Don't let harsh sun and high heat harm your succulents! Heat, unlike frost (temps 32 degrees F and lower), usually isn't a concern for succulents. Although some tend not to thrive in temps above 80 or 90 degrees F, the majority can handle more than you're personally comfortable with...as evidenced by greenhouse temperatures that soar into the triple digits on summer days. However, heat plus sun can be deadly to succulents. Unless they're desert cacti or agaves, most smooth-leaved succulents need sun protection in summer, especially above 80 degrees.
If you live in an arid climate ~
- Know your property's orientation to the sun. In North America, plants growing on your home's north side will get the least amount of sun exposure; those on the south, the most. East-facing gardens like mine get morning sun and afternoon shade. Gardens facing west have afternoon sun and morning shade.
- "Bright shade" (no direct sun but not deep shade) is ideal for non-desert succulents in mid-afternoon when temperatures peak. Bright shade is essential for low-light succulents such as haworthias, gasterias, euphorbias, faucarias, sansevierias, sempervivums, and anything light-colored or variegated. (There are exceptions; for the requirements of specific plants, see the "Succulents A to Z" chapter of Designing with Succulents.)
- Whenever you buy a new plant, notice where it was located in the nursery. Was it out in the open or beneath shade cloth? Even if it's a "full sun" succulent---like an agave---if it was growing in a sheltered area, it'll need to be "hardened off" (shaded, especially in the afternoon) until it acclimates. Such exposure is similar to tanning: Start with 30 min. of sun and increase it by an hour or so each day.
- Give aloes and crassulas enough sun to turn hues of red and orange but not so much that leaf tips shrivel or burn---at least half a day. (See "How to Stress Succulents and Why You Should.")
- Because sunburned stems are less able to transmit moisture from roots to leaves, be sure to cover exposed, horizontal stems of trailing succulents (aloes, senecios, othonna and the like) with dry leaves or mulch.
- Protect newly installed plants and in-ground succulents susceptible to sun-scorch with floating row covers (ideally), shade cloth, old sheets or temporary shade structures. I use old window screens. In a pinch, set leafy tree trimmings upright in the ground next to a plant you want to protect, on the side that gets the most sun. Or use outdoor furniture, keeping in mind the sun moves throughout the day.
- Understand how plants protect themselves. Succulents can't scurry off to shade when sun is intolerable, so some provide their own. Rosette succulents such as dudleyas, aeoniums and certain aloes will close their rosettes to protect their vital cores. Lower leaves that dry but don't fall off have a purpose: They shade vulnerable stems in summer and insulate them from cold in winter.
- Plant trees and shrubs that'll provide shade where needed during long, hot summer afternoons. (For low-water varieties good in succulent gardens, see the Companion Plants chapter of Designing with Succulents, 2nd ed.).
What sunburn looks like
White, beige or black patches on succulents indicate sunburn, meaning cells have been irrevocably damaged---an effect similar to frost. Although the plant is fine, scars will last as long as the leaf does.
If marred areas are on outer leaves, so much the better; new growth from the center of the rosette will conceal sunburned areas over time. In any case, lower leaves---damaged or not---naturally wither and fall off. Depending on the succulent and the season, recovery from sunburn may take several months to a year.
How to Water Succulents in Summer. OK, we all know that succulents are low-water plants. But they’re not “no-water” plants. Although they may survive without irrigation during the heat of summer... [continue reading]
Don't Let a Heat Wave Ruin Your Succulents. When a heat wave follows cool weather, succulents exposed to hot sun may burn. There's no fixing the beige or brown patches that result from sunburn. [continue reading]
Succulents, Sun and Summer. On an 89-degree day in my garden, I show you what's in bloom and lookin' good (or sadly dreadful), and explain how to evaluate the health of your in-ground succulents, small and large.
Twelve Low-Water Trees for Succulent Landscapes. I help you evaluate garden areas in need of shade and select trees to plant when the weather cools in the fall.