- Author: Ann Edahl
First, take care of yourself.
Especially when there is an excessive heat warning, plan any outside chores for the morning, when the temperatures are cooler.
Follow these other steps to prevent heat illness:
- Drink plenty of fluids, such as water and sports drinks. During hot weather, plan to have at least one quart of water available per person per hour of the outdoor activity. Avoid caffeinated drinks.
- Limit your time outdoors.
- Work in the shade when possible.
- Wear a summer hat with a brim and loose-fitting, light-colored, and lightweight clothing like cotton.
- Wear sunscreen (follow this tip whenever you're out in the sun).
- Schedule vigorous activities during the coolest portions of the day and take frequent breaks on hot days.
- If you are feeling symptoms of heat illness, take a rest period in a shaded area. Monitor others around you for symptoms as well.
- Do not overdo! Your weeds will still be there when it cools down a bit.
Next, take care of your plants.
During heat waves, our number-one gardening goal is to keep our plants alive. Plants are sensitive to soil temperature and air temperature, and both can stress them out. You will often see slowing of plant growth or even dropping of flowers during heat waves. For example, many vegetable plants stop flowering above about 90 degrees. Not all is lost, though. If you can get them through the heat wave, they should start producing again when the temps go down.
Plants cool themselves through evaporation, through the pores on their leaves. Generally speaking, the higher the temperature, the greater the water loss. One sign of this is drooping and wilted leaves. In addition, excessive exposure to sunlight can cause sunburn on leaves and stems. Sunburned leaves will be discolored and may turn brown and crispy around the edges. Plants that are highly stressed can also become more vulnerable to insect damage.
Our goal is to minimize the stress brought on by the heat and to avoid doing anything that will stress our plants even more. Here are some dos and don'ts to help mitigate damage to your plants during a heat wave.
DO
- Water your plants thoroughly in the morning if extreme heat is expected. This will help plants cope with the heat. Plants in small pots may even need to be watered twice a day. Check the soil moisture first.
- Water trees deeply and less frequently (that's right, less). The key is “deeply.” This encourages deep roots. Frequent, short periods of watering mean that the roots remain shallow.
- Use a shade cloth (even a bed sheet can work) to shade plants from direct sun and lower the air temperature around the plant.
- Harvest ripening fruit. This can help plants conserve their energy.
- Pay close attention to newly planted plants. They may need more TLC.
- Check on plants that are right next to a walkway or patio. The radiant heat from material like pavers or concrete may cause those plants to show signs of water stress first.
- Mulch, mulch, mulch! A good layer (3 to 4 inches) of mulch, such as compost or wood chips, will prevent the soil around the plant from heating up excessively and will also reduce the amount of water loss. Make sure the mulch is not directly up against the plant, as that can encourage disease.
DON'T
- Do not water midday.
- Do not prune - this will send the plant's energy toward the wound. (Pruning dead branches, especially those that may be a hazard, is fine.)
- Do not fertilize - we don't want to encourage new growth during this period.
- Do not plant or transplant during the heat of summer. It's best to wait until fall for any new planting.
Read more:
Melissa G. Womack. Hot Weather Tips for the Summer Garden. University of California Agriculture and Natural Resources.
University of California Marin Master Gardeners. Heat: Plant Stress in High Temperatures.
- Author: Mike Hsu
Much of California is experiencing high temperatures with predictions of extended high heat through next week, so this is a good time to review heat safety information and recommendations.
Please take appropriate heat illness prevention measures throughout the holiday weekend and beyond, especially those who are working or spending time outdoors. You can find UC ANR information and resources about preventing heat illness at https://ucanr.edu/sites/ucanr/News/Heat/ and https://safety.ucanr.edu/Programs/Heat_Illness_Prevention/.
For current weather alert information, Cal/OSHA recommends the NOAA Weather Alerts page at: http://alerts.weather.gov/cap/ca.php?x=1
Cal/OSHA sent a reminder for employers to protect outdoor workers from heat illness that offers the following recommendations:
- Plan – Develop and implement an effective written heat illness prevention plan that includes emergency response procedures.
