Autumn is the time to consider succulents and winter protection. Caring for your succulents over winter and preparing summer outdoor planted succulents to come back inside over winter is important if you want your succulents to survive over winter. As the weather gets cooler and wetter many succulents will start to suffer, so September is a good time to start checking how they are doing and begin thinking about moving them to a better site (if in pots) or lifting plants which have been planted out in garden beds or rockeries over summer.
The majority of succulents available in the UK are not hardy enough to survive over winter without some damage. Some Sedums are winter hardy and can survive very low temperatures. Many rockery Sedums die back underground in winter and re-grow in the spring. Most Sempervivums are winter hardy if grown in a well drained and sheltered site and again can survive in very low temperatures, but cobweb Sempervivums are more easily damaged by wet weather.
Other succulents such as Echeveria, Aloe, Agave and most other succulents will need some protection from the worst of the winter weather. Some succulents can survive frost and ice if they are planted in a sheltered, well drained site (for example in dry gritty soil, and against a building on a sunny south-facing slope).
The one thing that most succulents will not tolerate is being wet for an extended period of time. Constant wet and rain will cause roots and leaves to rot. If the plant freezes when very wet it is likely that the plant will be killed. As freezing water expands in the leaves and roots, it will cause them to rupture and the plant will most likely die. So if you do keep any succulents outside over winter the most important thing to do is keep them as dry as possible.
My frosty Echeveria (pictured above) did spend a couple of winters outside on a rockery. I made small plastic shelters (plastic sheet on sticks) to go over the plants and reduce the water falling directly on the plants. However after a really bad winter with weeks of ice and frost I finally went out and dug the plants up and brought them inside in the middle of winter. Most did survive (I had a few Echeverias and a few Agaves growing outside) but they all lost quite a few leaves.
Succulents and winter – preparing your succulent plants for winter
The safest way to prepare a plant to bring it inside is firstly to thoroughly check the plant for signs of damage or insect infestation, remove any damaged or dead leaves, then clean the compost/potting medium from the roots and re-pot in fresh compost/grit. After that you should monitor the plant for signs of pests.
I have given many of my plants a soap spray to help reduce the chance of hiding insects, or as a first attempt to eliminate a suspected bug problem.
Dealing with pests and insects
There is a risk that plants which have been kept outside will have pests and when those plants are brought inside to the warmer conditions of a greenhouse or into the home, and away from normal predators, those pests may get out of control and potentially infest other plants.
- Thoroughly check the plants before bringing them inside (use a powerful magnifying lens to look between the leaves and stems).
- Quarantine your plants away from other plants already inside.
- Keep a close eye on them and make regular checks for a few weeks.
Treating plants to remove insect pests
You may need to treat the plants to kill any insects. Soapy water can be effective against many of leaf biting insects, but it may not be enough to control a serious infestation. Alcohol is used to treat mealy bugs and can be effective against other leaf biting insects. However if these don’t work or you have a persistent bug (such as thrips) then you may need to use a commercially available pesticide (after checking it is safe to use on succulents) which may need repeated treatments to be fully effective. A systemic pesticide can stay in the plant for some weeks and can kill later generations of insects which may hatch and feed on the plant some time after spraying.
2020 has been a good year for plant eating insects, so you may need to be extra vigilent.
Overwinter succulents in a greenhouse
As long as the roof doesn’t leak and the greenhouse is reasonably dry, keeping your succulent plants in a greenhouse is a possibility, especially for succulents which are usually happy outside in the warmer months. Keep them mostly dry with only very occasional watering.
Overwinter succulents in the home, conservatory or porch
You may want to bring succulent plants into the home over winter. A suitable site for them is a bright conservatory or sunroom, or on a bright sunny windowsill. Most succulents will not want to be on a north-facing windowsill (although a few such as Sanseveria and forest cacti will be happy there).
It can be difficult for sun-loving succulents to get enough light if placed on a windowsill. Their colours are likely to fade over winter. They may create weak and thin growth if watered too much in limited light conditions. Water only occasionally, when the plant needs it.