Basic Information
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius is a small deciduous tree belonging to the family Fabaceae. It is also commonly known as round-leaf vernonia.
Origin and Distribution
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius is native to southern Africa, including Zambia, Zimbabwe, Botswana, Namibia, and South Africa. It is commonly found in dry woodland, savanna, and scrubland environments.
Appearance
The tree can grow up to 7 meters tall, with a distinctive rounded crown and a short trunk. The leaves are shiny, round, and green above while they have hairs on their lower surfaces. The flowers are small and yellow, growing in clusters at the end of the branches. The fruit is a flat pod up to 8 cm long containing several seeds. The roots are deep, making it drought-resistant but difficult to transplant.
Uses
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius has significant uses in traditional medicine. The bark of the tree is used to make a tea that is used to treat various ailments such as malaria, stomach complaints, and headaches. The leaves of the tree crushed and soaked in water are used to treat wounds. The wood of the plant is hard and heavy, and it is used for furniture and carving. The tree is also used in reforestation and erosion control programs, as it is an important plant due to its deep root system that conserves soil and water.
Light Requirements
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius grows best in areas with full sun exposure for most of the day. This plant can adapt to moderate levels of shading but will not thrive in areas with dense tree cover or insufficient light. Therefore, it is ideal for outdoor planting in open fields, savannahs, and woodlands.
Temperature Requirements
The optimal temperature range for Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius growth is between 20°C and 30°C. This plant is well adapted to the hot and dry tropical conditions of sub-Saharan Africa. It can withstand short periods of drought, but prolonged dry spells can lead to stunted growth and increased susceptibility to pests and diseases.
Soil Requirements
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius prefers well-drained and fertile soils with a pH range of 5.5–7.5. This plant is best suited for loamy or sandy soils with good drainage and aeration. It can also grow in rocky soils, but not in poorly drained clay soils. Additionally, the plant requires adequate levels of nutrients, including nitrogen, phosphorus, and potassium, for optimal growth.
Cultivation
Pterocarpus rotundifolius requires full sunlight exposure for optimal growth. The plant is drought-tolerant and can survive in poor soils, but it prefers well-draining soils. The best time to plant this plant is during the rainy season.
Watering Needs
Newly planted Pterocarpus rotundifolius should be watered regularly until they are established. The plant requires moderate watering during the first growing season. During the dry season, the plant should be watered deeply at least once a week. Too little water causes leaf shedding, while too much water causes root rot.
Fertilization
Pterocarpus rotundifolius benefits from regular fertilization with organic, slow-release fertilizers. The plant should be fertilized from the beginning of the growing season and can be fertilized again after the first flush of growth. Fertilization should be minimized during the dry season.
Pruning
Pterocarpus rotundifolius pruning should be done during the dry season when the plant is dormant. Dead, diseased, and damaged branches should be removed. The plant can be trained early to achieve a desired shape or size. Pinching back the growing tips of young plants can encourage branching and make the plant bushy. The plant should be pruned minimally to avoid damage to the tree and to maintain its attractive shape.
Propagation
Pterocarpus rotundifolius (Sond.) Druce subsp. rotundifolius can be propagated through seeds and vegetative means.
Seed Propagation
The seeds of P. rotundifolius are enclosed in hard, woody pods. These pods should be collected when they are fully matured and have started to split open. The seeds should then be extracted from the pods and soaked overnight in water, using a container that allows air to circulate. This process should help soften the seed coat and promote germination.
The seeds should be sown in well-drained soil mixed with sand or vermiculite in a nursery bed or polybag. The depth of sowing should be about 2-3 cm. Watering regularly during the first few weeks is recommended.
Germination should occur within 3-4 weeks, and seedlings can be transplanted to individual pots after four months. After one year, the seedlings can be planted outside.
Vegetative Propagation
P. rotundifolius can be propagated vegetatively through cuttings, layering, and marcotting.
Cuttings: The cuttings should be taken from mature branches, 4-6 cm long, and should be planted in a well-drained soil mix of sand and compost. The cuttings should be watered regularly until they root, which should take around 8-10 weeks. Once rooted, they can be transplanted to individual pots before planting outside.
Layering: Layering is a good method of propagation if you want to retain the genetic characteristics of the parent plant. To propagate via layering, identify a low growing stem and dig a small trench beside it. The stem should then be bent into the trench and secured in place with a wire. Cover the stem with soil and water it regularly until it roots. After it has rooted, the new plant can be separated from the parent plant and transplanted elsewhere.
Marcotting: Marcotting is similar to layering, but it involves wounding the stem to promote root growth. A branch should be selected, and a 2-3 cm wide section of bark removed from the stem. The wound should then be covered with moist sphagnum moss or similar material. After 4-6 weeks, roots should start to form around the wounded area. The new plant can then be separated from the parent plant and transplanted elsewhere.
Disease Management
Pterocarpus rotundifolius is not prone to many diseases, but should still be monitored for potential fungal and bacterial infections.
Signs of disease include wilting, yellowing, and spotting of leaves, as well as lesions or cankers on stems and branches. If any of these symptoms are detected, it’s crucial to take action promptly to prevent the further spread of the disease.
Preventative measures include ensuring adequate plant spacing for adequate airflow and avoiding overhead watering that can increase humidity levels and trigger infections. Regular pruning to remove diseased branches is also beneficial.
If a disease is detected, it can be controlled with fungicides or bactericides, depending on the specific pathogen causing the issue. It’s essential to consult with a professional to ensure the proper course of action.
Pest Management
Pterocarpus rotundifolius is susceptible to several pests, including termites, carpenter worms, and webworms.
Termites can cause significant damage to the root system, leading to poor growth and wilting of the plant, while carpenter worms damage the stem and branches, causing defoliation and sometimes complete death of the plant. Webworms primarily affect leafy tissue, causing leaves to curl and turn brown.
Control measures include regular monitoring to detect possible infestations early on, avoiding planting in areas prone to pests, and practicing good soil and plant hygiene. Insecticides can also be used as a last resort to treat infestations but should only be applied by professionals.
