Correct Soil mixtures for succulents

The adaptable succulents can be grown in almost any sort of soil so long as it is porous and properly drained; but a well-balanced mixture will, other things being equal, give better results – steady growth, regular flowering, freedom from disease.

Though a large number of recipes can be found in older books, modern experience shows that John lnnes Potting Compost No. I is as good for most succulents as it is for other plants, preferably adapted by adding I part of some gritty material — coarse sand, road grit, small brick or pot chips, or vermiculite — to every 4 parts made-up compost. Ready-mixed composts modified in this way can be bought. Really strong-growing plants such as aloes, agaves, opuntias, cereus, can go into John Innes No. 2 or No. 3 mixtures, which contain more fertiliser.

South African succulents, such as lithops, conophvtum etc., need more sandy compost without fertiliser: a suitable mix is 2 parts loam, 2 parts coarse sand and 1 part peat. Jungle cacti — epiphyllum, schlumbergera etc. — like much richer compost, say 2 parts loam, 1 part coarse sand, and 1 part leafmould, spent mushroom compost, or peat, adding 3 oz. Hoof and horn meal, 3 oz. Superphosphate and 1^ oz. Sulphate of potash per bushel.

If making up your own compost, avoid any organic material that is still decomposing, like insufficiently rotted manure or compost. Loam should be medium to heavy, without too much fibre – except for the jungle cacti -and should if possible be sterilised.

Potting

Succulents need repotting like any other plants, and those that grow rapidly will fill a pot with roots in a year. The most frequent causes of collapse are allowing plants to become so root-bound that there is insufficient food in the soil, and clogged drainage, both of which are averted by regular repotting.

As for any plant, pots and crocks should be clean and sterile. The best time to repot most cacti is between March and May; other plants as soon as signs of renewed growth are seen, and preferably when the outside temperature is at least 13°C. (55° F.). Succulents can be repotted at any time, so long as there is active growth, and if a plant is doing badly the first thing to do is to look at the roots.

Young and vigorous plants may need annual potting, and others are best repotted every two or three years. Slow growers with poor root systems may be left longer. Before repotting, the soil should be fairly dry. With some plants the orthodox method of turning out of the pot may be used, holding the stem in one hand, the pot upside down and tapping the rim on the edge of the bench or staging. As so many succulents are brittle, it may be safer to push the root ball up with a finger or stick through the drainage hole. Holding the plant is not always easy: small, soft plants must be held very gently, and with spiny ones leather gloves should be worn or the stem held in a pair of padded tongs. Alternatively, a strip of newspaper, folded over and over and passed round the plant, is handy.

Once the plant is out of its pot, some of the old soil can be picked away, using a pointed stick if necessary, and a look-out kept for various pests. Be careful not to pull away too many of the fine root-hairs. Dead or broken roots should be cut back to living tissue with a razor-blade or very sharp knife. Cut surfaces are best dusted with sulphur or charcoal dust. Any decay on the plant should be dealt with when repotting; also clean off dead leaves, dry skin, etc.

The new pot should accommodate the roots easily, with a little room to spare. If the plant is large but the roots are limited, a shallow pan is desirable, or the result may be top-heavy. Conversely, a plant with a long tap-root, like many cacti, needs a long narrow pot.

Crocks should cover the hole, but a deep layer is not usually necessary. A layer of stone chips can be placed over this. There is no need to overdo the drainage: all that is required is to ensure that excess water should be able to run out freely, without any danger of keeping the soil wet and stagnant.

The plant should be replaced so that the soil comes up to the original level. Hold it in position and let the fresh soil trickle in round the roots, tapping the pot on the bench to shake it down, and if necessary pushing the soil in with a stick. The soil should be firm but not rammed down, and come up to about 2 in. below the pot rim. A layer of small stone chips on the surface will prevent the soil caking or becoming compressed.

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