Epiphytic Cacti – a personal view of the taxonomy and cultivation

Text and photos by Alan Tuppen (BCSS Harrow Branch)

For most cactophiles, epiphytic cacti are represented by three genera: Epiphyllum, Schlumbergera and Rhipsalis. And these three genera are represented by cultivars of Epiphyllum anguliger and E. gertrudianum, Schlumbergera truncata and S. gaertneri, and various predominantly shrubby Rhipsalis, such as R. baccifera, R. paradoxa and R. capilliformis. The large-flowered Epiphyllum hybrids are seldom seen, except by enthusiasts, but their flowers can be truly spectacular: up to 25cm across and in a great range of colours except for blue (the Cactaceae family doesn't carry the genes for blue colouring). They are not difficult to grow but need a lot of space, can be ungainly, and have a limited number of flowers each year. In fact, many of them have little Epiphyllum ancestry, being mainly Disocactus and Selenicereus, especially in the USA where hybridisation continues unabated.

Epiphyllum

A small number of Epiphyllum species are available and are desirable for their distinctive growth forms and their large, predominantly white and strongly scented flowers that last for only one night, except for E. crenatum, which has diurnal flowers. E. oxypetalum (Fig. 1) has the largest flowers in the genus, measuring up to 18cm across, with a distinctive swan-necked tube and a scent that hits you as you enter the room. Some Epiphyllum enthusiasts have been known to hold "moonflower parties" and, as dusk falls, the flower starts to open until, before long, it is wide open and its scent fills the room. The plant itself can be very ungainly, with smooth, wavy-edged, flat stems, from which flowers and other stems grow - not from a central point. They also send out long, thin "streamers" from which, eventually, other stems grow, forming a satellite plant, a feature found also in some Rhipsalis. Plants can become very large. E. crenatum has stems with scalloped edges, while those of E. anguliger and E. gertrudianum have zigzag edges (Rick-Rack cactus). On E. gertrudianum the lobes are rounded. E. anguliger is sometimes confused with Cryptocereus anthonianus, which can be an epiphyte or a scrambling or climbing lithophyte with red and cream narrow-petalled flowers that are not easily produced. All of these are tender plants, including the Cryptocereus, and should be kept above 10°C in winter. As a result of recent DNA analysis, E. crenatum, anguliger and gertrudianum have been reassigned to Disocactus (see below) but are still sold as Epiphyllum.

Fig. 1 Epiphyllum oxypetalum

Fig. 2 Epiphyllum gertrudianum

Schlumbergera

Everyone will be familiar with the Crab Cactus, Schlumbergera truncata, produced in their millions in a variety of colours for the Christmas market each year, with their zygomorphic flowers. S. gaertneri, is also produced in large numbers for the Easter market, mostly with regular, red flowers.  Less well-known are S. rosea, with small segments that colour up nicely in the sun, and have dark pink, regular flowers. S. opuntioides (Fig. 4) has segments that resemble small Opuntia pads with weak spines (no glochids!) and pink, zygomorphic flowers like those of S. truncata but these are much more reluctant to flower.  A plant that used to be common but is now seldom seen is S. x buckleyi (Fig. 3), the original Christmas Cactus, with flat, regular segments and pendant, tiered, fuchsia-pink flowers.  Also very attractive is S. x graeseri, with bristly segments and regular, dark pink flowers that have a violet tinge.  Apart from these two hybrid plants, all the Schlumbergeras I have grown tend to drop branches or suddenly disintegrate if conditions aren't right.  Re-rooting the resulting bits is tedious but usually not too difficult.

Fig. 3 Schlumbergera x buckleyi

Fig. 4 Schlumbergera opuntioides

Rhipsalis

Various species of both pendant and shrubby types of Rhipsalis are commonly sold as houseplants.  It is a large genus of around forty species, and includes the only cactus species to occur naturally outside the New World.  Rhipsalis species have mostly cylindrical pendant stems and branch frequently. Many have very small flowers followed by smooth berries and are known as Mistletoe Cactus.  Plants to look out for are R. paradoxa, Chain Cactus, on account of the alternatingly angled profile of its stems, R. pachyptera with wide, flattened segments, and R. elliptica (Fig. 5), with its spear-shaped flat segments that colour attractively in bright light.

