| Succulents
Introduction: Succulence in plants occurs due to lack of adequate supply of moisture together with heat and sunshine. It is necessary for the plants on high mountains to withstand drought and vegetation of succulent appearance are commonly seen. In the seacoast or salt deserts salinity results in the formation of succulent plants. Most of the succulents occur in the South African deserts and in the Cape Province. Succulents also occur in the deserts of the Sahara. Various forms of giant succulent plants are native to the Isle of Socotra. Many beautiful and interesting succulents come from Canary Isles. In the stony and the calcarious soil of he Southern and the Western sides, numerous succulents such as, Agave, Echevaria, Sedum and xerophyllum thorny bushes grow in abundance. Succulents are among the most specialized plant form and they are the expression of peculiar condition of soil and climate. As the plants grow in the severe shortage of water in the deserts and semideserts they are adopted to conserve water and to reduce transpiration. The water storage tissue occupies almost the whole leaf or the shoot and is surrounded by a thin layer of assimilating tissues. The leaves or the shoots may contain water as much as 95% of their volume. The water content in the leaves is very mucilagenous, which is very important for its retention of water. During the dry period, the plants are usually completely at rest and look dead since they have shrunken and the surface of the leaf dried up. But they recover very quickly after the first rain, in a short time produce new leaves and show new growth by the swelling of the plant body. In ornamental horticulture, these succulent plants are used for their peculiar shape, decorative foliage or showy flowers and constitute the most important plants in the rock gardens. Soil and manures Light porous soil is best for succulents. Undecomposed organic matter should never be used. Well-decomposed leafmould and cow manure, loamy soil, sharp sand, crushed, brick and charcoal constitute the ingredient of the compost for succulents. For many species, addition of lime is recommended, the best form being mortar rubble. For most of the Crassulas the following compost is recommended: Leafmould 3 parts, well-rotted cow manure 1 part, Loam 1 part, Crushed brick 1 part, Sharp sand 6 parts. For Euphorbia, Aloe and Agave use a compost consisting of 1 part each of cow manure, leafmould and loam and 2 parts sharp sand; Echeveria, Aeonium and similar less sensitive plants generally require loamy soil which is not too prorous. Propagation i. Propagation by seeds- Since almost all succulents flower and produce seeds, propagation by means of viable seeds is a practical method. Raising from seed becomes essential when large number of plants of one species are to be grown for commercial purpose. The best time for sowing seed is the spring. At a temperature between 30 to 35oC and the relative moisture content of the air of about 90% most seeds germinate quickly. After germination of seeds the seedlings should be removed in drier place. The seeds compost should also be very porous mainly containing well-rotted dry leafmould mixed with twice the quantity of washed coarse sand. Shallow pans are commonly used for sowing seeds filled with the compost and covered with a thin layer of sand. The seeds are then scattered thinly on the sand again covered with sand to a depth not greater than the size of the seed itself. After sowing, the pots should be kept in glass frame or covered with a glass pane. Watering is done either by spraying through a fine rose or keeping the pot on a vessel containing water. When the seedlings come up, the young plants are transplanted in a compost cotaining 3 parts leafmould, 1 part old cow manure mixed with soil, 1 part mortar rubble, 1 part loam, 6 parts clean sand. The young seedlings should be kept dry during the resting period. Like older plants the young seedlings, however, should not be exposed to extreme climatic conditions. ii. Vegetative Propagation- Almost all succulents can also be propagated vegetatively. As the succulents are fleshy, the parts removed must be carefully handled. The growth is cut off with a sharp knife and kept in an airy, dry place so that the cut surface becomes dry and covers itself with a shine. Cuttings should be taken from mature growth, little woody rather than too soft, for soft cuttings rot easily. It is not always necessary to use the terminal cuttings, lateral shoots may also be used. Aloe and Agave produce offsets and these are used for multiplication of plants. When large enough, these offsets are separated from the plants, a little below the surface of the soil and treated as cuttings. In many cases offsets are found to produce roots while attached to the plants and they can be potted after separation. Though it is not possible to multiply all types of succulents from leaf cuttings, species of Crassulaceae lend themselves successfully to this method of propagation. The leaves are carefully detached from Crassula, Cotyledon, Echeveria, Sedum etc. And dried like the stem cuttings. Haworthia and Gasteria also produce shoots at the base of the cuttings. A few succulents such as Kalanchoe bears on the edges of the leaves small adventious buds which may be detached and used as cuttings. The rooting medium for all types of cuttings whether from shoot, leaf or buds should contain sand and dry leafmould in the proportion of 2:1. As a rule shoot cuttings root quicker than leaf cutting and the rooted cutting should be carefully removed and potted in the compost recommended for the plant. Watering Watering of succulent plant is one of the most important points. Hawarthia, Gasteria should not be allowed to dry too much and the soil should be only moderately moist. During the winter month, the soil for Huernia and Stapelia should be kept just moist so that the roots are not dried up. Euphorbia should be watered freely during the growing period but very little during the resting period in the winter months. When watering is done the soil should be soaked thoroughly and sprinkling of water on the surface soil be altogether avoided. Whenever possible rain water should be used in pots. Repotting Like cacti the resting period of most of the succulent comes in winter and the growing period during the spring and the summer months. This is, however, not true with all types of succulents as some species begin to grow in June, July and August and their resting period is in the spring and the early summer. Like other plants succulents should be grown in clay pots which are porous, i.e., water and air pass through them. The pots must be provided with drainage holes so that superfluous water can pass out readily. The shape and size of the pots should be in proportion to the root system of the plant. Aloe, Agave etc. should be grown in large posts on account of their large roots. Many Euphorbias also need deep pots. For shallow-rooted plants like most of the Gasteria, Haworthia, Stapelia shallow pots should be used. Repotting should be carried out at the beginning of the growing period. Quick-growing plants should be repotted once every year. Species which grown less freely need not be repotted every year. The plants should be taken out very carefully with minimum injury to the roots and then firmly replanted in a bigger sized pot in the compost of the same composition. Common Succulents Adenium obesum –Fleshy, thick-twisted stem grown in rock garden, about 2 m high; flowers pink. Aeonium –Succulent herbaceous plants with woody and branched stems, leaves in the form of rosette at the ends of the branches. Some species have no distinct stem and rosette arises close to the ground.
