Plant care tips for gardens during a heatwave in California
It looks like another triple-digit wall of heat is hitting Southern California this week, so it’s time to act now to protect your unsuspecting plants, which are just emerging from the relatively mild temperatures of spring.
Outdoor potted plants are particularly vulnerable, as they can dry out very quickly, but at least you can move a potted plant to a more shaded location. Plants in the soil should wince and endure it.
The goal? Avoid destruction such as that caused in July 2018, which is only too fresh in some memories: an explosion of heat raised triple-digit temperatures overnight, burning fruit on the vines, withered leaves and flowers crispy in Southern California.
AT Descanso Gardens, for example, where the temperature rose from 74 to 114 degrees in a single day in July 2018, most of its legendary camellias were damaged by sunburn, said Rachel Young, director of horticulture and plant operations. gardening at the La Cañada Flintridge site. With proper care, the staff were able to treat them.
But fruit and vegetables on the vine? Not so lucky.
“I had grapes at home that were pretty much ripe,” she said, “but that night they were raisins, and I don’t like raisins.”
It was the same month that my friend smugly texted me from Portland, Oregon, gloating over how he missed the heat wave, until he came back and inspects the wreckage around his house. from Pasadena.
“I lost a lot of plants in my garden,” he wrote. “Very upsetting. Blow with a blowtorch.
Scorching temperatures can be devastating to the garden, but there are ways to save and protect your plants from the scorching heat, say Young and Yvonne Savio, retired director of the Los Angeles County Master Gardeners program, who speaks now gardening and shopping. jardininginla.net.
Here are their tips for dealing with the heat, but remember: take a hat, a lot water and your own sun protection gear before heading out to the garden.
1. Deep water
Slow, deep watering at the base of the plant is the best preparation for excessive heat, as it drives the roots deeper into the soil. “Plants are like people – they get lazy,” Young said. “If they are given water for 5 minutes each day, they keep their roots close to the surface, so by watering deeply, you are training the plants to send their roots deep into the soil where the water is.” In general, Young recommends deep watering most plants once a week. For how long? It depends on your soil, but long enough to saturate the soil a good foot deep. Vegetables may need to be watered deeply two or three times a week when it is very hot, she added. Savio pushes 5-gallon planting containers (the type with drainage holes) between the plants in his garden, then fills them three times with water, once a week, to send water deep into the soil.
When you know a heat wave is approaching, you can prepare by watering abundantly low to the ground, ideally at night or very early in the morning when the air is cooler.
2. But do not over water
When temperatures hit triple digits, plants simply shut down, which means they can’t absorb or “sweat” water, said Savio. At the end of the day, the plants may appear to wither, but test the soil before removing the hose. If the soil is dry, definitely add water, which the plants can absorb once the temperatures drop at night. But if a pot is heavy or if the soil is moist about an inch below the ground, your plant doesn’t need more moisture and could actually drown from too much water. she declared. The best test is to check the plant again in the morning, Savio said. If it hasn’t recovered and is still withering, give it more water.
3. Check the jars twice a day
When it is very hot, it is essential to check the humidity of your potted plants every day, in the morning, using either a moisture meter (like this one $ 13 model on Amazon) or by digging your index finger a few inches into the soil, to see if it comes out dry (if there is wet soil clinging to your finger, the plant is not yet ready to water.) start again in the late afternoon, especially with thirsty vegetables like tomatoes, as plants in containers dry out faster than plants in the ground, so you may need to water them twice a day. Water slowly and abundantly, so that you water all the soil in the pot and don’t just send water running down the sides and bottom of the container.
4. Think about your containers
Avoid dark-colored containers, which absorb heat more than lighter colors and can actually fry a plant’s roots, Young said. Try wrapping dark pots in light-colored cloths to reduce their heat absorption. Or put potted plants in larger pots to give them some insulation and shade, but make sure both the pots have good drainage. Plants drown in standing water, even when it is hot.
5. Do not water in the sun
As tempting as it may sound, don’t water your plants in the middle of the day; these water droplets turn into mini magnifying glasses on the leaves and intensify the heat. Savio recommends spraying the plants to cool them, but only after the sun sets. (This only applies when the nights stay warm. Night watering in cooler temperatures can promote mold, so it is best to water early in the morning so that the plant has a chance to dry out during the day. .)
6. Make some shade
A large parasol works, as do airy shade cloths (30% to 40%). You can also use old sheets, fake cheesecloth, or wedged cardboard to give your plants a break from the scorching rays, especially in the afternoon when the temperatures are at their hottest. The key is to make sure your shade allows air to circulate freely around the plants. If the only rags you have on hand are dark in color, remember that they can absorb heat and burn any foliage they touch, so keep them several inches above or out of the way. Plant. Savio has some tips for shade the plants on her website. And here are a few more shade ideas, including an easy-to-make garden shade you can make using PVC pipe and a bed sheet.
7. No need to plant anymore
Plants don’t like change; even moving them from one container to another can tax them. But transplanting when the temperatures are in triple digits is just plain sadistic. Your plants will be stressed enough just trying to get through the hot weather without the added burden of trying to adjust to a new environment, Savio said. It’s best to keep them in a shady place and wait for temperatures to stay below 85 degrees for a while before transplanting them to another pot or to the ground.
8. Do not remove damaged foliage
These brown leaves and branches serve as protection against further damage and could actually house living tissue, so avoid pruning shears, at least for now.
9. Stop any pruning until fall
Even plants that look good are going to be stressed by this heat, and pruning only adds to it. Let them grow as they please and prune them when it is cooler.
10. Forget the fertilizer
Root systems suffer from high heat; absorption of fertilizer can cause further damage. Compost mulch and low-nitrogen organic fertilizers (number less than 3) are okay, Young said, if they don’t contain manure, fish, or blood because they contain salts, which can cause heat stress and burns.
11. Be ruthless
If you find that your carefully cared for young tomatoes, peppers, squash, and beans have blistered and dried out, just let them go. They won’t miraculously ripen on the vine, Savio said. Remove them so that the mom plants can focus on recovering. And be aware that high heat prevents tomato production, so don’t expect more fruit to form until temperatures drop below 85-90 degrees for 10 consecutive days.
12. Make an exception for roses
The no pruning rule does not apply to roses because they are very susceptible to disease. “You don’t want to leave a ton of tissue dead for disease and bugs,” Young said, so remove the flowers and withered branches.