Don’t Let a Heat Wave Ruin Your Succulents

Sunburn concerns

When a heat wave follows cool weather, succulents exposed to hot sun may burn. Unfortunately here's no fixing the beige or brown patches that result from sunburn. One of the best things about succulents is also the worst: they keep their leaves for a long time. Damage may be visible for quite a while.

I propped a window screen against this west-facing window box to help a newly planted echeveria acclimate to greater sun exposure. I removed the screen a week later during a convenient stretch of cloudy weather.

Variegates tend to scorch more easily due to less protective pigment.

How to protect your plants

1. Move them. Of course this is only possible if they're in pots. But don't forget to do it! Move plants out of harsh midday sun and provide more shady hours daily.
2. Cover them. This is advisable for delicate, thin-leaved, in-ground succulents---in particular those you prize---and anything newly planted. Protect echeverias, kalanchoes, dainty sedums, sansevierias, sempervivums, caudiciforms, and chubby and Medusa euphorbias (among others). Use floating row cover ideally; or shade cloth, old sheets or screens. Remove as temps return to normal.

It may surprise you that the only succulent in the photo likely to sunburn is the furcraea at upper right. Its thin, variegated leaves are highly susceptible. The others---such as lampranthus ice plant, Aloe cameronii, blue senecio and firesticks---are generally not at risk except in desert climates.

How to Water Succulents in Summer

• Water early in the morning or late in the day. Watering in midday heat can literally cook roots with hot water, especially in desert climates. See my favorite hoses. 
• A hose lying in summer sun can contain scalding water. You already know this, but your house-sitter may not, so be sure to mention it. If you have a hose-full of hot water, aim a fine spray skyward. Droplets will cool by the time they hit leaves.

Aeoniums in summer. Closed rosettes indicate dormancy. See: Should You Water Aeoniums in Summer?

• What about aeoniums? If they're not entirely dormant (they're lush and green), it's OK to water them. However, like dudleyas, if they've closed their rosettes, they've gone dormant and watering them could cause roots to rot. They'll revive during winter rains.
• Trees and shrubs want water where their canopies would naturally direct rainfall: around the perimeter of the plant.
• Add gravel topdressing (or organic mulch for woody plants) to help hold moisture in the soil.
• If the ground is concrete-hard, leave a hose dripping overnight to create an underground cone of moist soil.
• When hose-watering, take the opportunity to blast pests, fallen leaves and dirt out of leaf axils and the centers of rosettes.
• Use a hose-end nozzle—ideally one with multiple settings—to direct water where you want it.

What about potted succulents?

Aim to keep soil about as moist as a wrung-out sponge. Once or twice a week should do it, depending on temperature and humidity. Water thoroughly to soak the soil and flush salts.

High-heat succulents

A colorful Arizona garden

Succulents that can handle triple-digits without extra water (but look better with it) include cacti, jade-like crassulas, elephant's food, large aloes and agaves, beaucarneas, hesperaloes, and yuccas.

In habitat, cacti will lose delicate roots essential for taking up water when the soil goes completely dry. They live on stored moisture, then regenerate roots when the rains return.