Origin and Common Names
Coleus melanocarpus, also known as Plectranthus melanocarpus, is a flowering plant belonging to the Lamiaceae or mint family. It is native to sub-Saharan Africa, including Angola, the Democratic Republic of Congo, Zambia, and Zimbabwe. The plant is known by several common names, including black fruit coleus, black seed coleus, and black seed plectranthus.
Appearance
Coleus melanocarpus is a perennial herb that typically grows up to 60cm tall. It has a semi-succulent stem that is quadrangular in shape and produces a mild aroma when crushed. The leaves are soft, hairy, and rounded with a scalloped edge, measuring 1-3cm in length. The texture and colour of the leaves vary from light green to dark green with a purplish-red underside. The plant produces small, tubular, whitish to pinkish flowers from the leaf axils, which attract pollinators.
Uses
Coleus melanocarpus has been traditionally used for medicinal purposes in African countries. The roots and leaves are used to treat skin infections, fever, malaria, and dysentery. It is also used as a remedy for snakebites and scorpion stings. The plant's extracts have anti-inflammatory, antioxidant, antibacterial, and antifungal properties.
Coleus melanocarpus is also used as an ornamental plant for its attractive foliage, which can be used in indoor plant arrangements or in outdoor gardens. It grows well in a warm and humid climate with well-draining soil, and partial to full shade. Propagation can be done through stem cuttings or seeds.
Light requirements
Coleus melanocarpus thrives in bright but indirect light. The plant prefers to be shielded from direct sunlight to avoid leaf damage and scorching. As a houseplant, Coleus melanocarpus can grow in fluorescent or incandescent lighting but requires at least 12-14 hours of light per day.
Temperature requirements
The ideal temperature range for Coleus melanocarpus is between 18°C and 26°C. The plant cannot tolerate extreme temperature fluctuations, and exposure to below 16°C can damage the leaves, thus affecting the plant's growth. On the other hand, exposure to temperatures above 30°C will cause the plant to wilt and affect its overall health.
Soil requirements
Coleus melanocarpus requires well-drained soil that retains moisture and nutrients. A mixture of peat moss and perlite with a pH of 6.0-7.5 yields the best results. The soil should be kept moist but not waterlogged, as exposure to waterlogging can rot the roots, leading to plant death. Adding organic matter such as compost can improve the soil's fertility and provide essential nutrients for the plant's growth.
Cultivation of Coleus melanocarpus
Coleus melanocarpus is a tropical plant that requires warm and humid conditions to grow well. To cultivate this plant, you need to provide the right soil, light, and temperature conditions.
One of the most important factors when it comes to the cultivation of Coleus melanocarpus is soil. The plant prefers well-drained soil that is rich in organic matter. The pH of the soil should be slightly acidic, ideally between 5.5 and 6.5.
The plant also requires bright, indirect light to grow well. It needs about 6 to 8 hours of sunlight per day, but too much direct sunlight can cause the leaves to burn. To avoid this, you can place the plant near a window with a sheer curtain or provide shading in the form of a sheer cloth or other material.
Watering Needs
Coleus melanocarpus requires consistent watering to thrive. The soil should be kept moist, but not waterlogged. Water the plant when the top inch of soil feels dry to the touch. Avoid overwatering, as this can lead to root rot and other fungal diseases.
A good way to ensure that the plant is getting enough water is to check for signs of drought stress, such as wilted leaves or a drooping stem. If you notice these signs, it's time to water the plant.
Fertilization
Like most plants, Coleus melanocarpus requires regular fertilization to promote healthy growth and development. You can use a well-balanced liquid fertilizer every 4 to 6 weeks during the growing season. Avoid fertilizing during the winter months, as the plant is dormant at this time.
When applying fertilizer, be sure to follow the instructions carefully and do not over-fertilize, as this can lead to burning of the roots and foliage.
Pruning
Pruning is an important aspect of caring for Coleus melanocarpus. It helps to promote bushy growth and prevent the plant from becoming too leggy. You can prune the plant by pinching off the tips of the stems, which will encourage side shoots to grow.
Pruning can also be used to remove any dead or diseased foliage, which can help to prevent the spread of disease and ensure that the plant stays healthy and thriving.
Propagation of Coleus melanocarpus (Gürke) Robyns & Lebrun
Coleus melanocarpus (Gürke) Robyns & Lebrun is a perennial herb that belongs to the family Lamiaceae. This plant is commonly known as Black-fruited Coleus and is native to tropical regions of Africa. It is an attractive plant that grows up to 1 m high and has beautiful green foliage with purple flowers. Propagation of Coleus melanocarpus can be done through various methods.
Propagation by Stem Cutting
Stem cutting is the most common and preferred method of propagation of Coleus melanocarpus. It involves the following steps:
- Select a healthy stem from the mother plant that has at least two nodes.
- Cut the stem just below the bottom node using a sharp and sterile knife.
- Remove the leaves from the bottom node of the stem.
- Dip the bottom end of the stem in rooting hormone powder to stimulate root growth.
- Plant the stem in a pot or tray filled with a well-draining potting mix.
- Water the cutting thoroughly and cover it with a plastic bag to maintain humidity and prevent moisture loss.
- Put the pot or tray in a bright and warm place, away from direct sunlight.
- After a few weeks, the cutting will start growing roots and new leaves.
- Once the roots have formed, transplant the new plant into a larger pot or in the garden.
Propagation by Seed
Propagation by seed is also possible, but it is not the preferred method because Coleus melanocarpus rarely produces viable seeds. In case you have seeds, follow these steps:
- Prepare the soil by mixing equal parts of peat moss and sand, or use a seed starting mix.
- Plant the seeds on the surface of the soil and press them gently into the soil.
- Spray the soil lightly with water to moisten it.
- Put the pot or tray in a warm and bright place, away from direct sunlight.
- Keep the soil moist by spraying it lightly with water, but avoid overwatering as it may cause the seeds to rot.
- After a few weeks, the seeds will germinate and start growing.
- Once the seedlings are big enough, transplant them into individual pots or in the garden.
Disease Management
Coleus melanocarpus is susceptible to various fungal and bacterial diseases like leaf spot, powdery mildew, and stem rot, which can stunt its growth and lead to reduced yield. Preventive measures like planting disease-resistant cultivars, maintaining proper distance among the plants to promote air circulation, removing infected leaves, and avoiding excessive watering can help reduce the incidence of diseases in the crop.
To treat fungal and bacterial infections, apply fungicides or bactericides like copper oxychloride, streptomycin, or kasugamycin to the plant's foliage or soil. However, it is necessary to read the product labels and use them as per the recommended dosage and frequency.
Pest Management
Coleus melanocarpus can attract various pests like mealybugs, aphids, spider mites, and whiteflies, which can suck the plant sap, distort the leaves, stunt the growth, and increase the risk of fungal infections. Regular monitoring of the plant's foliage for any sign of pest infestation is crucial to control their spread.
Spraying insecticidal sprays like neem oil, spinetoram, pyrethrin, or imidacloprid can help repel or kill the insect pests. Application of sticky traps can help trap adult insects like whiteflies and thrips. Additionally, maintaining proper hygiene by removing plant debris, rotating the crops, and avoiding overcrowding can help minimize pest incidence in the crop.
