See also Propagation of Cacti and Succulents
SEED RAISINGSeed raising is the largest single method of propagating cacti and succulents. Seed is available of a wide variety of cacti and succulents and is cheap when purchased from specialist suppliers. Mixed packets of seed from general garden seed suppliers tend to be rather expensive and the mixture of fast and slow growing types makes their cultivation more difficult.
Some cacti and succulent seedlings are fairly slow to get established and therefore need careful care. It is best to learn the techniques required first on more robust quickly growing species. Many growers have developed their own favourite methods and it may be necessary to experiment a little to find out what works best for you.
Firstly you need to decide what containers you are going to use. If you are growing large numbers of the same sort then the traditional rectangular seed pan can be used. This would be suitable for up to a couple of thousand seeds. If as is more likely you have a packet of 20-30 seeds then you can divide the area of this tray into small squares for each sort. The division can be done with small pieces of plastic or glass. Alternatively small individual pots can be used, small square ones are very convenient. The soil used can be the same compost as is used for larger plants but passed through a sieve to remove the larger particles. It is also important that the compost is prepared from clean materials free of weed seeds and fungi. It may be useful to sterilise it. When the compost has been placed in the containers they should be placed in a tray of water and allowed to become thoroughly saturated.
The seed may then be thinly and evenly sprinkled on the surface of the compost. The seeds should then be covered with a very thin layer of coarse grit. There is one exception to this in seeds of Mesembryanthemaceae such as Lithops which need light to germinate and these should not be covered. Most seeds germinate best at around 70F (21C). It may be necessary to use some artificial heat to reach this temperature particularly if the seeds are being started early in the year. If it can be arranged, some temperature differential between day and night will improve germination. It is necessary to maintain a fairly humid atmosphere while the seeds are germinating. Some growers achieve this by sealing individual pots in plastic bags. Trays can be covered with sheets of glass or plastic. Once the seedlings have germinated they can be introduced to the light and more air although direct sunshine is not a good idea at this stage. They should be kept reasonably moist and certainly not allowed to dry out completely.
It is a good idea to try and start seedlings fairly early in the year so that they have a reasonably long growing season before their first winter. Faster growing kinds particularly some of the succulents, columnar cacti and Opuntias can be ready for pricking out after six months either into individual small pots or trays. Slower cacti and succulents can be left in their original containers for a year or more.
A few types of cactus and succulent seeds can be reluctant to germinate. It is believed in some cases that the seed coat contains germination inhibitors. Sometimes the seed needs to be a few years old before it will germinate and in other cases cold/heat cycles are needed to prepare the seed for germination.
If seedlings are troubled with damping off fungus, watering with a copper fungicide solution may help. Also watch out for small black flying insects (fungus gnats or sciarid fly) whose grubs can rapidly destroy pans of seedlings. Yellow sticky traps are effective.
It is important that a good system of labelling is arranged so that the individual species can be identified. Being so tiny it may be simplest to give each container or divison a numbered tag and maintain an index elsewhere.
CUTTINGSMany cacti and succulents are readily propagated by cuttings. The process is a little different from rooting cuttings of non-succulent plants. With these the chief problem is that the cuttings wilt before they can form roots to absorb water. With cacti and succulents the main problem is the danger of fungal rots entering cut surfaces.
It is therefore important to keep any cut surfaces clean and to allow them to form a dry callous over the wound before placing the cuttings in soil. The length of time this takes to form will depend on the area of the cut surface and prevailing temperature and humidity when the cuttings are taken. In most cases it is best to take stem or shoot cuttings at a narrow point to minimise the cut area. The one exception to this is Epiphyllum cuttings which root better from a broad cut on the stem. Typically a week to two weeks should be left before planting the cuttings in moist soil.
