The common linking characteristic of cacti and succulents is the ability to store water in the leaves or stems enabling them to survive in arid habitats. All cacti are succulents, yet cacti are defined by the presence of areoles (specialised sites where spines form) whereas succulents have none.
The majority of cacti and succulents grow in desert and savannah situations with low moisture, dry air, bright sunshine, good drainage and high temperatures. However there are succulents such as Schlumbergera and Epiphyllum which grow as epiphytes in rainforests. These require semi-shade and humid conditions. So to cultivate cacti and succulents successfully it is best to research their native habitat, to provide their ideal growing conditions as far as possible.
Cacti and succulents utilise the Crassulacean acid metabolism (CAM) photosynthetic pathway. Although this makes the best use water, it is much less efficient than other photosynthetic pathways, hence the slow growth of cacti and succulents compared to other plants.
How to care for cacti and succulents typically grown as houseplants
Compost
The compost must be open and free draining, to help prevent waterlogging and recreate natural habitat. Cacti compost is readily available from garden centres. Alternatively, use John Innes No 2 with up to 30 percent extra grit or fine gravel by volume, to help with drainage.
Re-pot pot-bound plants in spring, into a pot only slightly larger in diameter.
Holding spiny specimens can be tricky when re-potting so use thick strips of folded newspaper as tongs or an oven glove.
Position
Most cacti and succulents can be placed on a sunny or bright window all year round. Forest-growing epiphytes such as Rhipsalis, however, need semi-shade.
During the winter it is beneficial for plants to have cool night temperatures of 8-10°C (46-50°F) as a minimum, for a period of rest.
Central heating is not usually a problem for these plants over the winter; just remember they need sufficient water to prevent them from shrivelling.
Watering, feeding and ventilation
Spring and summer
- From April onwards water cacti and succulents freely, allowing excess water to drain away
- The compost should be allowed to dry out slightly between waterings, rather than keeping it constantly moist
- Forest-growing epiphytes will benefit from a humid atmosphere
- Feed established plants once a month during the growing season (April-September) using either a liquid houseplant feed or specialist liquid cacti feed
- Cacti and succulents need fresh air and particularly need good ventilation during the summer months
Autumn and winter
- From about September onwards reduce watering to a minimum, to encourage a period of rest
- Allow the compost to virtually dry out before watering
- Some desert dwellers can be left un-watered from early November to the end of February especially if they are away from overly heated rooms
- Winter-flowering types will require warmth and regular watering during this time, to be then followed with a resting period in summer
Ideally use tepid rainwater for watering. The minerals in tap water builds up in the soil and can cause deposits on the leaves of succulents.
Flowering
Cacti and succulents will perform and look better if you allow them to follow their natural seasonal pattern. A period of rest, to mimic the dry season, to be then followed by an increase in water to act as the rainy season will ensure a good display of flowers. Always check as to what seasonal treatment is required as some will need to rest in the winter to then flower in the spring, while others will rest over summer to flower in the autumn.