 20-degree drop by Tuesday with expected highs in the low 80s – normal for early June.

This yo-yo weather can be challenging for plants. Take some time now to help your garden cope with the heat to come – as well as more moderate temperatures. Not only will your plants stay better hydrated, they’ll suffer less disease, too.
Follow this advice from the UC Cooperative Extension master gardeners:

* Deep-water trees and shrubs. This helps build their reserves and trains their roots to go deep.

* Deep-water vegetables, perennials and other plants, too. You’re training your plants to grow deep and strong.

* Before deep watering, create water basins around trees, shrubs and many summer vegetables such as tomatoes, peppers and eggplant. A basin holds in extra water just a little longer so it slowly seeps into soil. It’s easy to make a basin: Around the plant, build a soil berm about 3 inches high and at least 1 foot from the main stem (for tomatoes) to 6 feet (for trees). But don’t let water stand against trunks or main stems; that can cause crown rot.

* Mulch, mulch, mulch! Put down a layer of insulating organic mulch (leaves, straw, wood chips, etc.) about 3 to 4 inches deep around trees and shrubs as well as any bare areas in the vegetable garden. Leave a circle open around the trunks or main stems of plants (again, this is to avoid crown rot and other issues). Mulch conserves moisture and keeps plant roots comfortable. Organic mulch (such as alfalfa hay or ground bark) also adds nutrients to the soil, protects soil microbes and controls weeds. What’s not to like?

* Check your sprinklers and irrigation system. Now is the time to make adjustments and repairs. Is every plant getting water? Is it enough?

* Water early in the day. This both conserves water and cuts down on the spread of diseases.

* One good thing about high heat: It wipes out many fungal disease problems. Powdery mildew disappears as the temperature rises.