Large cuttings with a broad area of cut can be left for a month or more. Some cuttings which root slowly may benefit from gentle bottom heat. Some leaf succulents can have stem cuttings planted almost immediately. Clumping cacti or spreading succulents may from roots while on the parent plants and these can also be potted up much more quickly. For plants very sensitive to rot a fungicidal powder or flowers of sulphur dusted on the stems can be useful. Hormone rooting powder is not usually necessary but may be useful in a few cases.
Most mesembs are easily propagated by cuttings, even the very succulent one such as Lithops, but it is important that a small amount of the woody tissue at the base of the leaves is included in the cutting. Single leaves of these may occasionally root but will not form a new meristem (growing point). Single leaves of some other succulents can however be propagated by this route. This includes Sansevieria, Gasteria and some Echeverias, Sedums and Pachyphytums. For Sanseverias and Gasterias even a part of a leaf may root and produce plantlets. The Echeveria group needs whole fresh leaves taken cleanly from the stem or in some cases from the inflorescence.
GRAFTINGGrafting cacti and to a lesser extent some succulents is a very useful technique for a number of purposes.
It can be used to grow difficult or weakly growing species by placing them on a vigourous rootstock. It can be used to keep cristate plants clear of the soil to avoid the dangers of rotting. It can also be used to force some species into rapid proliferation of offsets which can then either be grafted again or re-rooted on their own roots as cuttings. It is also the only way of keeping alive the genetic aberrations of completely variegated plants, i.e.those totally lacking chlorophyll.
It is sometimes not fully appreciated that the technique only works with families belonging to the Dicotyledonous plants (i.e. those having two seedling leaves. Families of plants belonging to the Monocotyledonous plants e.g. Asphodelaceae or Agavaceae lack the internal structures which make this possible.
Grafts are very commonly used in the Cactaceae and occasionally in the Euphorbiaceae, Portulcaceae, Asclepiadaceae and Apocynaceae. Grafts between plants of different families are rarely successful and indeed the more closely related the species are the more likely it is to be successful. Grafts are best undertaken when both the stock (the rooted part) and scion (the top part) are in active growth, probably in the spring or summer. The stock and scion should be of similar diameter and turgid. Many species can be used as stock plants but the genus Trichocereus is probably favourite. Echinopsis can be used but preferably a species which does not offset too freely. Quite a number of commercial grafts are done on three ribbed Hylocereus. This stock is very vigourous but its high winter temperature requirement often causes problems in amateurs' greenhouses. Another stock with slightly similar problems but not quite so demanding is Myrtillocactus geometrizans. This can be recognised by slightly glaucous six angled stems. Specialists in grafting tiny seedlings often recommend Pereskiopsis which can sometimes turn tiny seedlings into flowering plants in a matter of months. Very vigourous Opuntias can sometimes be the best stock for grafting plants of the Opuntiae tribe. Some interesting experiments have also been done recently using Echinocereus triglochidiatus as a stock for tricky, cold hardy plants such as some of the Pediocacti.
For stapeliads one of the larger, stronger growing Stapelia species is commonly used, an alternative being Ceropegia woodii tubers. For the Euphorbias something like E.ingens or E.canariensis are favourite.
A good clean sharp knife is an essential tool. The top is cut off the stock and then the edges bevelled off so that the surface does not become concave when dry. The bottom is then cut off the scion and the two cut surfaces pressed together. It is important that the vascular bundles of the stock and scion are adjacent as these have to unite in order for the flow of water and food to be conducted from the stock to the scion. Some system needs to be available to maintain this pressure for a period of a few weeks while the tissues unites. The most commonly used system is two rubber bands round the pot and over the top of the graft, at right angles to eachother. Many other ingenious ideas using weights and clips have been suggested. A little experimenting to find what you find convenient and practical is worthwhile.
Once the grafts have been made then they need to put in a warm place, out of direct sunshine and preferably not too dry an atmosphere. It usually takes a couple of weeks for the union to be sufficiently secure to release the pressure.
For some types of plants variants on this flat grafting technique such as cutting a v-shaped wedge can be used.