Fig. 5 Rhipsalis elliptica

Fig. 6 Rhipsalis capilliformis

In addition to the three aforementioned genera, Disocactus and Lepismium deserve special mention.

Disocactus

The genus Disocactus has been the recipient of plants from various genera, so that Aporocactus flagelliformis (Rat's tail cactus), Epiphyllum ackermannii, Nopalxochia phyllanthoides (Deutsche Kaiserin) and Heliocereus speciosus are all now species within Disocactus.  D. ackermannii (Fig. 7) and D. phyllanthoides (Fig. 9) both have flat stems similar to Epiphyllum, while D. flagelliformis has thin, multi-ribbed stems and D. speciosus has spiny mostly four-angled stems.  In this genus stems grow from a central point, making them tidier from a collector’s point of view.  Disocactus are also more tolerant of lower temperatures.  D. phyllanthoides has pink flowers that are smallish and don't open fully but are produced in large numbers, while D. ackermannii has large, red, wide-opening flowers and stems that are often unevenly scalloped.  Other species to look out for are D. biformis, D. eichlamii and D. nelsonii, which has pink trumpet-shaped flowers.

Fig. 7 Disocactus ackermannii

Fig. 8 Unnamed Disocactus hybrid

Fig. 9 Disocactus phyllanthoides

Lepismium

Similar to Disocactus, Lepismium has received species from Pfeiffera and Rhipsalis.  The species most commonly found are: L. bolivianum, which has become commonly offered as a houseplant, with narrow, pendant, spineless stems and small flowers; L. ianothele, with four-angled spiny stems and white flowers; L. monacanthum, with smaller growing, weakly-spined flat stems and small orange flowers; and L. cruciforme (Fig. 10), with flat or three angled stems and small pink flowers.  Also worthwhile is L. houlletianum (Fig. 11), which is quite tolerant of low temperatures and has long, spineless, saw-toothed stems which are attractively bloomed when young.  The flowers are small and cream-coloured but produced in large numbers and two or three times a year.

Fig. 10 Lepismium cruciforme    

Fig. 11 Lepismium houlletianum

Fig. 2 Pachyphytum oviferum

Fig. 3 Graptopetalum bellum

Fig. 4 Graptopetalum macdougallii            

Fig. 5 Graptopetalum macdougallii flowers

Also, there is Graptopetalum suaveolens (Sedum suaveolens to me and many others). A spectacular plant whatever you wish to call it. See Fig. 6.

Fig. 6 Graptopetalum suaveolens

Graptoverias (Graptopetalum x Echeveria), are even more numerous than graptosedums and are represented by well-known ones such as ‘Acaulis’ (G. paraguayense x E. amoena?), ‘Bronze’ (G. paraguayense x E. stahlii?), ‘Douglas Huth’ (G. paraguayense x E. gigantea?), ‘Amethorum’ (E. purpusorum x G. amethystinum), ‘Fred Ives’ (G. paraguayense x E. gibbiflora(hort)), ‘Iona’ (G. filiferum x E. setosa subsp. setosa?), ‘Opalina’ (E. colorata f. colorata x G. amethystinum), ‘Royal Flush’ (G. amethystinum x E. affinis), ‘Silver Star’ (G. filiferum x E. agavoides ‘Multifida’?), ‘Titubans’ (G. paraguayense x E. derenbergii). These are all well worth searching out as they have interesting parentage. There are many more, some very rare now and almost unheard of or perhaps given new names.  There is a cross between G. bellum and G. suaveolens (Sedum suaveolens) called Graptopetalum x ‘Altair’ (Fig. 7). I have yet to have it flower.

Fig. 7 Graptopetalum x ‘Altair’

There are also some very obscure hybrids that are difficult or impossible to track down. ‘Alfred Waltemyer’, a probable hybrid among Echeveria, Graptopetalum and Pachyphytum having characteristics of all three. ‘Terita’, a hybrid between a Graptophytum and a hybrid Echeveria. ‘Glow of Peony’ is an interesting yellow hybrid between a Graptoveria and a Graptosedum. There are doubtless others, as new hybrids are being produced all the time. I would expect some to look almost identical to others, as reproducing a genuine hybrid gets more difficult as time moves on.

