Succulents as ‘bonsai’ subjects

(This week, the author gives way to an article by Peter Bangayan.)

The Japanese term "bonsai" literally means "container" or "tray gardening." It is used to denote the miniaturization of trees and plants by way of confinement and pruning of the roots and shoots. Bonsai gardening uses many tools such as wires for training the plant and special cutters to prune roots and shoots. Bonsai gardening is an art form and there are many different styles of bonsai.

Here, the term bonsai is used in a very loose manner to denote succulent plants that can be trained to look like miniature replicas of old trees and shrubs in their natural environment.

In the succulent world, there is a class of plants loosely based on growth forms called caudiciform and pachycaul succulents. These plants are very good candidates for creating "bonsai" succulents. Caudiciforms are succulents that have a large underground tuber or roots called caudex. In the wild, the tuber helps the plant survive the dry desert environment by acting as its storage for food and water. Pachycauls, on the other hand, are plants that have large, swollen trunks and some can almost look cactus-like.

Growing most caudiciforms and pachycauls is easy. A good growing medium must have good drainage and must contain enough food for the plant. A mixture of 1/3 sharp sand, 1/3 rich compost, and 1/3 garden loam is recommended. For a richer medium, a larger proportion of compost than garden loam is used in the mix. For a poorer medium, a larger proportion of garden loam than compost is used.

Many fast-growing plants, such as Adenium obesum, Pachypodium lamerei, Pachypodium geayi, Pachypodium saundersii, Pyrenacantha malvifolia, etc., require a rich potting-soil medium while the slower-growing ones such as Pachypodium brevicaule, Pachypodium namaquanum, Dorstenia ellenbeckii, etc., need a poorer growing medium.

Good sunlight is a must to grow beautiful, compact plants, but different plants have different tolerances for sunlight. Many desert plants can tolerate full sun, while other plants that grow under the protection of larger plants or grow underground in the wild need bright but not direct sunlight. Plants grown in the shade usually become weak and etiolated and will not look their best.

Water and feed your plants when they are in active growth. Depending on the season and the place where they originated, plants will usually put out new leaves when they are at the start of the active growing season. Water plants thoroughly but let the soil mix almost dry out before the next watering. Feed plants with a fertilizer low in nitrogen, high in potassium and phosphorous, and also use a fertilizer with trace elements.

Fast-growing plants like Adenium obesum, Pachypodium lamerei and Pachypodium geayi are very water- and fertilizer-hungry during their active growing period and must be watered and fed (follow dilution for roses) regularly. Slower-growing plants should be given less fertilizer. Feeding the plants once every two weeks is quite adequate. Some people use slow-release fertilizer, which can last about two to three months per feeding. Use slow-release fertilizer only at the start of the active growing period and stop about a month or two before the resting period of the plants.

During the resting period, succulent caudiciform and pachycaul plants either stop growing new leaves and branches or shed their leaves. During this period, water plants sparingly and never feed them to avoid bacterial and fungal rot. Different plants have different resting periods — some plants rest during the summer while others during the winter months. By observation and doing a little research, it is easy to ascertain when a particular plant is resting or in active growth.

Succulent plants hardly ever get pests when they are grown well — that is, when they are given enough light, water, feeding, and grown in the right medium. However, there are times — especially when a plant is dormant or resting — when it can be vulnerable to scale insects and root mealybugs. Any proprietary insecticide should be able to control these pests. Following the instructions in administering insecticides is very important because they are very poisonous chemicals.

One of the new trends in controlling pests is by the use of natural, organic or nontoxic insecticides. There are several formulas available on the Internet; most of them use a detergent as a wetting agent and vegetable oil with some irritant, such as crushed chili, to suffocate and kill the insects.

Fungal and bacterial rot is one of the most common problems with cacti and succulent growers. Growing your plants in a well-aerated and sunlit area can usually prevent rot. Also never waterlog your plants, as this will most certainly lead to rot, especially when the plant is dormant. To avoid rotting, many collectors raise the enlarged roots of the plant with only the root tips growing into the soil to collect water and nutrients. This will also show off the bonsai character of the plant to advantage. This, however, is done only when the plant has matured enough to have grown a large underground root system. If a small or juvenile plant’s root is raised very early, the plant will not show enlarged, "old"-looking roots and this will slow down its growth.

Some succulent plant families that are good bonsai subjects are:

•Adenia, from the passionflower family, originates from Africa, and many species of this family have either a caudex or pachycaul form of growth. Some recommended plants are Adenia glauca, A. globosa, A. spinosa, A. venenata, and the very rare A. pechuelii.

•Adenium, or what we call "Bangkok calachuchi" when grown from seed, makes a beautiful pachycaul plant with beautiful, star-shaped flowers in red, pink, white or combinations of these colors. Species such as Adenium arabicum, A. obesum, A. oleifolium, A. somalense, A. multiflorum make good bonsai subjects as well as the numerous hybrids available on the market.

•Dorstenia of the family Moraceae are miniature succulent plants with very unusual star-shaped flowers; a number of them, such as Dorstenia barnimiana and D. ellenbeckii, are geophytes and have small underground tubers, while some such as Dorstenia foetida, D. crispa, the rare D. gypsophila, and D. gigas have pachycaul-form growth.

•The genus Euphorbia of the large family Euphorbiaceae, which includes a number of commonly seen plants such as the poinsettia, has many succulent members. Many Madagascan and African euphorbias such as Euphorbia ambovombensis, E. capsaintmariensis, E. beharensis, E. rossii, and E. sakarahensis, to name a few, are good candidates for bonsai succulents. Another genus, Monadenium, also belonging to the Euphorbiaceae family, also has some species with bonsai potential — Monadenium elegans and M. spinescens are good candidates.

•Pachypodium from South Africa and Madagascar have many species that can be made to look like bonsai specimens: the tuberous-rooted Pachypodium bispinosum and P. succulentum look the part when their large, tuberous roots are raised in cultivation. Smaller branching Pachycauls, such as P. brevicaule, P. densiflorum, P. rosulatum, and P. baronii, also have potential as bonsai subjects.

There are many other succulent plant species that can be made into bonsai subjects — plants like Fockea edulis and F. crispa, Idria columnaris, Uncarina species, etc. It would certainly be very interesting to try and apply the principles of bonsai gardening to growing succulent plants.