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How to grow CACTI and other succulent plants from seed
(originally on The British Cactus & Succulent Society website)
- Containers Seed can be sown in a seed-box with partitions formed by the labels, but a better idea, since there is less likelihood of the seeds "jumping" from their own compartment, is to sow in small pots, one species to a pot. It is a good plan to stand the containers on a tray of damp sand, so that they do not dry out from below. A plastic sandwich box is good for this purpose.
- Composts Whichever compost is chosen, it should be light and well-aerated. John Innes Seed Compost, with the addition of ½ gritty sand is an old favourite, but many people use the modern no-soil composts with good results. With these, it is imperative not to firm the mixture down. For those who prefer to mix their own, equal parts of well-rotted leaf-mould and sand, or peat and sand, with J.I. Base added, will serve. The compost must be sterile.
- Sewing the Seed Scatter the seed in the usual way onto the top of the compost or, if the seed is larger, sow individually and push the seeds down a little way. Do not cover small seeds, or cover with a light scatter of fine grit-this last has the desirable effect of greatly reducing algal growth. The pots should then be soaked from below in fungicide to kill any damping-off fungi. Cheshunt Compound, which is readily available in the shops, serves well and should be mixed at the rate of 1 level teaspoonful in a quart of water. When the pots are throughly soaked, drain them and arrange in whatever container you have chosen. Cover this with glass and put it in a warm shaded place for the seeds to germinate. If a sandwich box is used, the top will serve in place of glass. Darkening the pots with newspaper or other material is doubt fully helpful, especially if the seeds have already been covered with gravel.
- Propagators If possible, germinate the seed in a propagator with bottom heat. Care should be taken to prevent the pots drying out from below. The majority of seeds germinate best at a temperature between 70 and 75'F, and some seedlings may appear within a week or 10 days. At lower temperatures, germination usually takes considerably longer. Failing a propagator, many people make use of a warm place such as the airing cupboard, or near the kitchen boiler, but the seed pans must be moved into a good light as soon as the first germinations have taken place. From late Spring onwards, a sunny window-sill or greenhouse may be used, but in such cases, the seedlings must be protected from direct sun, for which a double thickness of butter muslin will serve as well as any thing.
- Germination and after Be careful to keep the top of the compost damp; a fine overhead spray will suffice when the pots show signs of becoming dry. Make sure that the sand in the tray remains damp. As soon as the first seeds have germinated, raise the glass or lid slightly to permit some circulation of air. From now on, the tiny seedlings need to be in a good light, but shading from all but winter sun is desirable for the first 12 months. If the young plants are exposed to too much sun, or the compost dries out, they may stop growing and often turn red; once they stop, it is often difficult to persuade them to start growing again. After germination and at intervals of about 10 days, it is as well to spray with a fungicide. Captan is good and appears to contain nothing which will harm the tiny plants. It is as well to continue this treatment for 8-10 weeks, or until the seedlings look like miniature cacti. Never let the pots dry out-but don't saturate them either. A sodden compost is as harmful as a dry one. Try to keep the atmosphere in a propagating box damp as this helps to ensure that roots do not dry out before they have penetrated to a reasonable depth in the compost.
- Pricking out This can be done "when the seedlings are large enough to handle" - as the books say. Otherwise, when they are overcrowded, or if the soil looks sour. Some growers keep their seedlings in the sowing compost for 12 months, others always prick out when the seedlings are 3 months old. Any good compost will do at this stage, provided it is well drained and well aerated. Above all, keep the seedlings growing.
- Winter care of Seedlings Ideally, your seedlings should be kept at a minimum of 60F during their first winter, in which case they may be carefully watered and kept growing. However, some experienced growers give their seedlings little or no extra heat during the winter, and water only during sunny spells to keep them just ticking over. Try to ensure in such cases that the compost is nearly dry by nightfall. The most dangerous months for your seedlings are likely to be February, March and early April, when the nights are cold and the day temperatures under glass rather high. As the days lengthen, the seedlings really respond to watering and start to grow visibly, and it is then that a sharp drop in temperature can be fatal if the compost is too wet. By mid-April, one can usually give the normal Summer treatment.
- Pests The most dangerous insect pests for young seedlings are Sciarids or Mushroom flies, which lay their eggs in damp compost and seem attracted to compost containing leaf-mould. The grubs which hatch out seem particularly partial to small seedlings and will either eat the entire plant or leave nothing but an empty shell. The flies are small and black and hover or walk over the compost. They can be dealt with at the grub stage by spraying the seed-pan with a systemic insecticide, which may also kill some adults. This appears to be harmless to the seedlings. The risk of sciarid attack continues for as long as the seedlings are kept damp, though it seems unlikely that the grubs will attack a well-grown 18 month old seedling. Small slugs are another potential cause of considerable losses, though these can usually be seen without difficulty and precautions are straightforward.
- General Some species of cacti, especially of Mammillaria and Rebutia, will flower two years old from seed, rarely sooner, and the former are especially easy to raise in many cases. Most of the taller growing cacti, species of Cereus and Cleistocactus, for example, have to reach a considerable size or age before they will flower, but these are frequently grown for their shape or white spines.
Do not be disheartened by losses. Cacti are very vulnerable at the seedling stage and plants may die for a variety of reasons. Remember that not all the seeds in a packet may be viable, while even if they germinate not all the young plants may be capable of reaching maturity. One does not expect 100% germination or survival from packets of seeds of other plants. Practice makes perfect! These plants are more difficult to raise from seeds than ordinary bedding plants. Work out your own method, improving it a little each year and you will eventually achieve considerable success.
NOTE. Epiphyllums from seed These plants dislike lime in their compost, so composts based on the J.I. formulations are unsuitable for them. Levington compost is ideal both for sowing the seed and for growing the plants on afterwards, though it is rather difficult to keep it free from algal growth.
Other succulents Most of the other succulents can be grown from seed in a comparable way, except for some of the most difficult, the raising of which will tax even the most experienced. Seedlings of stapeliads are very large, even when very young, so make sure they have sufficient head-room if they are to remain covered.