Cacti and Succulents

I shall always have a soft spot for these often prickly characters as they were amongst the first plants I ever grew and must have been responsible for an ever growing interest in plants generally. They can take up very little space and can be left virtually to look after themselves for short periods while their owners are away on holiday. I think they are a good choice as starter plants for prospective young gardeners. Although most garden centres and plant shops sell cacti, I would advise searching out a good cactus specialist as the range, quality and prices should be hard to beat. A visit to one of these places is certainly an eye opener as I am sure there are many more different types of cacti and succulents than you ever thought existed.

Cacti

There are a lot of succulent plants mistakenly referred to as cacti. True cacti are only those plants that are in the family Cactaceae. The feature which puts them in this family is a structure called an areole which is a pad from which grow spines, flowers and branches.

Cultivation

It is necessary to divide cacti into two groups according to where they grow naturally.

Jungle Cacti mostly grow as epiphytes which are plants that instead of growing in the ground grow up in the branches of trees or wherever their shallow roots can find a small niche. The temperatures they are used to are more constantly higher than desert cacti which might have to withstand searing heat by day yet very cool night temperatures. This means that jungle cacti will need a slightly higher winter temperature, between 10° and 13°C (50° and 55°F), to do well. Unlike desert cacti they are also in a moist atmosphere all year round and as such should not be allowed to dry out. However, they should not be overwatered as their roots are not accustomed to being surrounded by wet soil; which is also why they, like desert cacti, prefer a well-drained compost. As they would normally have the shade from tree canopies they like to be slightly shaded in the greenhouse or the leaves will go very yellow. Yellow shrivelling leaves are a common complaint of these plants and can be caused by overwatering, bright sunlight or not enough feed. Apply fortnightly liquid feeds during spring and summer.

Not surprisingly considering their habitat most jungle cacti are wayward in their growth and tend to trail or hang which makes them most suitable for hanging baskets. Plants that fall into this category include Schlumbergera more commonly known as the Christmas or Easter Cactus. A lot of people are confused as to why these sometimes do not flower precisely on these two occasions. In fact this group contains many hybrids which flower over a long period from the end of summer round to Easter. When yours flowers depends on which hybrid you have.

Epiphyllum (Orchid Cactus) are awkward in pots with their long sprawling succulent stems which are always unbalanced and tend to fall over. If you can grow them in a hanging basket they are more manageable. Most of the plants now grown are hybrids with flower colours of white, pink, red, yellow and orange or even mixtures of these. These hybrids tend to be hardier than the species. When established and growing well, which means plenty of food and water in summer, it is possible to prune them after flowering in early summer by cutting out most of the stems which have flowered so that new ones can grow which will flower the following year. E. oxypetalum from Middle and South America is sometimes seen in collections. It is a large growing plant which produces the most glorious huge white scented flowers which unfortunately open in the evening and have usually closed by morning; a good plant for insomniacs.

Rhipsalis (Mistletoe Cactus) are so called because following their small pale pink or cream flowers borne during winter are mistletoe-sized berries which are white, pink, green or black. Succulent stems can be flattened or cylindrical. If you can keep them moist they do rather well if grown epiphytically by binding them on to a piece of dead tree with sphagnum moss around their roots and nylon line to keep them in place. Not to be confused is Riupsalidopsis rosea from Brazil which is a shrubby little cactus that resembles Pjupsalis but tends to be more upright and bears a profusion of small pink flowers. I always find this grows better in a shallow pot or pan.

Desert Cacti

I can remember when I imagined my cacti as coming from deserts full of rolling sand dunes like the Sahara. In fact a desert is classified as an area which receives less than 25 cm (10 in) of rainfall a year. Most cacti grow where there is a bit more to the soil than pure sand. The compost they like is obviously well-drained which means a lot of grit. A leading cactus nursery recommends a compost based on three parts of peat (equal amounts of moss and sedge) and one part of grit. If you wish to use a loam-based compost, extra peat and grit will have to be added to a John Innes No. One or Two.

Light is poorer in winter and most of us are forced through economics to keep the greenhouse temperature as low as we can get away with. Cacti can overwinter at a minimum temperature of 7°C (45°F) and will become dormant requiring very little water. They should not be dried out to the extent that they begin to shrivel, however, so they should be watered a few times throughout this dormant phase although the compost can be allowed to become bone dry in between. This way they do not produce any growth when the poor light would tend to make them distorted or lopsided.

