(This week, Succulentophile gives way to this article by Peter Bangayan)
The genus Monadenium belongs to the family Euphorbiaceae and comprises of 50 or so species, a majority of which occur in tropical Africa.
Similar to the Euphorbias, they exude a milky sap that can be quite poisonous in certain species. Coming from tropical Africa, many of them are particularly easy to grow here in our tropical climate. Succulent Monadeniums can more or less be classified into three distinct types of growth forms. Some plants are characterized by succulent stems — with small, semi-succulent leaves at the tips near the growing points. Examples of these types of plants are Monadenium lugardae, M. ellenbeckii and M. guentheri. There are also forms with thick bushy stems covered with semi-succulent leaves. Plants with this type of growth include Monadenium torrei, M. elegans and M. spinescens. A small number of Monadeniums such as Monadenium stoloniferum, M. coccineum and M. rubellum have small tuberous roots with thin semi-succulent stems and leaves. A number of plants have a combination of two forms such as succulent stems and tuberous roots. Examples of these are Monadenium magnificum and M. arborescens. In common with most succulent Euphorbias, Monadenium flowers are small and insignificant but can be quite colorful in some species.
Monadeniums like most succulents need bright sunlight to grow well. If the plants are grown in shade, the stems and leaves become soft and straggly. Plants grown in shade also become very susceptible to pest and diseases.
Monadeniums should do well with any standard cactus mix. Most Monadenium plants can tolerate a bit of over watering but as a rule of thumb, water the plants only when the medium is almost dry.
A few species of Monadenium have rest periods, which can be a different season for each species. Some will go dormant when the weather becomes cold, while some rest during the hot summer months. A good indication that the plant is dormant is when all the leaves fall off the plant. During the dormant season, do not overwater the plant as this can cause the plants to rot.
Monadeniums respond well to feeding during the active growing seasons. Slow-release, granulated, organic or liquid fertilizers with low nitrogen content are recommended. Feed the plants half or a fourth of the recommended dosage for houseplants.
The usual pests, which can attack Monadenium plants, are scales and mealy bugs. These insects can be controlled using a proprietary contact insecticide such as Malathion or with systemic insecticides. Extra care must be taken when applying these poisonous chemicals. Organic or natural insecticides can also be used and they are much safer for the hobbyist and the environment. Examples of natural insecticides are the oil and detergent sprays, which suffocate the insects by coating them with oil, while the detergent component of the spray dissolves the protective waxy coating of scales.
The most common diseases, which afflict Monadeniums as well as most succulent plants, are bacterial rot and fungal rot. Overwatering and growing in poor environment (no sunlight or air circulation) are the usual causes that can lead to bacterial or fungal rot. Bacteria and fungi usually enter through the roots or a wound in the stem, the wound may be caused by mechanical injury or insect bites too small to be seen.
When a plant is infected by bacterial or fungal rot, remove all rotting and affected portions immediately with a clean and sharp knife. Dry off the plant for a week in a brightly lit and airy place then replant when the cut portion forms a callus. If the plant continues to rot, it means that the bacteria or fungi have gone too far into the plant for it to be saved.
Propagating Monadeniums is easy. They can usually be propagated by seeds or by cutting. To get seeds from plants, cross-pollinate two flowering plants by transferring the pollen from one plant to the stigma of the other plant. If fertilization is successful, the ovary of the flower should start to swell and in a few weeks dry up and release seeds. Plant the seeds as soon as possible as the seeds of Monadenium have a very short shelf life. Many succulent Monadenium and Euphorbias are not self-fertile so you need two plants — which are not clones — to be able to produce seeds by cross pollination. When the seeds germinate, put the plants in a bright (but not direct sun) place. The seedlings should grow into their adult forms in a few months time.
Monadenium plants for beginners include Monadenium guentheri, M. stapelioides, M. heteropodum, M. ellenbeckii and M. gilletii. These plants have long, snake-like succulent stems topped with small leaves. They are best grown in tall narrow pots or hanging pots as they tend to sprawl. Monadenium lurgardae, M. ritchiei, M. renneyi and the very rare M. stellatum have more upright stems topped with small leaves. Plants with upright but thicker stems are the rarer Monadenium schubei and M. reflexum. These two plants are harder to grow and are prone to rot when overwatered during their dormant period. Monadeniums with tuberous roots and thin untidy stems and semi-succulent leaves include the common M. coccineum, the rare M. canellii, M. investum and M. crispum.
Other Monadenium plants that have very thin stems growing out of small tubers are M. stoloniferum, M. rhizophorum and the rare M. majus.
Monadenium forms, which grow to several feet tall, are M. arborescens, M. magnificum and M. spectabile. Monadenium plants with succulent bonsai potential include M. spinescens, M. elegans and M. torrei, which form thorny branching stems with peeling bark that eventually become a small bush.
All in all, most Monadeniums are easy to grow and are highly recommended for beginners. Plants such as M. guentheri, when well grown, can make for a beautiful clump of snake-like stems, which can be a beauty to behold and appreciate.