Watering when and how much

If any one factor determines success or failure in domesticating wild succulents, it is watering. Many people crave to know the magic formula of how much and when, expecting a simple equation depending on the size of pot, age of plant and —maybe—the phase of the moon as well. There is no magic formula. Successful growers are those who have come to know their plants, and can tell what to do from the look of them, the feel of the soil and the weather prospects. A stem or tuber just sprouting green leaves obviously wants to grow and is asking for refreshment; flowering and fruiting are usually (though not always) the culmination of the growing season and a sign for a rest. When in doubt, it is safest not to water. It is often a matter of waiting for the plant to make the first move.

In a general collection most of the succulents can be accustomed to the typical European and American routine: grow in summer, rest in winter. This means that, as long as they have healthy roots and are favourably situated for light, warmth and aeration, they can be given a good soaking in the summer months as often as the soil dries right out. Aim to soak all the soil: merely damping the surface encourages surface rooting. In autumn, watering should be tapered off. Thereafter, the thinner-leaved and less xerophytic species need occasional watering to prevent excessive wilting and leaf drop, but highly succulent types can be kept almost or quite dry until spring, j Spraying the air to increase humidity on mild, bright days in winter is helpful, especially in electrically heated glasshouses where evaporation is high, and in centrally heated rooms. A watering can with a long, slender spout is ideal for getting the water inside the rim of small

Overhead watering with tap water may leave unsightly grey markings on stems and leaves if the water is hard.

Right(6.2): The Lithops salicola on the right s I well grown and resembles the plant as found in nature That on the left has been overfed I

Below right (6.3): These tuberous crassulas die , down to soil level for part of the year, and proper t observance of a dry resting period is important

Below: Many cacti benefit by being kept coot I and dry in winter, like these natives of Colorado (top, 6.4). A month after the first watering of spring (bottom, 6.5) they are plump again. The shrinkage is normal.

Some cultivators prefer to use rain water, but it should be stored in a covered vessel and free of algae and other contamination. Watering from below is an excellent alternative to overhead watering, where it can be arranged. Some form of trough is needed that can be filled and then drained completely after the top soil in each pot shows damp. If the collection is small enough, each pot can be plunged separately in water to achieve the same effect. Remember, though, that this technique rapidly impoverishes the soil by washing away nutrients in solution. If annual repotting is not practicable, a programme of controlled liquid feeding must be adopted.

Some dwarf cacti shrink considerably during the winter rest, and in the natural habitat may even disappear below soil level. The contrast between the plants when dormant and after the first waterings of spring is often striking (6.4, 5). The shrinkage is normal, and one should not be tempted to water out of season — they will revive when the time is ripe.

Succulents under cover A sunny windowsill is often the starting point for a collection, and many succulents are admirably suited to the highly unnatural conditions of directional lighting, draughts and extremes of microclimate typical of a twentieth-century centrally heated sitting room. A site over a radiator does not suit the "desert" cacti, which pass the winter best in a cool, dry, dormant state; here the choice is better limited to tropical euphorbias (E. milii

20. 6. and allies). Sansevieria. Peperomia and the like.

On a windowsill that receives no direct sun the choice is even more restricted. Casteria and Haworthia thrive if frost is excluded, but weak and untypical growth results for most other succulents. Such sills can, however, be put to good use for overwintering potted succulents that spend their summers out in the open. In Canada and the USA some collections are grown under artificial lighting to be entirely independent of direct sunshine. Some cacti can be flowered from seed without ever having seen the sun.

Keeping out the cold. In frosty areas a glasshouse—or its diminutive, a frame-is the dream of every cactophile. Where winters are not too severe, an unheated structure can cater for a modest range of cacti, agaves, echeverias. etc — the sort of plants mentioned below as hardy succulents. In some countries where winters are very cold, heating costs are prohibitive, but enterprising growers dig up the plants from their unheated glasshouses in the autumn and store them dry. wrapped in paper, in a frost-free basement during the winter. It says much for the adaptability of cacti that many of them put up with this drastic treatment and seem little the worse for it.

A glasshouse can be home-made (6.6) or purchased, free-standing or lean-to. glazed all over or on top only, and highly diverse in size, shape and construction. Every degree rise in minimum winter temperature means a bigger fuel bill, and the grower must consider whether he really needs the delicate tropical succulents and, if so, how to house them most economically. A polythene tent in one comer of the glasshouse, directly over the heat source, is one answer. Another is to take the treasures into the home for the winter. My own 7i4m (24ft) metal-framed glasshouse (6.7) is divided into three sections by glass partitions with doors: one half is kept cool (that is, with frost exclusion only) for the general collection, a central quarter is kept warmer for propagation and tropical succulents, and the end quarter has no heat, apart from what filters through from the warm section. Although drops below freezing occur, this cold section sustains a varied collection, mostly of cacti, and they respond with copious flowers after being kept dry and dormant from about October to March. In the cool section I aim to maintain a winter minimum of 4°C (40°F), although brief drops below this may occur in the coldest weather. In the central warm part the minimum is around 10°C (50°F). The large propagator is set at 21°C (70°F), with the shelf above it reserved for melocacti and discocacti.

