Machaerocereus

Lemaireocereus ihurberi, commonly known as the organ pipe cactus, belongs to a group of Lemaireocerei with dark brown or even black felt in the arcoles. as opposed to the previous ones which all had light-coloured felt. It is also distinguished by having many more ribs, between twelve and seventeen in number, giving it a very different appearance from the other. In its wild state in Southern Arizona. Sonora and lower California it forms a large clump branching from the base, and this unusual branching habit persists even in pot-grown specimens making this an excellent addition to a collection and particularly suitable for show work. The numerous ribs are rather low and separated by narrow intervals with closely set areoles barely half an inch (1 cm) apart borne on the edges. The areoles become filled with a sort of waxy substance as the plants mature; this is quite natural and in no way detracts from the growth of the plant. It has numerous spines which practically cover the entire body of the plant.

Lophocereus scliollii is the only representative of its particular genus and. like Lemaireocereus ihurberi. it branches from Ihe base rather than from part of the way up the stem. The Greek name is derived from the word meaning a crest and alludes to the crop of bristles found on the flowering stems: however, this is unlikely to be a feature of pot-grown plants in this country as they require a warm sunny position. The stems of the plant form a large clump when mature with up to a hundred erect stems over 20 ft (6 m) in height. The ribs usually times there are as many as nine; they are separated from one another by broad intervals round the rather sickly looking greenish-yellow stems. The arcoles tend to be small with little or no felt in cultivated specimens and bearing up to seven short radial spines and two central ones. The dense bristles which have been mentioned as being produced only on the flowering stems of the plant, are very much longer and can be over 2 in (5 cm) in length. Some imported specimens may have these spines

This cactus grows in very dry areas of Western Mexico and Southern Arizona where it survives because of the dense clumps it forms which provide a little shade to conserve any moisture that is available. There is an unusual and handsome monsl-rose form in which the ribs have been completely superseded by large tubercles, and a form with fasciated growth is offered under the name of Cereus mickleyi. It should be kept on the dry side in cultivation.

Machaerocereus eruca, the creeping devil cactus, is an extremely impressive prostrate sprawling cactus whose stems bend over, root into the ground and then grow up again into the air. Because of this sprawling habit and because it is at any rate none loo common in cultivation il has not been illustrated here. The name is derived from the Greek for a dagger and is a particularly apt reference to the shape of the spines, which are very sharp. When cultivated it tends to be grown upright but it is able to pass over or round obstacles in its natural state where, because the base of the plant dies off with age and fresh roots are formed where the branches touch the soil, it gives the appearance of walking like a huge caterpillar across the desert. For the amaleur who wishes to have a representalive of this remarkable genus I recommend M.gummosus which does not sprawl around quite so much and whose initial stems are at least erect. It usually has eight ribs which are low and somewhat flattened and along the edges of which the areoles are borne nearly an inch (2-5 cm) apart. The stout spines are similar to those of M. eruca in thai the centre spine is flattened into a dagger shape in the middle of between eight and twelve radial spines.

The plant is common in lower California and is easily raised from seed. In spite of ihe fruit being a local delicacy ihe body of the plant is poisonous and the battered stems are thrown into streams by the natives in order to kill the fish.

Myrtillocactus

Monvillea

Myrtillocactus

Monvilleas are robust fast-growing species provided they are given plenty of sunshine of warmth in the winter as Lemaireocereus. There are about eight species of which only two are frequently offered commercially. The hardiest of these is undoubtedly Monvillea liaagei (sometimes referred to as haageana). This forms an erect or climbing shrub, occasionally needing staking as it becomes older. The stems are very slender, often less than an inch (2-5 cm) thick, and tinted purple. The best idea, if space permits. is to plant it out in the greenhouse and allow it to develop into a sort of thicket on its own. The shoots are surrounded by four to six prominently notched ribs and the areoles. which support a number of grey spines, are arranged in these notches at intervals of about an inch (2 5 cm). M. cavendishii is similar but has more ribs, sometimes up to ten in number, borne on greenish stems. The stems arc less deeply notched and the areoles are not so far apart, often less than half an inch (1 cm). It is comparatively free flowering, especially if planted out in borders in the greenhouse, and the white blooms are produced right through the summer in succession from April to September.

Monvillea insularis. although not commercially available, is interesting because it is the most easterly occurring cactus known. M. spegazzinii is sometimes offered as a grafted plant and is similar to M. liaagei but has the bluish stems heavily marbled with white: it is sometimes for this reason 112 sold as Cereus marmoralus.

vigorous and handsome cactus frequently and perhaps inadvisably used as grafting stock for species with less well-developed root systems. It has the advantage of forming pronounced branches even on quite young plants, and the stems, which are bluish green, develop bands with age showing where each year's growth has occurred. The stems carry live or six ribs, which on most cultivated specimens are so broad as to give the plant a sort of pentagonal-shaped stem. The areoles are just over an inch (2-5 cm) apart with a few short radial spines flattened against the sides of the stem. The central spines are very different being long, black and flattened and contribute greatly to the appeal of the plant. It is very common in Mexico where it is grown for its edible fruits known as garrambullas. These, if they are produced on your own specimens, should be left out in the sun to dry like raisins, which they look like and for which they can be safely used as a substitute.

Although this particular species is greatly valued as a grafting stock because of its vigorous growth, I cannot recommend it. Plants in cultivation tend to develop a hard scaly spot on the stems which I have been unable to associate with a pest or disease and which appears to do the plant no harm but renders it unsightly, It is possible that this brown marking, like that referred to in the section on opuntias. is brought on and encouraged by the cold damp winters in this country, and certainly growing the plants a little warmer at, say, 10°C (50°F)

seems to discourage these spots from appearing. It is a pity to spoil an otherwise impressive cristate specimen which has been grafted on to such a stock by allowing these spots to develop and the more experienced amateur is recommended to regraft on to a different species, such as Pachycereus pringlei illustrated on the

Myrtillocactus schenkii has dark olive-green stems and shorter central spines. The areoles are filled with blackish-brown fell and gel further apart as the plant grows older. M.cochal is another species occasionally found in shops which differs from both the preceding species in normally having no central spine at all.

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