Temperatures round the world are getting more erratic and records seem to be dropping yearly. Recently Canada, of all places, experienced 49.5C/121F. I know very well how these kinds of temperatures feel as our small nursery is based west of Sydney in Australia where in summer it can easily get to mid 40’s. I have also seen first hand what a devastating effect heatwaves of this magnitude have on succulents (and other plants), not to mention wildlife. However, there are ways to protect succulents from burning or boiling to death in the scorching sun and they are surprisingly easy.
How hot is it in the sun vs shade
It is important to remember that weather forecast temperatures are for shade, not full sun. The temperature in the sun is a lot higher (you can do an experiment and place a thermometer in full sun to see).
So plants exposed to full sun, if its say 40C/104F is likely to be some 10C higher depending on other factors like how much shade cover is nearby and what the colour of the surrounding environment is.
How to protect succulents in pots in a heatwave
Succulents in pots are very vulnerable as pots can heat up to high temperatures, well above the forecast numbers. On very hot days they can even be too hot to touch! To protect succulents from suffering burns/ completely drying out or heating to a point of collapsing, simply place the pots in shade/ create shade by erecting an umbrella above or pitch a shade-cloth over.
It will also help immensely if the pots are not black or dark colour as they heat up much more than light coloured pots. Having said that, even light coloured pots heat up if in direct sun on a very hot day.
When putting up a shade shelter for succulents the movement of the sun should be anticipated. As the sun moves throughout the day it can shine into the shelter, especially later in the day. Making sides will help. Same can be said for moving potted succulents into shade- if the sun moves beyond the shade, a plant can completely burn in less than 30 minutes of exposure to sun's rays on a day over 40C/104F.
Placing succulents under a tree or in a shaded spot for the duration of summer if heatwaves are predicted is a good solution. It will need to be a bright shade outdoors, so the succulents do not loose their look and get too leggy.
Succulents do not mind the heat and should easily survive in shade temperatures over 50C/122F. It is the sun’s rays and UV that cause burns and death. It is quite similar with humans too- although we struggle in the heat, if we’re in shade we would likely survive the day, but in full sun our skin would burn and the heat could kill us.
How to protect succulents in the ground in the heatwave
It is harder to move succulents planted in the garden and so they will have to be protected by pitching a shelter above. An umbrella, shade-cloth or even a sheet/ peace of cloth can put over to get plants over the worst of the heatwave. Whatever material is used, it shouldn’t touch the plants.
I have previously used anything from bamboo sticks to star posts to quickly pitch a small protective shade-cloth tent over garden plants and it works a treat. It is only when its windy, that you will need to do a little a more and secure the cloth to sticks/ post or whatever you choose to use with string, cable ties etc. or peg it down with tent pegs.
Which succulents are most susceptible to burning in a heatwave
The most susceptible succulent that can burn very fast in hot sun are young and small succulents, cuttings, succulents with small and thin leaves, succulents that prefer shade over sun and ‘touchy succulents'.
Young and small succulents that are only a fraction of their full size tend to fare worse than established, mature plants. They don’t have as much water stored away in their stems and leaves and the roots are not yet as big either. Combined, it makes young succulents prone to getting damaged or dying in a heatwave
The same applies for succulents that naturally grow small leaves on thin stems (Sedum Little Missy, Sedum Green Mound, Miniature Delosperma, thin leaf Echeveria such as Glauca etc.). These plants are just not meant to be in exposed to direct sun during extreme heatwaves and are very likely to die altogether in sun over 35C/95F.
Not all succulents are alike and some prefer bright shade over direct sun exposure. These are mainly Haworthia, Gasteria, many variegated succulents, the ‘String of’ Senecio such as String of Pearls or Bananas (Senecio Rowleyanus & Radicans)and some others. Shade lovers will burn and die at much lower temperatures when exposed to the sun, than sun lovers. As long as they are in a shade during a heatwave, they will survive though.
And then there are those touchy succulents. These are usually hybrid plants (Echeveria Romeo, Echeveria Rainbow, Echeveria Purple Pearl) that were bread selectively for their looks and are sensitive to a number of factors, heat being one of them. They are mostly a plants cross-bred in the Echeveria genus creating beautiful but often sensitive plants that will need to be shielded from direct sun during a heatwave.
Which succulents are unlikely to suffer in a heatwave
There are a number of succulents that are extremely hardy and can survive even an extreme heatwave unprotected. Some of my favourites are Crassule Ericoides, Crassula Ovata species, Graptopetalum Paraguaynse, Sedeveria Starburst, Sedum Rubrotinctum.
A lot also depends on their particular environment and where they are planted. Even the hardiest of plants will have hard time surviving if they are in a small, black pot exposed to all day sun during a heatwave.
How to heal a sunburnt succulent
Once a succulent burns the marks will not go away, but the plant can be saved. In time new growth will replace the burnt leaves, but the burns themselves cannot be healed. A sunburnt succulent should be placed in a bright shade/only early morning sun position immediately to stop any further damage from happening. The burnt leaves, depending on where they are, can be pulled off or left as they are and let the time do the healing.
After the leaves are burnt plants will just grow at their normal rate and new leaves will push the burnt leaves out of sight.
Another solution is to behead the succulent and let new growth replace the burnt part. We have a how to guide and video on beheading succulents here.
What temperature is too hot for succulents
How hot is too hot will differ from species to species, but in general once the temperatures start rising over 35C/95F most potted succulents should be protected from direct sun. Garden succulents have a slightly higher threshold of about 40C/104F, but some species may suffer even when exposed to sun at lower temperatures. In the shade, succulents should cope with heat to about 60C/140F.
As I’ve said before plants in the ground will withstand more than succulents planted in pots, but if the plant in the ground also happens to be a touchy succulent or a shade-lover exposed to extreme sun, than they may die even at temperatures lower than mentioned above.
How our nursery grows succulents during extreme heat events
Our nursery is no stranger to extreme heatwaves and we routinely have to face temperatures over 40C/104F in summer. Because we sell to the public our succulents need to look pretty and can’t have any marks. At the same time we want them to be hardy for their new homes and so most of our succulents live outdoors year round unlike the majority of plants coming from mega nurseries who tend to have state of the art greenhouses with cooling and heating systems in place. In my opinion using cozy greenhouses makes succulents a little less hardy in extreme weather scenarios and they can burn more easily than plants raised in the elements. We also use hard cover greenhouses, but they are for the sole purpose of keeping the rain out from sensitive plants that tend to rot if it rains too much.
We use 30% shade-cloth over our outdoor succulents when the weather starts heating up. Shade-cloth ensures that the harmful UV rays will not reach our succulents on hot days, but will expose them to quite a bit of sun so they stay compact, colourful and hardy. It also protects plants during hailstorms and keeps leaves and other debris out on windy days.
The shade-cloth provides enough protection to prevent burns even when over 45C/113F. During heatwaves we also water regularly, but mostly in the evening and never during the day as water droplets can intensify sun’s rays and act like glass. Some succulents are happier with lots of water but other prefer to be on the dry side, even during heatwaves. It is hard to give universal advice on every single succulent in the world but even the most sensitive succulents will enjoy a proper soak when too hot. It is important to remember that they should not be in soggy potting mix for too long and to let the potting mix dry out between waterings. During particularly hot summers most outdoor pots will dry in a day or two.
Dealing with heatwaves is not easy for any form of life on this earth, but simple solutions can go a long way in making the struggle easier. Cover over any plants can be a life saver and don’t forget to leave dishes of water around the garden for the wildlife. We find bees, other insects, birds & lizzards to be incredibly grateful for a sip.