Growing Cacti and Succulent Plants
Over the past few years cacti and other succulent plants have become increasingly popular. In the centrally heated conservatory and home they make ideal subjects and revel in the dry air. Their stylized shapes are remarkably in keeping with modern architecture. And all the old wives’ tales about flowering only once in seven years have been exploded.
There are certainly many species of cacti that do not flower until they reach a considerable size, but equally so there are many that flower profusely as very small plants. Once plants do reach flowering size they should flower regularly every year providing they are well looked after.
In the wild, cacti are found growing in a wide variety of conditions and climates. Those growing high up in the Andes of South America are covered by snow in winter. Some are epiphytic and grow in humus trapped in the crooks of trees — these are known as orchid cacti and are very popular as house plants because of their exceptionally large and colourful. The majority of cacti, however, are found in naturally arid conditions such as exist in many parts of South America, Mexico and California.
A great many succulent plants are wrongly called cacti, simply because they have spines or thorns. A true cactus can always be identified by the way in which the spines grow, with clusters of several spines arising from central points along the ribs or on tubercles. These central points are known as areoles, and any plant that does not have them is not strictly speaking a cactus, although amongst these succulent plants there are many interesting and bizarre forms. There is one plant that grows like a string of beads, and another that has hairy flowers smelling of decayed meat to attract the horseflies that pollinate it. There are also the ‘living stones’, plants that grow in the very hot dry deserts of South Africa and have taken on the semblance of small pebbles to prevent themselves from being eaten by animals.
Cacti and succulents will thrive in any dry atmosphere— on a greenhouse bench, conservatory bench, or indoor gardens of various designs, the pattern being set by the cactus houses of many botanical gardens, that in Kew Gardens near London being an outstanding example.
Purchased cacti will probably be in a tiny pot that does not allow sufficient development room for new roots. Ideally repotting should be done in late autumn or early spring when the plants are semidormant, though they do not seem to suffer from being moved carefully during the summer.
The potting compost should allow freeof water, otherwise the plants will quickly rot. A mixture of equal parts of good loam and gritty sand is suitable for desert cacti. Succulents need to be kept slightly damper than cacti so one part of peat should be added to this mix for them. Epiphytic cacti need a compost rich in humus, and 2 parts peat, 2 of leafmould and 1 of loam is ideal. Purchased John Innes composts are acceptable provided extra sand is added. Re-potting long-spined cacti may seem a formidable task, but if a piece of twisted paper is wrapped round the middle of the plant leaving a ‘handle’, the job is made much easier.
Once in a reasonable sized pot, eg 9cm (34n) for globular varieties, further re-potting should be in the same size, being simply a replacement of exhausted compost. Flowering ability is adversely affected by too large a pot. Bowls or indoor gardens should be planted with the tallest plants at the back, low growing plants in the centre, and trailing plants hanging over the front and sides, finished off perhaps with a layer of flint chippings or small pebbles between the plants.
As with most other types of plants, watering should be done when needed rather than on a regular weekly or fortnightly basis. The amount of water required varies from nothing during the winter to a maximum at the height of summer of a good soaking when the compost is dry. After the winter rest, watering should begin very gradually in warm weather around early or mid-spring. When the plants have started growing strongly the amount of water is increased until midsummer, after which it is gradually reduced until by early autumn they are getting very little. By mid-autumn no more water is given until the following spring unless conditions are exceptionally hot.
It is not really necessary to feed cacti as long as they arc re-potted occasionally to provide newfor them. After flowering, however, a couple of waterings with very diluted liquid fertilizer does help to get the plants back into peak condition.
Despite the fact that they live in hot climates, cacti need plenty of fresh air. In a greenhouse give ventilation even on sunny days in winter and do leave both ventilators and door wide open at the height of summer, provided the range of other plants being grown allows this.
Though many varieties of cactus in the wild are covered by snow in the winter, they do not in damp temperate climates dry out before the cold weather as they do in their native lands. So, if exposed to frost, the water inside the plant will freeze, resulting in the death of the plant, and for this reason cacti should be kept at a minimum temperature of 4.4-7.2°C (40-45°F) throughout the winter. Some of the more exotic succulent plants, and the epiphytic cacti, need to be kept at 12.8-15.6°C (55-60°F). This means that unless expense is no object warmth-loving cacti are better lifted into the dwelling house over the winter.
Basically there are four methods of propagating cacti: by dividing up old plants, taking cuttings, raising from seed or by grafting.
This is the easiest way of propagating, as the offshoot has its own roots before it is detached from the parent plant. Unfortunately not very many types of cacti produce offshoots, and those that do are not perhaps the most interesting. The best time for detaching offshoots is in the early spring, as the young plant has the longest possible time to establish itself before the winter resting period.
