There are two completely different types of cacti. Most people think of cacti as all growing in desert or semi-desert conditions, though in fact they live in a diverse range of environments. The first and main type may grow in deserts but also in areas of scrubland with small shrubs and grass. However some cacti grow in the very different environment of forests in more shaded positions amongst and in trees in the sub-tropical and tropical rainforests of North, Central and South America, including the Caribbean islands. They are called ‘epiphytes’, which means plants that grow on the surface of other plants but are not parasites.
Epiphytes obtain moisture from rainfall and runoff from their support. Some grow in the forks of trees amongst leaf debris and bird droppings, or hang down from the upper branches of trees having anchored themselves to the stems, where pockets of decaying leaves sustain them. Others scramble upwards towards the light, clinging onto trees by long thin intertwining stems and aerial roots. They grow together with the bromeliads and orchids and make a sensational display during their flowering season. Because of their habitat they all require partial shade and compost with added humus, though still able to drain quickly and not stay sodden. The majority of them make good hanging basket subjects, especially if clumped together.
If temperatures are maintained above 10°C (50°F), which is the recommended minimum, they can be watered all year round. They do not respond well to dry, centrally-heated areas, particularly close to radiators, and a cool frost-proof room is ideal. If they are in a centrally-heated room, site them as far from radiators or other heat sources as possible or provide a microclimate, for example by placing them in a water-tray or bowl with pebbles where the pot is raised above the water level by the pebbles so that there is moisture around the plant without the pot being sat in water.
Most people recognise best the flattened stems of Schlumbergera, the Christmas and Easter cacti (Fig. 1) that are easily obtained from stores and garden centres. There are many other cultivars that flower at various other times of the year and they are all in a variety of colours and need cool conditions to encourage bud development. However when buds are forming, do not move your plants or bud drop may occur. You can move them once the flowers begin to open.
Another group comprises the genus Epiphyllum and its hybrids with other genera known as epicacti, consisting of the orchid cacti that are some of the most spectacular flowerers. They have large blooms that are often scented and there are hundreds of epicacti available. They include much of the colour spectrum from white, through cream to yellow, pink, red and purple, with many having more than one colour (Figs. 2a–f). If you sow your own seed, beware of unwanted crosses. Use a small paint brush to transfer pollen to control crosses.
There are other species that have thin trailing stems, with spine clusters, and look like a normal cactus, for example Aporocactus (the rat’s tail cactus, easy to grow and spectacular in a hanging basket) (Fig. 3) and Selenicereus (the queen of the night) (Fig. 4). This plant likes to climb and scramble along the rafters of a greenhouse, but be careful as it can push through vents. The flowers are produced throughout the summer and take several weeks to develop. The flowers begin to open around 8.00pm and are finished by 8.00am the next day, but it is worth staying up to see them. Around 230mm (9”) diameter, they form creamy-white trumpets with brownish thin outer petals and are slightly scented.
A third interesting genus is Rhipsalis with a profusion of, mainly, small flowers and colourful berries (Figs. 5a–c).
It is a good idea to give all epiphytes a spell outside during the frost-free months of the summer. Hanging baskets can be hung under trees, where the dappled shade is ideal. Pots of epicacti like a shady wall, and will often set fruit. Suitable composts include any rich in humus or peat, preferably slightly acidic and with very good drainage by the liberal addition of grit, gravel and/or sharp sand. They often have quite small root systems, particularly schlumbergeras, so when repotting, choose a pot only a little larger than their current one. As for other cacti, leave dry for a week after repotting, and longer if there is any root damage or rot. Ideally do not repot when there are buds or flowers.
Sources of supply plants can be obtained from specialist nurseries, florists, supermarkets and garden centres. From these sources, the range may be limited, but they usually offer easy-to-grow species. Preferably though, head for a cactus nursery (see CactusWorld or here for further details), or your local BCSS branch or cactus & succulent show where you can pick up special and well grown plants plus a wealth of information. Many cacti are also easy to raise from seed, and the Seed Raising page gives details of how to do this and where to obtain seeds.
A full set of cultivation leaflets are given free to new members and are available for sale in our shop.
Images: Alasdair Glen (1a, 1b, 1d), Roy Mottram (1c, 2a, 2c, 2d, 3, 4, 5a-c), Phil Crewe (2b), George Davis (2e) and Roland Tebbenham (2f)