- Training – Train all employees and supervisors on heat illness prevention.
- Water – Provide drinking water that is fresh, pure, suitably cool and free of charge so that each worker can drink at least 1 quart per hour and encourage workers to do so.
- Rest – Encourage workers to take a cool-down rest in the shade for at least five minutes when they feel the need to do so to protect themselves from overheating. Workers should not wait until they feel sick to cool down.
- Shade – Provide proper shade when temperatures exceed 80 degrees. Workers have the right to request and be provided shade to cool off at any time.
- Author: Pamela Kan-Rice
September is National Preparedness Month, designated to encourage disaster and emergency readiness. To help Californians prepare for extreme heat, earthquakes, public safety power shutoffs and wildfire, University of California Cooperative Extension has created a disaster preparedness website organized for quick access to critical information.
The website https://ucanr.edu/Disaster contains fact sheets with tips for getting prepared.
“Unfortunately, with a warming climate, we are facing more and more extreme climate-related events such as heat waves, wildfires, power shutoffs and storms. All Californians need to step up their preparedness efforts to be ready to meet this more uncertain future,” said Susan Kocher, UC Cooperative Extension forestry advisor, who co-authored the disaster preparedness resources for the website.
Extreme heat
The fact sheet for extreme heat events offers suggestions for avoiding heat exposure, such as identifying nearby cooling centers and covering windows to keep heat out. It also suggests things to do during hot weather such as staying hydrated, taking cool showers and keeping pets indoors. It describes symptoms of heat-related illnesses, which can have serious health effects.
Public Safety Power Shutoff
During extreme weather events, electrical power in high fire-threat areas may be shut off to prevent sparking. This precaution is known as a Public Safety Power Shutoff. A PSPS is most likely to occur from May to November, when conditions are the hottest and driest.
UC Cooperative Extension recommends signing up to receive PSPS alerts from your energy company. Experts also advise making a plan for medications that need to be refrigerated or medical devices that require power. To prevent foodborne illness, they offer suggestions for ensuring food safety during and after a power outage.
Wildfire and smoke
Wildfire smoke can harm your health. During wildfires, UC Cooperative Extension recommends wearing an N95 outdoors to reduce smoke exposure and taking steps to prevent smoke from entering buildings. To reduce wildfire risk, the website describes methods of removing flammable vegetation around homes.
Earthquakes
UC Cooperative Extension offers safety tips for before, during and after an earthquake. Identifying the safest place in your home during an earthquake in advance is helpful. For example, doorways are not the safest place to be in modern homes. Experts recommend crawling under a sturdy desk or table, while avoiding areas next to windows, beneath ceiling fixtures or near large items that may fall during an earthquake.
The website also offers resources on drought, food safety after a fire, and wildfire preparedness and recovery.
In 2020 and 2021, Cooperative Extension researchers from around the country held listening sessions with community members who had experienced extreme weather events and other types of disasters to learn what had worked well, what had not, and how communities could be strengthened.
In response, these disaster resources were developed by Kocher, UC Davis undergraduate student Caydee Schweitzer, Tracy Schohr, UC Cooperative Extension livestock and natural resource advisor, and Vikram Koundinya, UC Cooperative Extension evaluation specialist. The group plans to add fact sheets on more disaster topics in the future.
This project was funded by a USDA National Institute of Food and Agriculture Renewable Resources Extension Act grant.
MEDIA CONTACT: Susan Kocher, UC Cooperative Extension forestry advisor, sdkocher@ucanr.edu
/h3>/h3>/h3>/h3>- Author: Jeannette E. Warnert
When unusually hot weather is in the forecast, it's time irrigate, shade and mulch plants to protect your plants, reported Sandra Barrera in the Los Angeles Daily News.
The story was prompted by a heat spike in Southern California recently, when temperatures soared above 110 degrees in many areas.
"While most plants can endure triple-digit temperatures, they suffer when heat comes on suddenly," the article said.
- When a plant is dry, it's already stressed, so give it a good soaking before temperatures rise.
