A GENERAL GUIDE TO CULTIVATION OF CACTI AND OTHER SUCCULENT PLANTS
Most cacti and the ‘other succulents’ are easy to grow and require minimal attention. In fact they are usually easier to look after than most ‘normal’ house plants.
Many people think of them as growing in ‘Sahara-like’ conditions. This is quite untrue. Some are jungle plants (the epiphytes), although most grow in arid scrub land where they have some protection from the scorching sun.
The majority are easy to flower when mature and will continue to bloom each year, given the right conditions. A large number of the globular cacti will flower at between 3 – 5 years from seed, and many of the other succulents will flower even earlier.
Cacti belong to their own plant family, the Cactaceae, and almost without exception are indigenous to the American continent. They have one common characteristic that distinguishes them from all other plant families. This is the areole, which is a small ‘cushion’ from which flowers, spines and branches develop. In some cacti it is very pronounced (e.g. Opuntia) whilst in others it is hardly visible (e.g. Epiphyllum). Parallel evolution has occurred in other groups, particularly the Euphorbias of Africa, and it is often difficult for the new collector to distinguish between these and true cacti.
Plants that are adapted to survive in relatively dry conditions are called xerophytes. Those that achieve this by storing moisture are called succulents. Some do so in their root system, others in the leaves, but the largest group are stem succulents. It is into this last group that almost all the cacti fit. So, (with few exceptions) all cacti are succulent, but not all succulents are cacti. It is because of this water-storing ability that such plants are able to withstand long periods of drought.
SUMMER TREATMENT
All plants must have water during the summer to make them grow. Whilst all cacti and other succulents are fairly tolerant of neglect, they will succumb to rot if over-watered. The main growing period is April to September, although the plants should be coaxed into growth with light watering in mid-March and then the amount should be gradually increased. The best way of watering is to soak the pot thoroughly and then leave it until just dry and repeat Do not allow them to stand in water for long periods. Excess water should be allowed to drain through and then be discarded, as succulents do not like ‘wet feet’.
Most succulent plants will grow best in south facing aspects in full sun, providing they have good ventilation and are given adequate water, otherwise an east or west aspect may be better. Some plants, such as Epiphyllums, Christmas and Easter Cacti, Haworthias and Gasterias etc. require good light but not full sun, and do very well with a northerly aspect. Generally speaking, more sun tends to encourage flowering, but beware of scorching if there is insufficient ventilation.
WINTER TREATMENT
During the winter, most cacti are dormant and should be kept completely dry, when a minimum of 5°C (40°F) will suffice. The normal watering should be gradually reduced at the beginning of October, reducing to zero by late October. The exceptions are some of the winter growing succulents which require a little moisture and subsequently a little extra warmth.
If plants are grown indoors during the winter, the temperature is likely to be somewhat higher, but as winter growth is normally weak, only a little water should be given to avoid the plant shrivelling, rather than to make it grow. Place plants in good light, but if on a windowsill, remove them at night to prevent frost damage during very cold periods.
COMPOST
Compost may be loam or peat-based, but must contain extra grit for good drainage. A popular compost mix for many growers is 3 parts John Innes No. 2 or 3 with 1 part grit, coarse sand or Perlite. For more difficult species the proportion of grit or Perlite is increased. It is often advantageous to add a top dressing of grit, coarse sand or small pebbles to enhance the appearance and to reduce the tendency for rot at the base of the plant.
Most plants respond well to feeding at approximately monthly intervals, especially when repotting is overdue. The best fertilisers to use are those recommended for tomatoes, these being low in nitrates, and high in phosphates.
A GUIDE TO CULTIVATION OF LITHOPS
Lithops are members of the family Aizoaceae (sometimes known as Mesembryanthemaceae, or Mesembs) and come from South Africa and Namibia. They are in a group informally known as ‘stemless mesembs’ and are related to the ice plants’ commonly grown as garden annuals in the UK. They are not difficult to grow and flower providing their simple cultural requirements are met.
An individual Lithops plant consists of two thickened leaves almost completely fused together, that appear to arise directly from the top of the root The leaf top is usually flattened and covered with intricate coloured patterns, these markings being of significance to their classification. Leaf pairs grow afresh each year but the basic markings remain the same. Each leaf pair is referred to as a ‘body’, most species eventually branching with age to form a clump of several bodies. The name Lithops, although it looks like a plural word, is actually the botanical name for the genus and is used to refer to a single individual as well as a group. It is derived from the Greek and means ‘stone face’. These plants are also informally known as Living Stones or Pebble Plants.
WINTER TREATMENT
During the winter, Lithops plants should be kept completely dry, when a minimum of about 5°C (40°F) will suffice. Even if shrivelling occurs, no water should be given from about mid-November. It may even be necessary to stop watering earlier if conditions are cold and dull, although some species, e.g. Lithops optica may not yet have flowered, and could benefit from light watering even up to Christmas depending on the sun and temperature. During the dry period, each body grows a new pair of leaves, the old pair shrivelling up as the stored water is used for growing the new pair. Place plants in good light at all times, but remember if placed on a windowsill, remove them at night to prevent frost damage during very cold periods.
SUMMER TREATMENT
The main growing period is from about mid-April to October, when the new bodies emerge through the dry skins of the previous year’s growth. Water should not be given until the old skins have completely dried up, probably about the end of May. As with cacti, the best method of watering is to soak the pot thoroughly and then leave it until just dry and repeat. Do not allow these plants to stand in water for long periods. Excess water should be allowed to drain through and then be discarded. Whilst fairly tolerant of neglect, they will succumb to rot if over-watered. If in doubt, always err on the side of dryness as over-watered plants grow tall, bloated and ugly. However, if the new pair of leaves is shrivelling, then you are not providing enough water.
Pebble Plants should always be grown in good light, with adequate ventilation. Although it is possible to grow them in lower light levels, the growth tends to be rather elongated, and flowers unlikely. Greenhouse conditions are ideal, and flowers, usually yellow or white can then be expected every year between July and October, depending on the species. The flower emerges from between the two leaves at the fissure, and is often sweetly almond-scented. Fruits will sometimes form, especially if flowers from different individuals of the same species are tickled with a paintbrush. These fruits are themselves rather interesting, as they will open up like a star when wet as – a means of releasing seeds only when conditions are suitable for germination.
COMPOST
Compost may be loam or peat-based, but must contain more grit for good drainage than would be required for cacti. A popular compost mix for many growers is 1 part John Innes No. 2 or 3 with 1 part grit or Perlite. It is recommended to add a top dressing of grit, coarse sand or small pebbles to enhance the appearance and to reduce the tendency for rot at the base of the plant. When potting the plant, it is best to bury the root in the compost and then to top up with a top dressing of grit, coarse sand or small pebbles, leaving only about a third of the length of the leaves exposed. This will enhance the appearance of the plant and reduce the tendency to rot at the base.
Fertilisers are not recommended for this group of plants, as they will then grow out of character. Instead, it is advisable to repot every few years.