Most cacti and succulents can be propagated quickly and easily by cuttings, but there are some difficult varieties which tend to rot before they produce roots. Before taking cuttings from a favourite plant one should consider whether this will leave ugly calloused stumps. Cuttings should ideally be taken in late spring, though they may be taken until quite late in the year providing bottom heat is available. It is best to take cuttings at a joint in the case of Opuntia species (prickly pear) but with tall upright types which do not make joints, a 7.5-10cm (3 or 4in) cut from the top of the stem will make a good cutting. Let them dry on a shelf for a day or two before attempting to root them in seed trays, pots of pure sand, or half peat and half sand.
Cacti can also be grown from seed. Mixed packets are available from most garden shops, but several firms deal in packets of single named varieties. The easiest way of building up a large collection quickly and inexpensively is indeed from seed. Some varieties will flower within two or three years of being raised from seed, but the majority take a great deal longer. Cactus seeds are very easy to germinate, the main problem being to keep them alive after they have germinated. Scatter the seeds over the surface of a pan or box or peaty compost, stand it in a few inches of water, and put a sheet of glass over the top. With efficient heat germination generally occurs within a month. Both before and after germination watering must be controlled so that the soil is never dry, or conversely. The glass is then removed and the young cactus plants, which are very slow growing, can remain in the pan for a year before pricking out.
Grafting is a rather specialized technique. It is used to speed the growth rate of slow-growing varieties by grafting them on to a vigorous root system of another species or culture. Grafting is often done by specialist cactus nurseries to enable them to produce saleable sized plants more quickly. Plants which are forced in this way often bear little resemblance to the same variety grown on its own roots. Spines especially do not seem so strong on grafted plants. One advantage of grafting is that plants flower earlier than they otherwise would.
The stock which provides the root part of the graft is generally one of the faster growing Cereus group, chosen with a stem the same diameter as the scion. The top is cut off the stock leaving about an inch above soil level; the top of the scion is removed and the two surfaces joined as quickly as possible to prevent drying out. The two parts are held together either by a cactus or spine pin or an elastic band running under the base of the pot and over the top of the scion. The graft should be kept in a warm dry place until the two parts have united, taking care that no drips enter the cut when watering, which invariably starts rotting. Grafts usually take 4-6 weeks to unite and can be made at any time of year when both stock and scion are growing vigorously.
Prickly pear types
Many of these have short bristly spines that come away easily in the fingers. Whilst not poisonous, they are difficult to remove and cause severe irritation. Very few of these plants flower at the sort of size suitable for the home and are grown mainly for their attractive pads. Opuntia ficus-indica is the plant cultivated in parts of the world for its edible fruit, and is the true ‘prickly pear’. The pads are large, up to 45cm (18in) long, and have short spines.
Opuntia microdasys albispina has small dark green pads with pure white bristles at the areoles, giving the plant a spotted appearance.
Opuntia salmiana is a relatively dwarf-growing type which flowers freely even as a small plant. The flowers are pale yellow and measure about half an inch across.
Cacti grown for spines and hair Echinocactus grusonii makes a large plant, covered in long golden spines.
Espostoa lanata is covered with long white hair which completely overhangs the spines.
Ferocactus wislizeni has long hooked spines, is very slow growing and will not flower until it is very old indeed.
Myrtillocactus geometricans is a very fast-growing variety with very short black spines and a pale blue/ green stem covered with a powdery ‘bloom’ that comes off if the plant is handled too much.
Oreocereus trollii is another hairy variety but it also has very long bright red spines growing out through the hair.
Free flowering cacti
Aporocactus flagelliformis is commonly known as rat’s-tail cactus because of its long thin stems that trail over the edge of the pot. In early spring the whole plant is covered with large red flowers, and for these to be seen at best advantage the plant can be grown in a hanging basket.
Echinopsis eyresii produces masses of offset, so is very easy to propagate. If a large clump is allowed to build up the mother plant will flower regularly.
Rebutia miniscula is a very small plant, no more than 7.5cm (3in) across even when fully grown. In time it will produce a great many offshoots and so build up a large clump. It is one of the most free-flowering cacti and will flower within two years of being grown from seed.
Stenocactus multicostatus is unusual in that it has wavy ribs. This plant too will flower when quite young.
Epiphytes, the orchid cacti
These plants are quite unlike the desert cacti in appearance, having flattened leaves like stems with no spines. When not in flower they are relatively uninteresting, but are well worth growing for the flowers alone, which are several inches in diameter and come in shades of red and orange, also white. Some are scented. There are not many natural varieties of epiphyllums, but a great many hybrids have been raised, especially as florists’ plants.