Overview
Grewia melindensis J.R.Drumm. is a shrub or small tree species that belongs to the family Malvaceae. This plant is native to the eastern and southern regions of Africa, and it is commonly called the "Red raisin" due to the dark red fruit it produces.
General Appearance
Grewia melindensis is a deciduous perennial shrub or a small tree, which grows up to a height of 2-8 m and a width of 2-5 m. The bark is thin, smooth, and greyish-brown in color. The leaves are simple, alternate, and ovate-shaped, with serrated margins. It produces small but fragrant flowers, which are pale pink, white, or cream in color and grow in clusters near the tips of the branches. The fruit is small, round, and dark red in color, measuring about 1 cm in diameter, with a crispy texture and sweet taste.
Common Names
This plant is commonly known as the "Red raisin" in English, "Udakwa" in Swahili, "Mululuza" in Luganda, "Infunywa" in Zulu, and "Tsamutlwa" in Sesotho.
Uses
The fruit of Grewia melindensis is edible and is often consumed raw or used in the preparation of juice, jellies, ice cream, and other desserts. The leaves and bark of this plant are used in traditional medicine to treat various ailments, such as stomach ache, diarrhea, dysentery, and fever. The wood of this plant is also used in the production of small utensils, tool handles, and musical instruments.
Light Requirements
Grewia melindensis is known to grow well in direct sunlight and partial shade. In its natural habitat, it is commonly found growing in open forests and in the understorey of larger trees. Therefore, it can tolerate varying degrees of light. Young Grewia melindensis plants require more shade than older plants.
Temperature Requirements
This plant is native to warm tropical regions and hence can be grown in areas with temperatures ranging between 20°C and 35°C. Grewia melindensis can tolerate heat and low humidity levels, making it ideal for cultivation in arid and semi-arid regions. During the cooler months, the plant may need additional protection from frost.
Soil Requirements
Grewia melindensis grows best in well-drained soils with a pH range of 6.0 to 7.5. It prefers soils that are rich in organic matter and can retain moisture, though it is adaptable and can also grow well in soils of low fertility. The plant is capable of growing in a variety of soils, including sandy, loamy, and clay soils. However, good drainage is essential to prevent waterlogging and root rot.
Cultivation
Grewia melindensis J.R.Drumm. can be cultivated by using seedlings or stem cuttings. It can grow in a wide range of soils, but it prefers sandy soils and loamy soils. It requires full sunlight or partial shade for optimal growth. The plants should be spaced about 5-6 meters apart from each other to allow sufficient space for growth.
Watering Needs
Grewia melindensis J.R.Drumm. requires moderate watering during its establishment period. After establishing, it becomes drought-tolerant and can survive on rainwater. However, it will require supplementary watering during prolonged dry periods, particularly when it is producing fruits.
Fertilization
When cultivated in poor soils, applying organic fertilizers during planting can help improve the quality of the soil. After the first year, apply nitrogen-rich fertilizers to promote vegetative and fruit growth. Apply potassium and phosphorus-rich fertilizers during the second and third years of growth to enhance fruit quality and quantity.
Pruning
Grewia melindensis J.R.Drumm. requires minimal pruning. Prune out dead, damaged, or infected parts of the plant. Prune the plant to maintain an open canopy that enhances light penetration and improves air circulation. It is prudent to prune the plant after harvesting fruits to promote rapid regrowth and maintain a manageable growth form.
Propagation of Grewia melindensis J.R.Drumm.
Grewia melindensis J.R.Drumm. can be propagated through seeds, cuttings, and grafting.
Seed Propagation
The seeds of Grewia melindensis J.R.Drumm. should be collected from fully matured fruits. The collected seeds should be cleaned and soaked in warm water for a period of 24 hours. After soaking, the seeds are sown in a well-prepared nursery bed, in rows spaced about 30-40 cm apart. The seeds should be covered with a thin layer of soil, and the bed should be watered regularly. Germination usually occurs within 2-4 weeks. The seedlings can be transplanted into individual containers or directly into the field after 4-6 months of growth.
Cutting Propagation
Softwood cuttings, semi-hardwood cuttings, and hardwood cuttings can all be used to propagate Grewia melindensis J.R.Drumm. Softwood cuttings should be taken from new growth, semi-hardwood cuttings should be taken from current season’s growth that has matured slightly, and hardwood cuttings should be taken from the previous season’s wood. The cuttings should be about 10-15 cm in length and should have at least 2-3 nodes. The cuttings should be treated with rooting hormone and planted in well-prepared soil in a nursery bed or in individual containers. The soil should be kept moist, and the cuttings should be protected from direct sunlight. Rooting usually occurs within 4-6 weeks, and the cuttings can be transplanted into the field after 6-8 months of growth.
Grafting Propagation
Grafting can also be used to propagate Grewia melindensis J.R.Drumm. In this method, a scion of the desired variety is grafted onto a rootstock of a related Grewia species. The scion should be taken from a healthy plant with desirable characteristics. The rootstock should be chosen for its compatibility with the scion and its ability to provide a strong root system. The graft should be made in late winter or early spring. The graft union should be protected from direct sunlight and excessive heat until it has sufficiently healed. The grafted plant should be transplanted into the field once it has established a strong root system.
Disease and Pest Management for Grewia melindensis J.R.Drumm.
Grewia melindensis J.R.Drumm. is a small to medium-sized tree that is commonly found in sub-Saharan Africa. While the tree is relatively hardy, it can be affected by a range of diseases and pests.
Common Diseases
The most common diseases that affect Grewia melindensis J.R.Drumm. are:
- Leaf Rust: Leaf rust can affect the leaves of the plant, causing them to turn brown and fall off. It is caused by a fungus and is most common in areas with high humidity. To manage this disease, it is important to remove and destroy infected leaves and spray the tree with a fungicide.
- Canker: Canker can affect the bark of the tree, causing it to crack and split. This can lead to secondary infections and, in severe cases, the death of the tree. To manage canker, it is important to prune away infected branches and avoid overwatering the tree.
- Root Rot: Root rot is caused by a fungus and can affect the roots of the tree. Symptoms of root rot include yellowing of leaves, wilting, and stunted growth. To manage this disease, it is important to avoid overwatering the tree and to ensure that the soil is well-draining.
Common Pests
The most common pests that affect Grewia melindensis J.R.Drumm. are:
- Mealybugs: Mealybugs are small, white insects that suck the sap from the plant. They can cause the leaves to turn yellow and fall off. To manage mealybugs, it is important to remove them by hand or spray the tree with an insecticide.
- Caterpillars: Caterpillars can eat the leaves of the tree, causing damage to the plant. To manage caterpillars, it is important to remove them by hand or spray the tree with an insecticide.
- Thrips: Thrips are small, winged insects that feed on the leaves of the tree. They can cause the leaves to become discolored and distorted. To manage thrips, it is important to remove them by hand or spray the tree with an insecticide.
Overall, to maintain the health of Grewia melindensis J.R.Drumm. it is important to practice good cultural practices, such as regular pruning and providing the tree with the appropriate amount of water and fertilizer. Additionally, monitoring the tree for signs of disease or pests and taking appropriate action can prevent infestations from becoming too severe.
