How to take cuttings of cacti and pelargoniums

Press, 29 January 1988, Page 14

How to take cuttings of cacti and pelargoniums

lardenerSi! 8 DIARY

Derrick Rooney

Next month will be quite a good time to take cuttings from any cactus or other succulent that lends itself to propagation by this method — which in effect means just about every cactus and succulent except the globular, non-clustering South American ones. Convention dictates that cuttings of cacti and juicy succulents should be left lying with the cut ends exposed for a day or two, so that the wound can heal over. Some growers dip the cut ends in flowers of sulphur as an additional precaution against rot. Cuttings of cacti differ from those of conventional plants in that they need to be kept in a dryish atmosphere and need very little water until renewed growth indicates that roots have formed. Pumice seems to be the best rooting medium for them, and cacti love to grow in a potting mix that includes pumice, but in this part of the country pumice is expensive and hard to come by. Perlite is just about as good but is also expensive. Coarse gritty sand is adequate but gives a better root system if mixed with a little peat or leafmould. Cuttings of the more vigorous kinds may be ready for potting up by autumn, but most should be left alone until spring. Most of the cacti and some succulents will stand quite low temperatures if well ripened in autumn and kept dry in winter. Even the winter-growing crassulas and their relatives from South Africa need no more than protection from frost. Almost without exception, these plants are heat lovers and although many require protection from strong direct sunlight they need high summer tern-

peratures if they are to grow well. On the other hand, the so-called “orchid cacti,” or “lead cacti,” the species and hybrids of Epiphyllum, Zygocactus, and Rhipsalidopsis and their relatives, are forest or scrubland plants which require cooler temperatures in summer and will grow very well at that season in a shadehouse (no more than ,50 per cent shade, though). In winter they enjoy the sun and must be kept free from frost; though they will survive brief dips to or just below freezing temperatures, they may be badly marked. The convention with Epiphyllum cuttings is to take them about one-third of the way between the base and the widest part of the stem segment, but I don’t think this is essential. They are inclined to rot, though, if cut across the widest part of the stem. Cuttings of Zygocactus, the so-called Christmas cactus which flowers in winter, should include at least two segments. Pelargoniums Cuttings may also be taken in the next few weeks of zonal geraniums (which are really pelargoniums) — those wonderful tub plants which flower brilliantly throughout summer. Winter frosts knock “geraniums” about and often kill them, and it is a good idea to have a

few spares potted up in a frost-free place. Cuttings taken now, grown on in a glasshouse or sunny frame, and brought in to a sunny porch in late autumn should flower through the winter. In general the ivy-leaf types and the Regal pelargoniums require warmer conditions and are less cold-tolerant than the zonals. An aside here may preempt confusion over the use of the names “pelargonium” and “geranium.” In the strict sense, the Pelargoniums, known as storksbills, the Geraniums, known as cranesbills, and the Er odiums, known as heronsbills, and eight minor genera all belong to the botanical family Geraniaceae, which includes, worldwide, about 600 species, many of them weeds. Six

species, one of them, possibly two, worth cultivating, are native to New Zealand, and 18 are naturalised. The major difference between flowers of the three genera is that those of Pelargonium always have a nectary spur. The others have no spur. The spur is not always prominent, and sometimes is visible only as a small bump near the base of the flower stalk. Wild species of Pelargonium have flowers of irregular shape, usually with the two upper petals markedly smaller than the three lower ones, but this feature is not always apparent in the cultivated varieties, which have in many cases been selected for large, evenly-shaped flowers. Flowers of Geranium species have no spur, and

the five petals are of equal size. Erodium differs from Geranium in that its stamens have an outer ring of filaments without anthers (the pol-len-bearing bits). In Geranium all the filaments have anthers. The Geranium and Erodium species are hardy plants, whereas the Pelargonium group tend to be frost tender. Zonal pelargoniums — the garden “geraniums” — are so called because the South African species from which they were developed has a dark band on the leaf. This feature is exaggerated in some of the “colouredleaf” varieties, such as “Distinction” and “Marechal MacMahon.” To wilt or not to wilt? Older garden books, incidentally, will advise you to “wilt” cuttings of "geraniums” by leaving them-to lie on the bench for a day before planting, the theory being that this allowed the fleshy stems time 'to heal where cut and reduced the risk of foot-rot. Many people still with geranium cuttings and it doesn’t seem to do much actual harm, in that the cuttings usually seem to grow in spite of it. But there is no reliable experimental evidence that it does any good. I don’t know of any commercial grower who wilts geranium cuttings. Gritty sand was the traditional rooting medium, but as with the succulents, a mixture with peat or pumice or perlite will give better results. I known one commercial grower who roots all his cuttings directly into the pots and potting mix in which they are to grow.