History of cacti in South Africa

On our website you can find a brief history of cacti in South Africa. Last night we received a nice addition from the USA:

The restablishment of the Soekershof garden after many years of
neglect is fantastic — the photos were fantastic.  Here is what I
have in my records for Marthinus Malherbe:

Malherbe, Marthinus [Maarten] (1885-1976); RSA nurseryman & amateur
botanist; creator & owner of Sheilam Cactus Gardens nursery in
Robertson, RSA on and after 1936; designed succ garden at Soekershof
Walkabout 1965; explored & collected in RSA; introduced cacti &
other Amer succ in RSA 1910; spouse Molly [nee Darling] Malherbe
( -1994);

Nananthus (Aloinopsis) malherbei was named after him and he
discovered Haworthia comptoniana, now Haworthia emelyae var
comptoniana
.”

In addition to this: The name SHEILAM is an abbreviation of the names of his children. During the first 15 years the nursery was named SHEILA and the M was added in 1951 when his (second) wife gave birth to their daughter Marsha.

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A succulent roof garden

Recently Soekershof Walkabout, Private Mazes & Botanical Gardens in South Africa, welcomed two lovely guests from Maryland, USA; Edmund Snodgrass and his wife Lucie.

This couple is the author of the book ‘Green Roof Plants’ (ISBN 978-0-88192-787-0). It includes photographs and cultural information about more than 200 species and cultivars including data about heat tolerance, moisture needs, hardiness and so on.

This practical handbook is a valuable resource for anyone interested in the subject and covers it all; from roof construction and plant selection to soil medium and maintenance.

In combination with solar (photo-voltaïc) energy a roof garden with its insulating qualities can, especially with the South African power outages, contribute to significant less dependence of public electricity supply and less energy use for cooling (in Summer) and heating (in winter).

The book can be ordered in any ordinary bookshop or, online, via Amazon.

The blogsite of Urban Habitats is also a useful source for people who want to know more about roof gardens.

Another useful blog is that of Durban based landscaper Ross Nevette.

Recommendation for US-readers

ken-and-deena-altman.jpgFor the American readers of this blog we can recommend the website of Altman Plants in Vista CA. Ken & Deena Altman visited us today and they are impressed but our ‘operation’ is small in comparison with theirs: 800 acres on 3 locations in Florida and California of which 290 acres with succulents. And their website is the most informative of all US-nursery websites we’ve seen with pop-ups which describes (with pictures) the different plants. Their prices are, within the USA, very competitive.

What started as a small backyard operation in LA in 1975 has grown into a huge well organised nursery.

Cactaceae

Recently we submitted a more general article about succulents. this time a bit more about cactaceae

Cactus is the name given to any member of the flowering plant family Cactaceae. Cacti are almost exclusively New world plants. This means that they are native only in the Americas and West Indies. There is however one exception, Rhipsalis baccifera; this species has a pantropical distribution, occurring in the Old World in tropical Africa, Madagascar and Shri Lanka as well as in tropical America. This plant is thought to be a relatively recent colonist in the Old World (within the last few thousand years), probably carried as seeds in the digestive tracts of migratory birds. Many other cacti have become naturalized to similar environments in other parts of the world after being introduced by people.

Many species of cactus have long, sharp spikes.Many succulent plants in both the Old and New World bear a striking resemblance to cacti, and are often called “cactus” in common usage. This is, however, due to parallel evolution; none of these are closely related to the Cactaceae. One distinct identifying characteric of the Cactus family is the areole, a specialized structure from which spines and new shoots grow.

Cacti are believed to have evolved in the last 30 to 40 million years. Long ago, the Americas were joined to the other continents, but separated due to continental drift. Unique species in the New World must have developed after the continents had moved apart. Significant distance between the continents was only achieved around in the last 50 million years. This may explain why cacti are so rare in Africa; the continents had already separated when cacti evolved.

Cactus Flower

Like other succulents, cacti are well-adapted to life with little precipitation. The leaves have evolved into spines, which in addition to allowing less water to evaporate than regular leaves, defend the cactus against water-seeking animals. Photosynthesis is carried out by enlarged stems , which also store water. Unlike many other succulents, the stem is the only part of a true cactus where this takes place. Very few members of the family have leaves, and when present these are usually rudimentary and soon fall off; they are typically awl-shaped and only 1-3 mm long. Two genera, Pereskia and Pereskiopsis, do however retain large, non-succulent leaves 5-25 cm long, and also non-succulent stems; they are possibly primitive genera, thought to be closely similar to the plants that cacti evolved from.