During summer it is important to look after cacti well. So many people think that because they can store water in their tissues they can look after themselves. I suppose this is true in as much as they can survive a lot of neglect. However, I would rather encourage my cacti to flourish than survive which means that they should be watered and given food as regularly as any other plant. Feeding should be with a high potash fertiliser. Special cactus food is available but tomato fertiliser is an acceptable alternative. The better cacti are looked after the better they will grow and flower.

Cacti are extremely easy to propagate which should be done during spring and summer. Sections of stem can be cut or pulled off and inserted in sand to root. Cut surfaces should always be allowed to dry right out before going into the sand. Avoid the temptation to Over-water the sand as this causes cuttings to rot. Some cacti produce offsets which can be pulled away from the parent plant and again persuaded to root by placing them in sand. Do not cover them or put them in a propagator as this could also cause rotting. If a favourite cactus becomes overwatered or begins to die for some reason this usually takes the form of rotting from the base upwards. Cut the healthy live part cleanly away from the base and treat this as a cutting. It is even more important in this case to allow the cut surface to dry off. Even large cacti will root in this way.

It is possible to graft one cactus on to another. This should be done for species which grow very slowly and flower poorly on their own roots. Sulcorebutia species fall into this category. What usually happens is that a shoot of Sulcorebutia will be cut off with a sharp knife or razor blade and a stock plant such as Trichocereus (Echinopsis) is selected which is much the same diameter as the other. This stock plant is cut across only about 2.5 cm (1 in) above soil level. An examination of each cut surface will show an inner ring of vascular tissue. It is vital that these two rings should match up and produce a good union between the two plants. Before they are placed together both stock and scion are pared around the edge of the cut surface to facilitate a better bonding together of the two inner rings. It is necessary to hold the two plants together until the graft has taken. Have the stock in a square pot which will make it possible for two elastic bands to be stretched under the pot and over the top of the graft to keep it in place. This operation is best carried out during spring or summer and kept out of direct sun until the graft has taken.

Spring is the best time to repot a desert cactus, (a) Use thick paper or cloth to protect your hands from the spines, while supporting the cactus, (b) Replace the cactus on a layer of fresh compost, either in a new pot or in the old pot which has been cleaned. Only use a larger pot if the roots are much too large for the original one. (c) Hold the plant at the correct position in the pot—bearing in mind that you must leave a gap at the top for watering. Trickle fresh compost in around the sides, making sure the gaps are all well filled, and firm gently. Finish off with a layer of grit on the surface.

Bright red- and yellow-coloured grafts are often seen which are Gymnocalycium species. They are unable to exist on their own as they contain no chlorophyll with which to synthesise their own food. Personally I think that grafting cacti for the sake of it is an unnecessary gimmick. However, it is a useful technique for growing plants that would otherwise struggle. If the stock is cut low it eventually becomes difficult to see that grafting was used.

Some Favourite Desert Cacti

If I had to name a few good desert cacti which were reliable flowerers, the first that springs to mind is Borzicactus aureospina, a quite large grower with attractive golden spines and bright orange flowers produced almost continuously throughout summer. Rebutias are neat small growing cacti which flower as small plants and very early in the year. Mammilaria as a group are good flowerers tending to produce them in rings around the top of the plant. A particularly free flowering species is M. carmenae which is also a new species in cultivation. The flowers even appear during winter and are a delicate creamy pale yellow.

Mammilarias also have very pleasing forms such as M. bombycina from Mexico with its fish hook spines. Cephalocereus senilis is great fun and earns its name of Old Man Cactus by being covered with long silvery-grey ‘hair’ which makes it look like a wise old wizard. Astrophytum are a great favourite with very few spines and strange markings that put one in mind of a sea urchin. They like a teaspoon of ground chalk in their compost (by the pot) more to benefit from the added calcium than a higher ph. They are particularly prone to being overwatered. Echinocactus grusonii from Mexico is the Golden Barrel Cactus which will grow to form cacti the size of footballs at about ten years old. They are now extremely rare in the wild but are fortunately quite common in cultivation.

