Rhipsalidopsis

The nexi two pages illustrate a second group of epiphytic cacti called the Rhipsalidanae. The type genus is Rliipsalis and the botanical name is derived from the Greek word for wickerwork and is an allusion to the generally interlocking appearance of the branches of the plants. The group was one of the earliest ones to spread out of America and many of the species which are grown require rather warmer, more humid conditions than other cacti if they are to thrive. For this reason some of the less commonly available species are best left to those with a greenhouse where the minimum winter temperature can be maintained at 13°C (55°F) with a relatively high level of humidity. During the summer, too, they will need special treatment in the form of protection from direct sunlight, and since this conflicts with the requirements of the desert cacti it is seldom possible to grow the two families together in the same environment. The root systems are very scanty and the plants hardly need pots. If facilities are available they wiH do well when mossed on to an upright stump, although extra care must be taken with the watering under these circumstances as they will dry out quite quickly. Orchid compost makes an excellent rooting medium but if this is not available then a mixture of peat, cork, leaf-mould, sphagnum moss or anything else which is spongy in texture and organic in origin will serve as a medium.

Like zygocactus. rhipsalis arc generally winter flowering although the growth is made during the summer and a short rest for some six weeks during which water should be given sparingly is normally advisable towards the end of September.

Hariota salicornioides has been given the somewhat unkind name of drunkard's dream since the stem segments are faintly reminiscent of bottles. It makes a good house plant and is considerably more tolerant of adverse conditions than the rest of the group. The plant is frequently sold as hatiora and forms a bushy clump often producing a long main stem but otherwise branching frequently to form a densely knit mass of pale green bottle-shaped joints. The spines are very short and bristly and are hardly noticeable on the plant and the small yellowish-green flowers are produced at the ends of the short-jointed branches during late December or early January. Consequently it needs some warmth and water during this period. It is a somewhat uncertain flowerer unless grown in a warm greenhouse although its curious stems make it an unusual addition to the collection.

Rhipsalidopsis rosea is frequently confused both with Schlumbergera gaertneri, with which it has been hybridized of late, and with Zygocactus truncatus and it is often somewhat misleadingly sold as the latter under the general English name of Christmas cactus. It is a somewhat delicate plant shedding its stem segments easily when allowed to get too dry, too wet or too bright. Although a rewarding flowerer it is advisable for this reason to strike cuttings as the opportunity arises to guard against the possible loss of a valued plant. It differs mainly from rhipsalis in having considerably larger, more showy flowers and forms a freely branching ultimately pendulous plant which does well when grafted on to a taller stock. The stem segments themselves are somewhat variable, some of them are flat jointed while others are broadly triangular in section. Both kinds are normally produced on the same plant and the margins of the segments are often tinged purple. Although this does not inevitably mean that they are getting too much light you should suspect it and lake the necessary precautions especially where it happens during summer. The flowers are produced at the apices of the terminal segments during the late spring and early summer and although not as long lasting as rhipsalis are nevertheless longer lasting than those of most other cacti. The pale purple blooms are extremely attractive and make this a very worthwhile addition to the collection in spite of its somewhat delicate nature.

Rhipsalidanae Cactus
Rhipsalis

Mosi rhipsalis have angled or cylindrical stems at least over part of the plant. Rhipsalis houlleliana is an exception to this in having flat, rather graceful stems with a prominent mid-rib and a conspicuously serrated margin. This edge can become reddish with full sunlight or with drought. The flowers are quite conspicu6us for a Rhipsalis species and are followed by red berries, the flowers themselves being cream with reddish centres and somewhat bell shaped.

There are several other species of Rhipsalis with flattened stems, those of R.pachypleru are rather fatter than the illustrated species and the lower segments are often somewhat angled. The flowers are yellow, frequently with a trace of red, and the m e fruits

•salis cc white fruits which resembles R. houlleliana. and R. warmingiana lacks the prominent mid-rib of the illustrated species but has scented white flowers and black fruits.

name suggests, highly reminiscent of a mesembryanthemum. It is at first sight rather similar to Harioia salicornioides illustrated on the previous page but differs from that species in being considerably more bristly.

Although R. mesembryanthemoides is fairly distinctive in appearance, there are several other species of Rhipsalis which are characterized by short rather bristly joints. These include R. capilliformis. R.lielero-clada and R.cassullia. which has already been mentioned as being the most easterly growing of all the true cacti. R.prismaiica is also somewhat similar in appearance but the upper branches arc distinctively angled, giving it its specific name.

Rhipsalis paradoxa is typical of a group of rhipsalis with prominently angled stems, the distinctive feature of this plant being the way in which the wings of one joint are produced opposite the flattened parts of the previous joint, giving it its name. In habit it is a pendulous plant which branches at the tips although this does not necessarily occur every year. The stems are generally three angled and vary in length, some being stubby, others being up to a foot (30 cm), normally pale green in colour but often acquiring a reddish tinge, especially when exposed to direct sunlight or when allowed to suffer from prolonged periods of drought. It is one of the hardier species mentioned so far. its thicker stems and greater degree of succulence enabling it to tolerate adverse conditions such as cold, lack of humidity and drought more effectively than the less succulent species already mentioned.

Although all Rhipsalis have areoles, the distinctive feature of the cactus family. R. paradoxa has very inconspicuous ones. The bristly spines are normally only found on the younger areoles which also have a certain amount of wool in them. Flowering is somewhat erratic and only older plants can be relied on to produce flowers at all. They are carried at the tips of the joints

Various other winged or ribbed Rhipsalis are common in collections; R.gonocarpa is distinguished by black fruits, and R. irigona by reddish fruits. R. tonduzii. which is a native of Costa Rica, differs in having four-

As with most epiphytic species Rhipsalis may be grafted with good effect. Generally it is better to use stouter grafting stock such as Trichocereus as the plants make quite large and fairly heavy specimens with time. They are not generally suitable for the with it would probably be R. paradoxa. which although one of the harder ones to flower is generally easier to keep alive.

______, __ r. the end and allow the latex or milky sap to dry naturally and form a protective surround to the wound.

is an extremely poisonous inhabitant of Africa although it has become naturalized in part of eastern India. It is aptly described as the stick plant and ultimately attains a considerable height. It is comparatively swift growing especially when cared for in a greenhouse and is almost impossible to kill. The branches arc repeatedly forked and produce small leaflets at the sides and tips of the young ones although these fall off with age. There is a somewhat similar species - E. iniisyi - from which India rubber is made. The latter is an inhabitant of Madagascar and forms a sort of brownish bark on the sunny side of the stem in its native state. The main difference between the two species lies in the slight protuberances on the sides of the stems of the latter species from which the leaves are produced. It is possible that some confusion between the two species has occurred

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