Cacti come in a wide range of shapes and sizes. Some grow to great size. Some cacti produce beautiful flowers , which like spines and branches arise from areoles. Many cactus species are night-blooming, as they are pollinated by nocturnal insects or small animals, principally noths and bats.  Cacti range from small and round to pole-like and tall, such as the Saguaro

A number of cactus species are cultivated for use as houseplants, as well as for ornamental gardens. They often form part of xerophylic (dry) gardens in arid regions. Some cacti bear edible fruit.

 

Etymology

The word cactus is ultimately derived from Greek Κακτος kaktos, used in classical Greek for a species of spiny thistle, possibly the cardoon , and used as a generic name, Cactus, by Linnaeus in 1753 (now rejected in favor of Mammillaria). There is some dispute as to the proper plural form of the word; as a Greek loan into English, the correct plural in English would be “cactuses”. However, as a word in Botanical (as distinct from Classical Latin) “cactus” would follow standard Latin rules for pluralization and become “cacti”, which has become the prevalent usage in English.

 

One of the largest cactus (and other succulents) collection in the unprotected open air (NOT under cover of a roof or shade net) can be found at Soekershof Walkabout in South Africa.

 

This article is an extract from Brainyenceclopedia

 

Asclepiads

This group of highly succulent, more or less leafless plants belongs to the family Apocynaceae. Found exclusively in the Old World, they are widely distributed over the drier parts from the Southern-most tip of Africa to the southern shores of Europe and eastwards to Arabia, India and Myanmar. Of the roughly 330 known species, 182 occur in Southern Africa, and all but a handful of these are endemic to this region.

Asclepiadaceae is a plant family which differs from others by having a very complex sexual apparatus and a complicated pollination procedure. They are easyly recognisable by five-lobed flowers. The lobes are joined together at the base of flower (corolla).

There are about 2000 species of Asclepiadaceae split into some 300 genera, of which about half are succulent. The succulent ones are of interest, especially the group named stapeliads. Their flowers are miraculous. I have read somewhere:  “Orchids of the Succulent world”/   The flowers of stapeliads have one flaw only. Most of them don’t have a pleasant smell.

Asclepiads grow worldwide, from jungles of Indonesia to deserts and steppes of Africa while stapeliads grow only in the old world. There are some representatives in Europe, too, in Southern Italy and Spain. Most of them are from dry regions of South, East and North Africa, Arabian peninsula and some even from India, Sri Lanka, Myanmar (Burma) and Nepal.

Most Asclepiads enjoy warm conditions, and appreciate regular application of water  in hot Summer weather providing that the plants are in their growth phase. For some of the more difficult Asclepiads, heat is a requirement and watering should be more circumspect. At Soekershof Walkabout we always use rain water, and tend to water over the top of most plants – after all that is how it happens in habitat. However, many growers prefer to water plants from the bottom (simulating drier conditions where the roots seek underground moisture), and a careful approach to watering is essential for difficult or rare plants.  It is a good idea to allow the soil to dry out between waterings, and if the weather goes cold in the middle of the summer, then stop watering. Much of the reputation that Asclepiads have for rotting unexpectedly is probably related to watering plants too early in the year while still dormant, or when the weather is uncertain, or to attack by other pests such as root mealy bug, the damage from which allows disease into the tissues. Indoors Asclepiads seem to do best in very free-draining gritty compost  which helps the compost to dry out between watering. Peat-based composts, with lots of sharp sand and fine grit works well, but peat also encourages root-mealy bug.Always remove dead plant material (dead flowers, leaves, stems) from your growing space, as otherwise in damp weather it will become colonised by fungi and rapidly become a source of spores, which may in turn infect your asclepiads.

If a plant that was growing well suddenly goes into a decline, suspect root-mealy bug. This pest destroys the roots, preventing proper uptake of water, so the plant looks under-watered even though it is sitting on soggy compost. Probably the damage also helps fungi to enter the tissues, and the next stage is a rotten plant.
Ordinary mealy bugs are also a major problem with Asclepiads, and are difficult to eliminate from crevices between the stems. Mealy bugs can be spread through a collection by the wandering vegetative growth of tuber-forming Ceropegias. Scale insects are said to be a major pest of Asclepiads in some climates.
It is a good idea to take cuttings from suspect plants that are not thriving, clean off obvious infestation and start off some new plants in case the original can not be saved. 