Many graptopetalums grow on cliff edges and mountainsides, and are remarkably hardy, if not fully hardy. This is a valuable clue to their growing requirements. They need very good drainage and some shade, so I grow them in a very gritty mix and give them plenty of water in summer but none in winter; they stay dry in the greenhouse, which is kept cool. It’s worth testing some spares outside in winter in the interest of science and knowledge. I have done this and, in mild winters as long as they stay dry, the tougher ones, such as graptoverias ‘Fred Ives’ and ‘Douglas Huth’ are fine. They should be fine if they are dry: outside but under shelter. If the temperature falls below -5°C I would be sure to bring them into slightly warmer surroundings. In spring most of them are grown outside as they are robust plants and benefit hugely from the wind, rain and sun – even that of the northwest UK. Their colours develop and change considerably from their winter condition and they flower well.

Fig. 8 Graptopetalum paraguayense

Given the small number of graptopetalum species, you would not expect there to be so many hybrids to choose from and explore. Their ability to hybridise with echeverias, sedums and pachyphytums renders this expectation invalid. There are hundreds of hybrids and many shapes and sizes and colours; to own them all would be near impossible. However, it is an interesting exercise to try to identify the parents by just looking at them; you may surprise yourself with how much you learn by doing this, even if you are not so successful.

Fig. 9 Graptoveria 'Douglas Huth' grown in shade

Fig. 10 Graptoveria 'Douglas Huth' grown in sun

Graptopetalums are underrated plants, that are worthy of another look, just like sedums. They are varied, hybridise very well, are almost fully hardy and well worth growing if you like the Crassulaceae succulents and want to study the variation within the species and parentage of the hybrids.  Many people grow echeverias, justifiably, for the variety and interest of their form and the long-lasting beauty of their flowers. Graptopetalums have the same qualities but with far fewer species.

Fig. 11 Graptoveria 'Iona'

Succulents on Stamps, Part 5

Text and photos: Les Pearcy

This month I will look at an issue from Peru dating back to 1989 and featuring native cacti. There were five stamps in the set and they all feature an image of the plant in flower.

Corryocactus huincoensis was described by Friedrich Ritter in 1981. The plants form long thin stems up to 2m in length and have yellow flowers about 6cm wide.

Fig. 1 Corryocactus huincoensis

Loxanthocereus acanthurus is now referred to as Cleistocactus acanthurus. It has stems about 50cm in length and scarlet flowers about 5cm in length.

Fig. 2 Loxanthocereus acanthurus

Haageocereus clavispinus forms spiny stems up to 1m in height with white flowers about 6–7cm in length. 

Fig. 3 Haageocereus clavispinus

Matucana cereoides, as the name suggests, form columnar stems up to 50cm in length. It is now known as M. haynei. 

Fig. 4 Matucana cereoides

Trichocereus peruvianus is a large growing plant with stems up to 7m in length and produces large white flowers typical of the group. This is another plant now known under a different name; all members of the genus have been transferred to the Echinopsis genus.

Fig. 5 Trichocereus peruvianus

Above: Figs. 2, 3 and 4  I took an enjoyable stroll around the gardens today…

Well, the rain has yet to materialise!  Thank goodness we have sufficient land to qualify for the life-saving irrigation water. Otherwise, we’d have to use tap water!  However, because of the water shortage, the irrigation water is now being mixed with desalinated water which, according to my farming friends, will spell disaster in the long run as desalinated water lacks certain minerals, many of which are essential for plant growth and health.  It’s a wait-and-see situation but worrying for growers of every type of plant (never mind human usage).

As growers, we are always on the lookout for pests that are intent on destroying our collections.  One of the favourite genera in my collection is the Aloe and this year, for the first time ever, they are being decimated by the dreaded aloe mite. It is so disheartening to see clumps of distorted stems, leaves and flowers appearing almost everywhere I look (see Fig. 5).  In an attempt to curb the problem, I cut out and burn the affected parts and try various chemicals. I shall keep at it! 

Below: 

Fig. 5 Aloe plant affected by aloe mite