Agave—These are the common succulent plants with xerophytic appearance, leaves in the form of rosette, firm, hard and sword-shaped, usually spiny at the margin and tip, sometimes smooth at the margin but the apex is stout and pointed. The plants die after flowering. Adventitious buds often form at the axils of the panicle branches.
Aloes are a group of succulent plants, hardy and widely found in tropical countries, plants stemless or with short stem or sometimes tree-like. Leaves mostly in rosette, fleshy, margin entire or toothed surface may be spinous sometimes with markings or stripes.
Caralluma—Succulent perennial herbs, 4 to 6 angled dentate sometimes creeping stem or semi erect grow in clump.
Ceropegia—Succulent perennial harb, stem leafless or twining with opposite leaves, lanceolate or cordate. Flowers showing various colours. Cissus cactiformis—Climbing succulent plants 4-angled, winged, constricted at the internode. Cissus quadrangularis is also a climbing shrub, 4-angled constricted at the nodes, leaves cordate, falling off. Cotyledon—Succulent herb or shrub, usually grows in clumps. Leaves spirally crowded, thick and fleshy. Flowers pendulous from terminal branches.
Crassula—This genus has more than 300 species and forms the most important group of succulents. These are usually herbaceous plants or semishrub with succulent branches and twigs. Leaves, opposite often crowded into a rosette usually sessile. Flowers small, mostly numerous in terminal or lateral cymes. Echeveria—Perennial herbaceous much branched succulents. Leaves spirally arranged in rosette, fleshy and thick, various shapes and size. Flowers appear from the leaf axils, usually bell-shaped.
Euphorbia—Euphorbias are also common succulents in tropical country. They are usually thorny, fleshy. In many cases they resemble cacti in many ways. Few species have large prominent leaves.
Fourcroya—Plants are like agave with tufted leaves, margin spiny or dentate leathery.
Gasteria—It is a showy succulent, leaves long, thick firm mostly distichous.
Graptopetalum—perennial plants, look more or less like Echeveria. Leaves in rosette, thick and fleshy.
Haworthia—Low-growing perennial herbs, leaves in rosette or in compact rows, fleshy with smooth tubercles, tip usually stiff.
Kalanchoe tubiflora—Erect plant, mostly unbranched, leaves almost cylindrical, somewhat broad in the upper surface. Nolina –small tree, succulent stout trunk swollen at the base and tapering towards apex. Leaves long, narrow, leathery.
Pachyveria—Intergeneric hybrid between Pachyphytum and Echeveria. Plants look like Echeveria and Pachyphytum. Leaves succulent, fleshy in rosette on short stem. Pedilanthus—These are succulent shrub or sub-shrub with latex.
Pelargonium—Several species of Pelargonium commonly grown in milder climate have succulent stems. P. juttae has globular stem. Portulacaria afra-Succulent shrub; stem horizontal spreading. Leaves opposite, obovate, thick, glabrous, shining green. Sedum—These are annual, biennial or perennial herbs or shrubs. Branches herbaceous or slightly woody, dichotomously branched erect creeping. Leaves mostly alternate, flat or cylindrical and in most cases they are closely set on the stem.
Sempervivum—These are a group of low-growing perennial herbaceous plant found in the rock gardens of temperate countries. The leaves are arranged in the form of rosette, thick fleshy, green, reddish or bluish in colour, glabrous or hairy. Senecio -This genus comprises 1300 species and distributed all over the world. Stapelia—Perennial succulent herb, stem fleshy erect, branched at base and forming clumps, 4-angled, the angles are toothed, green and also reddish. Flowers are of curious shape usually arise from the base of the stem. |
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