If you are a plant enthusiast with a consuming interest in nature's unusual and dramatic manifestations, surely the category of cacti and other succulent plants intrigues you. Nowhere else in the plant world will you find a more fascinating array of weird and unusual forms, or more exotically colorful blossoms. Furthermore, few other plants are so rewarding in return for so little attention.
Trieste plants are native to desert and to jungle, where they are subjected to long periods of extreme heat and drought, and they have accommodated themselves to their environments by producing very small leaves and coverings of fleshy stems, spines, or scales to reduce evaporation of stored moisture so essential to life during dry spells. Many cacti and succulents are small enough, and stay that way, to be ideal for the greenhouse growers interested in collecting many kinds. As to the distinction between them: all cacti are succulents, but all succulents are not cacti.
Despite cold desert nights, cacti and succulents grow best in a greenhouse of at least 60 F at night. Soil mixtures vary slightly, depending upon the origin of the plants. Those from the desert thrive in an equal-thirds mixture of peatmoss, sand, and garden loam; those from jungle areas should have an equal part of leafmold added to the desert mix. Desert cacti take full sun all year, but they do not suffer if given the light shading required by the jungle types. Desert cacti, inured to extreme heat, burning sun, and only occasional periods of heavy rain, are grown on the dry side. Jungle types are better kept evenly moist since the dense growth and high humidity of the tropics tends to maintain moisture. An occasional period of drying out is apparently beneficial, but put plants on a twice-a-month feeding schedule starting in February when growth begins after the winter rest and continuing into September. In winter give little water while plants are in an almost dormant period.
Each species or variety of cactus has its own blooming season. If you grow cacti primarily for flowers, special handling is necessary. Plants must rest for three months prior to their flowering time at a daytime temperature no higher than 60 F; give plenty of light but hold back on the water. At the first indication of new growth, resume your schedule of watering and feeding and provide normal temperatures. Repot plants when it is evident they are rootbound; do this between February and June, though September is also satisfactory. At other seasons, disturb the roots as little as possible. Small plants should be repotted to the next larger pot each year; repot mature plants every three years. Several methods of propagation can be used to increase your collection: cuttings, root divisions, offsets, grafts, or seeds.
Seed germination takes only about 10 to 20 days. Damp-off is the biggest problem to overcome. Use a sterilized medium. Water thoroughly, cover with glass, and shade with newspaper until germination, then remove the coverings. When spines appear on seedlings, transplant to flats containing a soil mixture as recommended above for mature plants, screened to remove lumps and large particles. Withhold water for several days after transplanting, then water regularly.
Make cuttings with a clean, sharp knife. If the plant has branches, cut off a branch from the main section; if it grows to a single stem, take a 2- to 3-inch cutting from the upper part of the stem, usually during spring or summer. To avoid stem rot, place cutting in a shady, dry location and let the cut heal until the base looks thickened this takes from a week to a month. When cut is well healed, insert in sand or sterile medium such as perlite, and water sparingly for a few days, giving only enough moisture to prevent shriveling. When cuttings have rooted, move to small pots.
To propagate by offsets, separate them gently from the main plant and pot individually in regular planting mix. Try grafting to produce novel and unusual cacti. The operation is simple and almost always successful. Two or more types can be grafted together, and almost all kinds are compatible. Slice each specimen horizontally to provide the flat cut surfaces which are fastened tightly together. Use rubber bands or string over the top and under the pot and crossed at right angles, to assure close contact until the graft "takes." Or make a V-shaped cut in the potted plant, and shape the bottom of the piece to be grafted to fit into the V. Tie together and do not disturb until healed.
Cleanliness is extremely important in growing cacti and succulents. Insect infestations are troublesome, and the plants will not tolerate some of the newer pesticides such as parathion or malathion. Mealybugs, scale, spider-mites, thrips, and aphids may be controlled with rotenone, pyrethrum, or nicotine preparations. Prevent nematodes and damp-off by steam sterilizing soil before use. Once infested with nematodes, plant must be destroyed.
There are thousands of cacti and other succulents suitable for growing in a greenhouse, so you should obtain catalogues from specialists and use the detailed descriptions and illustrations to help you select what you would like to grow. I can recommend the species and hybrids of these genera:
Cacti: Aporophyllwrn, Astrophytum, Cephalocereus, Cleistocactus, Echinocactus, Echinocereus, Echinopsis, Gymnocalycium, Hylocereus, Lemaireocereus, Lobivia, Mammillaria, Notocactus, Opuntia, Parodia, Rebutia, Rhipsalidopsis, Selenicereus.
Succulents: Adromischus, Aeonium, Aichryson, Cotyledon, Crassula, Echeveria, Faucaria, Fenestraria, Gasteria, Graptopetaium, Haworthia, Hereroa, Kalanchoe, Kleinia, Ophthalmophyllum, Oscu-laria, Othonna, Pachyphytum, Portulacaria, and Sedum.