- A patio umbrella, bed sheets or landscape shade cloth suspended on the sunny side of a plant will shade tender growth on hot days.
- A three- to four-inch layer of mulch around plants will cool roots and hold moisture.
One of the best ways to avoid heat damaged trees and plants is by planning a garden for the climate.
"In Southern California, Sunset zones are preferred over USDA zones due to their greater accuracy," said Janet Hartin, UC Cooperative Extension environmental horticulture advisor for San Bernardino, Riverside and Los Angeles counties.
The American Horticultural Society also has a Heat Zone Map to select plants adaptable to inland and desert climates. The map has 12 zones searchable by city. Each zone designates the average number of days per year temperatures exceed 86 degrees, which is considered by the point at which most plants begin to suffer heat stress.
"The numbers are relatively conservative and many plant enthusiast experimenters are already finding that many plants - under the right conditions and a little shade - do just fine outside of their listed heat zone," Hartin said.
- Author: Ben Faber
So, this weekend we had some hot weather and the damage from that heat is apparent in all kinds of plants. Sycamores, cottonwoods and willow in the Santa Clara River bottom look torched. Redwoods in the landscape look like a new disease has hit them.
Even old coast live oak in Ojai have been toasted. Orchards have been hit also with been hit without exception. This has been a widespread weather phenomenon like a major freeze. And the trees should be treated as if they have been freeze damaged.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=12275
So, what to do with the avocados and citrus that have been hit? Well, if it's just a slight toasting, nothing. They will grow out of it. It's a setback. The growing points, the terminal buds, have been damaged and in the case of avocados those may not flower next spring. If the damage is not extensive, the whole canopy has not been damaged, then flowering should be sufficient for a good crop next year. If the whole canopy has been hit, it's likely that flowering will be minimal next year.
If the trees have lost significant portions of the canopy, though, the heat damage is not the problem, it's the sunburn damage that is going to happen that is the problem. It's the loss of the leaves that transpire and cool the tree that lead to this kind of damage that can kill small trees and lead to significant branch loss in older trees.
The leaves act like the radiator in a car. They move water through the tree and that water movement carries off the heat that accumulates in the branches and stems. When water flow stops, the bark heats up and tissue is damaged. The worst-case scenario occurs when a “renovated” tree that has been brought down to 6 feet in January and since then there has been new growth all over the tree. The heat fries that new growth and now the whole tree structure is exposed to sunburn damage.
The branches exposed to the sun need to be protected with whitewash. The whitewash needs to be WHITE, not grey. It needs to be able to reflect the sun and prevent the surface from heating. The tops of branches and the west and south sides need to be the most protected, so it often involved hand work. And it needs to be done soon after the canopy loss. That wood heats up fast and damage occurs soon after it heats up.
So what else needs to be done? No canopy, no water loss, so it's necessary to manage the water differently. With no leaves, there is no water moving from soil through the tree, so it just sits there, and the ground stays wet. Perfect conditions for root rot.
Growers who were watering their trees knowing that a heat spell was coming, did the right thing. It probably reduced the severity of the damage, but even growers who had water on before the heat and it was running during the heat have had damage. With canopy damage and loss, applied water needs to be restricted to just enough to get tree recovery without creating a wet, soggy condition. And with tree recovery, it's going to need a continually changing irrigation schedule as new growth occurs.
So now more than ever, water to the tree's growing needs. And the normal fertilizer program needs to be adjusted. There's probably sufficient nutrients in the soil from prior fertilization that nothing new needs to be applied.
And don't' prune the trees. Leave the hanging leaves there. They will help protect the tree from sunburn, but the extent of the damage is not clear. Let the tree push new growth and that will tell you sometime in the future 3-6 months, even a year from this event, when to do significant pruning.
Phlood, Phyre, Phrost, Fytophthora and Phahrenheit continue to plague our industry. It seems like we are always coping with some natural and some unnatural issues affecting agriculture. Oh, yeah and pH.
Photo: Heat singed new avocado growth.