A heat wave is like a brushfire. If it gets too intense, there is really not much you can do to blunt its force. Once a brushfire turns into a wildfire or major conflagration, all the prudent firescaping measures in the world will not help. If you seriously want to avoid the possibility of property loss due to a raging wildfire, you will simply have to relocate to more urban surroundings. And if you desire to tend a garden immune to heat damage, you will need to move to Scandinavia.
There is probably only one measure that could have saved your plants from the recent sizzling heat wave and that would have been an overhead misting system. When 100+ degree weather is forecast, deep watering and mulching to minimize evaporation from the soil surface are wise measures to prevent heat stress. However, there is no defense against the 115 degree heat we recently experienced except misting.
There is a widespread misconception that getting leaves wet in the heat of the day can harm your plants. “Water droplets act as tiny magnifying glasses, focusing the sun’s rays so that your plants get scorched” is accepted wisdom among a large proportion of the gardening public, but nothing could be further from the truth.
In Australia, in order to prevent scorched fruit on a 40 acre ‘Granny Smith’ apple orchard, an overhead misting system was installed. Sunburn loss was reduced from 10% to 2% of the apple crop. Misting systems, which are especially effective at cooling off hot patio and balcony planters, are readily available through online vendors.
You do not have to go to Australia to be convinced that overhead wetting of leaves does not damage plants. Of the 55 million acres of irrigated agriculture in the United States, 28 million acres are watered by overhead sprinklers on a center pivot system that slowly circles through a field for as long as 24 consecutive hours at a time. Among crops that receive overhead irrigation in the heat of the day are alfalfa, wheat, corn, soybeans, cotton, sugar cane, sugar beets, and watermelon.
“I am a 96 year old who has collected plants for years. Ten years ago I got a small plant that the seller said was elephant food. It takes little care or water and now is about eight feet tall. It blooms every summer and is covered with pink blossoms.”
Don Peyer, Carson
elephant food (Portulacaria afra), photo by Don Peyer
In the wake of those recent scorching days, Peyer sent me a photo his elephant food (Portulacaria afra) specimen. Other than a bougainvillea or a crepe myrtle, I have never seen such a large plant covered head to toe with flowers in July. There is something special about Peyer’s particular plant or growing conditions since elephant food, which serves as a favorite snack of elephants and other grazing animals in the African veld, has a reputation for seldom, if ever, flowering under garden conditions, yet Peyer’s has been flowering for three straight years. The recommendation commonly advanced to coax elephant food into flowering is to deprive it of any irrigation once it has reached a height of six feet.
Creeping myoporum (Myoporum parvifolium) is an Australian groundcover highly recommended for scorching weather. Once established, it should not be watered more than once a month. Its early demise is invariably associated with over watering. This is a plant that hugs the earth and roots wherever its stems touch the ground. A single plant will enlarge to a diameter of nine feet. It blooms in white throughout spring and summer and is eminently suitable for spilling out of a planter or cascading down a block wall.
Tip of the Week: Angel Pelargoniums are a serious option for every flower box and sun-splashed sidewalk planter. They are the result of hybridization between regal or Martha Washington geranium (Pelargonium x domesticum) and lemon-scented geranium (Pelargonium crispum). The flowers come in all the wonderful colors of Martha Washingtons except they are only an inch across. Leaves are sharply serrated and a strong lemon fragrance emerges from them when crushed. Unfortunately, you hardly ever see Angels. I did find the ‘Veronica Contreras’ variety at anniesannuals.com, a phenomenal website and nursery. You can easily spend an hour on this website without noticing the passage of time due to the wealth of rarely seen botanical gems that are pictured and described.