Adeniums are succulent flowering plants native to Arabia and Africa. They have adapted well to the weather conditions of South-East Asian tropical countries like India.
Also known as Desert Rose, these plants can become an obsession with plant lovers, their attraction being the unusual caudex (the lower swollen part of the stem) having fascinating shapes. They can be nurtured as bonsai, planted in a landscape or grown as container plants.
The plant wakes up after winter hibernation in the spring, it enthralls us with its bunches of pretty flowers in the heat of the summer and through autumn, before gradually slipping into a lull as the winters arrive.
Soil and Containers:
As the name implies, the desert rose plant is acclimated to dry, desert-like conditions. Its thick swollen caudex stores water for its needs, thus soil texture should be light and airy so as to drain off excess water quickly. In fact, the composition of the soil is the most vital aspect in the care of this plant.
The following soil composition is considered healthy and nutritious for the plant: 50% washed, and sieved coarse part of badarpur or cinder.
40% matured leaf compost, cow dung manure or kitchen compost. 5% bone meal.
5% neem khal.
Small amounts of coarse charcoal and fungicide powder ( cinnamon) are added to the above composition and mixed thoroughly. It is left for two weeks to mature before being used. The soil pH should hover around the neutral value.
Low, wide shaped planters are used to expose the attractive shape of the caudex. Terracotta pots provide best aeration but one can also use ceramic and plastic ones with several drainage holes. Shallow terracotta or ceramic trays make a nice presentation for these naturally bonsai shaped plants, besides encouraging the roots to spread and provide a more stable base.
Oversized containers should be avoided.
Water:
In spring and summer, adeniums need deep, yet infrequent watering. The top layer of the soil should dry up to an inch or more before being watered again. The roots should never stand in wet medium, moisten the medium just enough for roots to soak up the water quickly. During the rainy season, pots can be tilted to avoid accumulation of water and thus prevent root rot. The rot can spread to the caudex and stem and many a times it becomes difficult to save the plant. If the plant is part of a landscape, it is prudent to position it on an incline so that the water can drain off quickly, especially during the rains.
Towards the end of October, as the plant starts showing signs of dormancy, with leaves turning yellow and falling off, watering frequency needs to be reduced drastically. Light misting on the caudex and soil can be done if the caudex shrinks or feels soft due to loss of moisture. Cold winter winds and dew collecting on the plant can cause severe damage, leading to stem rot which can eventually kill the plant. Needless to say that winter rains can play havoc on the adenium, as the soil may not dry for days together.
Sunshine:
Desert roses bloom well in bright, full day sunlight. If kept in the shade, these plants will not bloom and become leggy with weak stems. Early spring until mid-summer is the ideal blooming time for adeniums, as bright sun stimulates flowering. At the beginning of June blooming ceases for 6-8 weeks and the plant should be protected from the scorching afternoon heat.
The second period of blooming begins in the early autumn months, before the plant moves into its dormancy period.
Feeding:
During the active growth and flowering period, diluted liquid fertilizer or Jeevamrutha can be given every 15 days to boost its growth. In the rainy season and winters, feeding should be avoided.
Pruning and Repotting:
The adenium plant can be given a desirable shape and its height maintained by pruning during September and February. Careful pruning and maintenance is required to develop it as a bonsai. After pruning, the sap oozing from the wound should be wiped, and the exposed part immediately covered with a good quality fungicide powder such as cinnamon to prevent any infection. (The sap of some these species is considered poisonous and used as arrow poison in African countries) This activity should be avoided completely in the rainy season as high humidity makes the plant susceptible to fungal infection. Likewise, adenium should be left undisturbed in the dormant period of winters. Pinching and light pruning should be done during the active period as and when required to keep it well groomed and get more branches for flowering. The pruned branches can be used as cuttings for propagation.
Mid-January is an appropriate time to repot the plant and prepare it for flowering. Extra roots can be trimmed off and the caudex raised by a few inches to expose its interesting features. The plant should be watered 2-3 days after repotting.
Diseases:
The adenium plant is usually not attacked by pests but fungal infection can easily kill the plant. Giving just the right amount of water and adequate sunlight are the key to keeping the plant healthy for several years. Fungal infection can be noticed when roots, caudex or stems show signs of rot (that part becomes dark, soft and pulpy), or when sudden yellowing of leaves or leaf drop occurs. The infected portion should be removed immediately with a sterilized tool so that the healthy part is exposed. Following this, the sap of the exposed part of the plant is cleaned, covered carefully with antifungal powder and left to dry out for a couple of days before repotting again in fresh soil.
As a precaution, 5 gm fungicide powder mixed in 1 L of water should be sprayed on the plant as well as given around the roots every month. The frequency can be increased during the rainy season.
Another organic preventive measure is to spray neem oil and/ or a soapnut solution. The soapnut solution spray is followed by a spray of a vinegar solution the next day. This spray is made by mixing 5 ml of vinegar or 5ml of lemon juice in 1 litre of water. The latter combination of sprays keeps leaves healthy and shiny.
Propagation and Grafting:
Propagation can be done by seeds obtained from bean shaped seed pods or by cuttings. The cutting- grown plants however do not develop a thick, swollen caudex like the seed grown plant.
Seed-grown plants are genetically not identical to the mother plant due to cross- pollination. The seed pods appear in pairs and become swollen as they ripen. To prevent the seed pod from bursting and its seeds being dispersed by the wind it should be tied with either a rubber band or a thread. Mature seeds are collected, the dandelion-like fluff removed from the ends and planted within a few days of collection.
Desirable species are commonly propagated by grafting. Several different cuttings can be grafted on a plant to give it an aesthetic appeal.
Following the rules and precautions for maintenance of adeniums can be rewarding, as these plants can live with us for a life-time and enthrall us with their beautiful foliage, flowers and shapes.