Right (6.6): This glasshouse, built by an engineer, is glazed in plastic and can be opened in summer to admit more air Most commercial greenhouses have too lew vents

Below (6.7): Succulents displayed in the cool section ol the author's glasshouse Guests are expected- hence the exhibits. The square plastic pots save space and are unobtrusive

A second, reserve source of heat is advisable, particularly in these days of power cuts and fuel crises. A popular arrangement I have adopted in my two heated sections is an electric fan heater supplemented during the coldest months (January to March in England) by an oil lamp. As the electric heaters are controlled by a thermostat, they cut out when the oil lamps provide enough heat, and come on only during the coldest spells. Thermostatic control is also possible for oil lamps now. Natural gas, where available, has proved a reliable economical source of heat, because the fumes do not need to be ducted outside the glasshouse, as they do with coal gas. Indeed, they provide carbon dioxide, a plant food, liie old-fashioned coke or coal boiler is more suited to larger collections and nurseries, but is more trouble to keep going.

Light and air. In selecting or designing a glasshouse, light and ventilation should be given high priority. Most succulent growers favour metal frames because they are narrower than wooden ones and obstruct the light less. Manufacturers tend to economize by not including enough ventilators: it pays to have extra ones fitted to allow a good through draught in summer—the best safeguard against scorching. Sheet plastic has certain advantages over glass because it is light and easy to work and transmits more ultra-violet radiation (6.6). But plastic is expensive and needs replacing when it becomes discoloured, hazy or brittle. The polythene-covered balloon house favoured by some commercial growers is suitable for mass raising of seedlings. Many amateurs line at least a part of their glasshouses with polythene in winter. This "double-glazing" reduces heat loss and prevents drips from an old and leaking roof, although additional drips from condensation may form within. The main drawback is reduction of light at the time of year when it is most needed. A properly double-glazed glasshouse would probably pay for itself in a few years from the saving in fuel bills.

A glasshouse should preferably run east-west and be sited well clear of trees, walls and other sources of shade—a placement not easy in crowded urban areas. Painting house and garden walls white as reflectors can make up for some loss of light. A good compromise isa lean-to structure facing south.

Aims and methods. How a glasshouse of succulents is maintained depends on whether your plants are being grown for exhibition, or private amusement or for study, and how much time you are prepared to spend on their upkeep. It is possible to maintain a large and varied collection in presentable shape with suprisingly little fuss. That is why succulents are ideal for the businessman who has to be away from home for frequent short periods. Watering is by hosepipe—all or nothing—and repotting when it cries out to be done. Automatic vents take care to some extent of daily temperature fluctuations, and an annual soaking with systemic pesticide keeps down the worst of the attackers. The busy owner may only really see his plants when taking visitors around, but the knowledge that they are there, a source of silent admiration, of escape from harsh reality and the noisy routine of city life, provides just that outlet we all so dearly need. I doubt if any other type of plant collection can offer so much in a small space and in return for so little.

At the other extreme we have the single-minded plantsman who lives for his plants, and is prepared to spend long hours grooming and caring for them. Many such devotees become experts in the more tricky and temperamental groups: the dwarf Mesembryanthe-maceae, the Stapelieae. the tropical caudi-ciforms. It is to these dedicated folk that the conservationist turns as the hope for preserving rarities from habitats fast disappearing under the plough. For the

Right (6.8}: Art attractive miscellany ol Monocotyledons displayed at La Mortola in Italy: small aloes in the foreground, large grey agaves behind, and for the background tall yuccas and Iright) a Dasylirion with oddly plumed leal tips

Below (6.9): Cylindrical jointed Opuntia species and columnar cerei in a large private garden on Majorca. Frosts are not unknown, restricting to some extent the choice of succulents in the open

exhibitor, watering must be done individually and repotting at least once a year, giving him the chance to weed out unsightly or malformed specimens, and discard or repropagate them. He resists the urge to overcrowd or put up too many shelves that would shade the plants below. There are a surprising number of such specialist collections around, unknown to the general public. The immaculate glasshouse of a perfectionist has to be seen to be believed.

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