For strangely shaped cacti choose, Opuntia species which can be moderate in size such as O. microdasys or large like the several species referred to as Prickly Pears. These are particularly nasty for leaving small prickles embedded in the skin of those a little careless when brushing past. Cleistocactus straussii, the Silver Torch, will make an impressively tall cactus quite quickly and its spines, although quite sharp, are not such a nuisance for becoming embedded in skin. There is even a climbing cactus, Pereskia aculeata from tropical America, which is a primitive cactus that has leaves. This climbs over a large area and flowers very well in the autumn bearing creamy-pink flowers with a pleasant characteristic smell which reminded me of wintergreen to such an extent that we gave it the unofficial common name of Rugby Player’s Leg Plant.

Succulents

It is not easy to define a succulent other than by saying that they are adapted to storing moisture in order to tolerate periods of drought. However, bulbs and some tubers which could also qualify under this description are not included. Although all cacti are also succulent the term ‘succulents’ normally refers to plants other than cacti.

Cultivation is very similar to that of cacti particularly as to soils. The only slight difference is that they usually prefer to be a little warmer in winter and often require slightly more water than a cactus would, to prevent shrivelling. Propagation tends to be more versatile. Leaves oiSedum, Crassula and others will root from the base. Others such as Kalanchoe diagremontianum, the Mexican Hat Plant, produce small plantlets which can be detached and grown.

Some Favourite Succulents

The Aloes are not exactly favourites but are very good plants to start with as they are extremely easy to grow. I think I was put off by looking after vast numbers of them at Kew Gardens. They were grown primarily for research in genetics as they apparently have large chromosomes. It used to be most frustrating when carefully nursed plants would have their roots cut away to be put under the microscope by the scientists. Similar to Aloes but I think more attractive are the Gasterias. Both of these are susceptible to attack by mealy bug.

Cotyledon undulata and C. orbiculata both from the Cape are excellent on account of their leaves being coated with a white almost silvery farinose substance which looks like powder. One has to be extremely careful, though, not to touch or damage this exquisite finish to the leaf. These along with Crassula (C. argentea is the much grown Money Plant or Jade Tree) and Kalanchoe tend to grow and flower mostly in winter. Cotyledons virtually become dormant in summer although they must still have some water. There are some super Kalanchoe which make excellent conservatory plants. K. pubescens is a tall-growing plant with large furry leaves and bears upright stalks of hanging pale orange flowers. Kalanchoe manginii makes an excellent hanging basket plant which can be cut back after flowering and will grow to produce the same effect the following year. Propagation is easy consisting of removing and rooting small plantlets that grow on the inflorescences as the flowers fade. Both these are winter flowerers, usually just after Christmas.

Aeonium make rather architectural specimens. A. arboreum ‘Purpureum’ originally from Morocco makes an attractive branching plant. A. tabulaeforme produces a domed rosette of incredible beauty and detail. This comes from the Canary Islands and ends its life by producing a long flower spike with yellow flowers.

Stapelia are great favourites. S. variegata from the Cape is the most commonly grown. The slightly toothed stems are green with a purple mottling. It is the flowers that are attractive, resembling a maroon tapestry. What is not attractive is their odour reminiscent of rotting meat and authentic enough to fool flies into laying their eggs in the flowers. There are other species with larger even more detailed and pungent flowers. Caralluma and Huernia are very similar and all are in the family Asclepiadaceae which also includes Hoya and Stephanotis—though how such sweet-smelling flowers came to be associated with these stinkers comes as some surprise. Cultivation of these is not easy as they need to be reasonably well watered to prevent shrivelling but quickly begin to rot if too much is given. A dry atmosphere during winter will help.

Lithops are small but fascinating and deserve the name Stone Plants as that is just what they resemble. In fact if they are displayed amongst similar sized stones it is often hard to pick out the real plants. They originate from South Africa and consist of just two swollen leaf structures with a small gap between from which flowers and new leaves eventually arise. Most problems with these are caused by overwatering and low light. Between September and spring no water should be given at all, a little between March and June and normal watering between June and September. Seed is easy to come by and easy to grow. They need a very gritty compost to do well.

30. June 2013 by admin
Categories: Tips and Advice | Comments Off on Cacti and Succulents

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