 Here we replant most of the asclepiads (especially Stapelia-species) every one of two years on a new location. This also prevents rot caused by soil related fungi, etc.

 

Propagation

Many Asclepiads are readily grown from seed, and some people grow plants of the faster growing species to flowering size from seed each year, thus avoiding problems of overwintering. However, the seed of many species (e.g. Stapelia sp.) has a limited life expectancy, and should be sown fresh. Those species with fleshy stems are easily propagated from portions of the plant laid flat on a gritty potting mixture, when they will produce roots from the underside of the stems. Planting stem cuttings vertically seems generally less successful (an exception is the vine-like Ceropegia species e.g. C. radicans), and the portion of plant embedded in the compost is prone to rot rather than root. Tuber-forming Cereopegias can be propagated from small tubers formed at joints in the thin stems. Regular propagation of plants with a few cuttings seems to be the best insurance against loss of the main plant.

  Internet literature:

 Stapeliads 

Pollination 

Articles about stapeliads 

Grafting stapeliads

 Ceropegias:  

 

About Crassulaceae

The Crassulaceae or orpine family consists of 33 genera with a total of around 1400 species. These dicotyledons have the characteristic that they store water in their leaves. Most species are native to Southern Africa and the Northern Hemnisphere.

Another characteristic of this family is that the different species hybridise easily. Advised propagation is (leaf-)cuttings but for gardeners who like to experiment with cross pollination the crassulaceae are very rewarding.

All crassulaceae originate from areas where water is (sometimes) scarce.

In the Western Cape: no additional water in Winter but during long dry spells in Summer Crassulaceae will reward you with extra growth if you give them a good morning soak once every week.

Tip: cut flowerheads out of young plants. This will stimulate growth and spread.

Soil: In general Crassulaceae are not fuzzy about soil as long as it drains and the pH is somewhere between 6.5 and 8. They even grow in heavy clay but too much clay has the disadvantage that after heavy rainfall followed by high temperatures there is a risk of rot.

Pest and diseases: Most common are aphids which are a real pest for some Crassulaceae. Aphids can become a plaque during high temperatures after rainfall.

Crassulaceae originate from areas with a wide scope of temperature-zones (USDA 6-10/11) but most from (sub-)tropical climates.

In South Africa we experience regulary that overseas Crassulaceae like the ones blonging to the genera of Aeonium and Echeveria are sold as “indigenous” by nurseries. Maybe because some of the species of these genera are common in many South African gardens.

Some of the more common known, except the ones mentioned, genera of the Crassulaceae are:

Dudleya; Sempervivum; Sedum; Tylecodon; Cotyledon; Andromischus; Monanthes and Kalanchoe.

Three of our favorite Crassulaceae:

Kalanchoe marmorata: Originate from Ethiopia, Sudan, Kenia. This Kalanchoe has paddle-shaped blue-green leaves with purple markings. Attractive in any rockery of succulent garden. Large white pinwheel flowers in clumps. Easily to propagate with (leaf-)cuttings.

Crassula columnaris (“koesnaatjie“): This monocarpic dwarf (Western and Northern Cape) needs at least 5 years to mature and becomes 5 cm high. When mature it starts to flower. It can grow in full sun in well drained (slightly alkaline) soil. The plant will tell you when it needs water (shriveling leaves). The scent of the flower is divine. Propagation by seed or leaf-cuttings.

Kalanchoe orgyalis: This native from Madagascar is relatively rare in cultivation. This Kalanchoe has thick velvet-like leaves which makes it sensitive in climates with a high humidity. The leaves are silver toned mahogany coloured. The flowers are bright yellow. This specie becomes about 50 cm high but that can take a while. Kalanchoe orgyalis is very, very slow growing in comparison with the other species of this genus.

