Some yucca species can withstand high-heat, freezing temperatures and even wildfire. According to SFGate, yucca does best in full sun and well-drained soils. There are varieties and species suited to every soil type, and therefore, every Bay Area garden!
Above 104°F, many plants will survive but will show different signs of heat stress depending on plant type, maturity of the plant and factors that often come with high temperatures, such as drought or wind. Extreme air and soil temperatures slow down chemical activity and growth in plants.
From my experience, ZZ plant, spider plant or peace lilly proved to be quite heat and even direct sun tolerant, a dracaena as well, at the same time these plants grow well in indirect light conditions. Laurel or lemons are ok with heat, but surely need a lot of light. Hibiscus, tradescantia are also heat tolerant.
The general answer is around 90 degrees F, with some exceptions to the rule. This means that when temps rise above 90 and remain there for a lengthy spell: Leaves wilt. Water evaporates into the atmosphere more quickly in high heat, draining a plant's reserves.
In times of extreme heat, 1-2 times each week may be necessary. Know your plants though! Some plants prefer almost zero water during summer (manzanita, Ceanothus, madrone and cistus) and others wilt even when they have ample water (hydrangea, rhododendron). So adjust watering accordingly.
For most species, actively growing tissue is damaged by brief exposure to temperatures above 45oC, while prolonged exposure can result in fatal injury. Temperatures between 30-40oC can be termed moderately high temperatures and result in reversible inhibition of metabolism (moderate heat stress).
Cucumbers love full sun and thrive in hot summer weather. Their ideal growing temperature is between 50 and 95 degrees Fahrenheit. If it gets particularly hot, mulching is key, along with maintaining consistent moisture, allowing no more than two inches of dry soil at the surface.
Different species can tolerate different temperature extremes, but, in general, once air temperatures rise above 90°F, most plants will start to experience heat-related stress.
Eggplant Tops the List of the Best Plants for Hot Weather. Eggplants are one of the easiest fruits to grow in the garden, even in hot climates. They're related to tomatoes (they both come from the Solanaceae family), but they're way more tolerant of heat than their cousins.
Plants such as the Desert Willow, Agave, Sagebrush, and various cacti species are well-suited to desert conditions and will require less maintenance and water. Succulents are another good choice for hot, dry climates due to their ability to store water and withstand prolonged drought.
It is so hot out there!
Most plants shut down during extreme heat, so if it is over 100 degrees, it may be best to wait to water even if your plant is stressed. Throw a damp sheet over it, or mist it lightly to bring the temperature down. Mist leaves with a spray nozzle to cool down plant and reduce transpiration.
Don't Water at Mid-Day in the Sun. "Don't Water Your Plants in the Middle of the Day!" How many times have you heard that? "Only water your plants in the early mornings or late evenings." THE CHALLENGE: That's easy to say, but not always easy to do.
What time of day should you water your lawn during extreme sun and heat? “Irrigate early in the morning whenever possible,” Goatley said. “Irrigating during the heat of the day is considered to be very inefficient as evaporation rates are typically highest during this time of day.
Even if the air is hot your plants will be happier without the hot sun frying them to a crisp. Plant early in the morning or at night just before or after the sun comes up. The air tends to be cooler and the sun less intense. Whatever you do, avoid the midday sun, which is the hottest and highest in the sky.
Plastic pots are ideal for retaining moisture and do well for tropical plants. Clay and unglazed ceramic pots dry out faster but provide air exchange through the sides of the pot and work well for succulents and cacti.
The time needed to recover from stress is proportional to the severity of the damage. Plant heat stress recovery may take months for crops that have been ignored for too long during a heatwave; in extreme cases, it may be impossible to bring them back to life.
Sunstar pentas boast extra-large flower clusters - some nearly the size of hydrangea blooms - atop well-branched plants. They have excellent summer durability, blooming well through high heat and humidity, and they make ideal bedding and container plants for hot climates.