When it’s hot and sunny, I try to fall back on the guidelines for container plants in stressful circumstances, clustering them together to form a microclimate, and frequently misting with a fine hose nozzle to temporarily cool foliage. I sometimes cut back stems to ease stress on root systems unable to adequately service limp leaves.
What also makes a difference is mulching the soil surface in each container. No matter if it’s a field of roses or a pot of begonias, covering the soil with organic mulch is the first and best defense against heat and drought. I often use leaves, pine needles and shredded bark to create a two- to three-inch (5- to 8-cm) layer of mulch around the stems in each pot, being sure to extend the materials all the way to the pot rims, and leaving no cracks where sunlight can enter. I learned that the depth of mulch is key to really keeping soil temperature cool, or at least cooler than it might be when fully exposed. A thin mulch (one inch / 2.5 cm or less) really didn’t do much, but the deeper layer resulted in cooler soil. As well, there is significantly less moisture evaporating, meaning less watering is needed.
Yes Judith there are many gardeners who are feeling like a cooling shower from the hose right now! Interesting to read about the gold hostas. I have one which I have always thought is ‘August Moon’ and the darn thing scorches up every year in just a touch of spring sunshine and then is devoured by slugs. I shall try to find some of the thicker ribbed-leaf ones you suggest. Thanks as usual for the always interesting articles.