About Aloes

The genus name Aloe is derived from the Arabic, alloch and translated as allal in Greek and Hebrew, literally meaning bitter or bitter sap which is descriptive of Aloe sap. The genus Aloe belong to the family Asphodelaceae to which also other succulent genera such as Haworthia and Gasteria. A widely spread misunderstanding is that also the Agave and related American genera belong to the same famly. These belong to the family of the Agavaceae. Some Aloe species (f.e. A. Ferox, A. Barbados and A. Socotrine) are valued for their medical properties. There is however a large number of medical claims which are not scientifically proven up to date or are proven to be false. The globally best known Aloe is the Aloe barbadensis (better known under the previous botanical name Aloe vera). The Aloe barbadensis is commercially cultivated in the USA, Australia and India. In Maharashtra, Madhya Pradesh, and Gujarat, India, Aloe vera is raised as an organic. The crop is ready for harvest after 18 months from sowing. The average yield for organically grown aloe is approximately 12 t/ha. 

 Soil

A slightly alkaline (up to pH 8.5) sandy loam soil is the  most ideal for most Aloes but some prefer slight acidic soil (pH 5.5-6.5) such as A. mitriformis (A. perfoliata) and A. plicatilis. It is normally propagated through root suckers or by cuttings of the new growth. Because Aloe plants consist of 95% water, they are extremely frost tender. If they are grown outdoors in warm climates, they should be planted in full sun, or light shade. The soil should be moderately fertile, and fast draining. Established plants will survive a drought quite well, but for the benefit of the plant, water should be provided. 

Pests:

All known garden pests can be kept to a minimum by simply ensuring optimal growing conditions and a good selection of plants that attract wildlife to your garden. In principle a garden is always un-natural. One of the challenges of organic gardening is to make use of nature in order to strive towards an ecological balance. For our and your dissapointment: even nature is never in balance. There are many ‘surprises’ every year but without ‘ecological measurements’ these can go a bit out of control. A daily ‘inspection’ walk in the garden -preferable early morning or late afternoon- helps the gardener to foresee ‘threatening’ pests and diseases and making the right decisions towards preventive measurements.

Most common pests/diseases in aloes are aphids, scale insects and cancer.  

For scale insects the best results are obtained by physically removing scale using a cloth.

Occasional aphids on flower clusters and scale insects on leaves. These are relatively easy to control with water (high pressure) of, even better, preventive with a tea of garlic. Aphids are ‘farmed’ by ants. The ants regard aphids as their ‘milk cows’. Keeping ants away, two rings (10 cm or 4 inches space between them) of chalk powder on soil around aloes, minimalise the number of ants and aphids. 

Cancer: Caused by aloe-cancer mite.  This mite lives inside the plant and is the carrier of the virus and cause the cells to multiply and form ugly weird growths.  Cut out the affected part of the plant and let it dry.  General info about pest control and pest and disease prevention can be read elsewhere in this blog  

Propagating

Propagating is best done via cuttings. Sowing is also possible but bear in mind that Aloes hybridize easily. 

Southern Africa is home to a few hundred Aloe species. Two of our favorites are the Aloe perfoliata and the Aloe polyphylla. 

Aloe perfoliata

Growing A. perfoliata is very easy. The best results are achieved by simply making stem cuttings. Allow cuttings to dry for a few days and insert into river sand and keep moist. The roots appear after about two weeks. Seeds must be sown as fresh as possible. When kept too long they are parasitized by small crawling insects. The best time for sowing would be in the winter, June to July. Use coarse river sand and cover seeds lightly, then keep moist. It is advisable to treat seeds with a tea of khaki-bush, as seedlings are prone to damping off, a fungus that eventually kills the young plants. Simply add tea to the soil. After germination, when plants are about 20 to 30 mm, plant over using a sandy-loam medium. If you have a garden with clay soil, use some bone meal to break up and nourish the soil. Mature plants in the garden may from time to time be subjected to attack from scale insects and aphids.

Aloe polyphylla originates from high, relatively cold, altitudes in Lesotho. It is a very difficult plant to cultivate in the open in the Western Cape. It’s main requirement is well-drained soil. It performs best when planted on a slope (or planted up at a slight angle so water does not collect in the spiral), where it can enjoy sun, or part (afternoon-) shade in the hottest areas. It also does well in pots. Water requirements depend on soil and weather. They are generally suited to low water, but prosper with some summer water. 

Information about South African Aloe species can be obtained via one of the websites of the National Biodiversity Institute. This site contains a wealth of info of many indigenous plants including succulents.