Description:
Indigofera costata Guill. & Perr. subsp. macra (E.Mey.) J.B.Gillett commonly known as the Narrow-leaved River Indigo is a member of the Fabaceae family. It is a much-branched shrub which can grow up to 2 m tall.
Origin:
The plant is native to South Africa, Zimbabwe, Mozambique, Swaziland, and Botswana.
Common Names:
The plant is commonly known as Narrow-leaved River Indigo, Indigofera, River Indigo, and Kaross.
Uses:
The plant is known for its blue dye, obtained from its leaves, stems, and roots. Hair dye can also be obtained from the same sources. The plant is used in traditional medicine for the treatment of various ailments such as tuberculosis, dysentery, and cancer. The plant is also used as a natural insecticide due to its insecticidal properties.
General Appearance:
The plant has long, narrow, and feathery leaves that are about 6 to 10 cm long and 0.5 to 2 mm wide. The plant produces pink or purple flowers that bloom from August to February. The fruit is a cylindrical pod about 2.5 to 5 cm long and 3 to 4 mm wide, containing small, dark brown seeds.
Light Requirements
Indigofera costata subsp. macra requires full sunlight for optimal growth and development. It can tolerate some shading, but prolonged periods of shade can hinder growth and flowering.
Temperature Requirements
Indigofera costata subsp. macra is a warm-season plant that thrives in temperatures between 20°C to 30°C. It is not tolerant of frost and requires protection during cold weather.
Soil Requirements
Indigofera costata subsp. macra prefers well-drained and fertile soils with a pH range of 6.0 to 7.0. The soil should be rich in organic matter and capable of retaining moisture.
The plant does not tolerate waterlogged soils, and it is essential to ensure adequate drainage. Mulching the soil can help retain moisture while regulating soil temperature and preventing weed growth.
Indigofera costata subsp. macra can also tolerate slightly acidic soil conditions, but it does not grow well in highly alkaline soil.
Cultivation Methods
Indigofera costata Guill. & Perr. subsp. macra (E.Mey.) J.B.Gillett is a shrub that grows well in tropical and subtropical regions. It requires well-drained soil that is rich in organic matter and full sun exposure for growth. Propagation can be achieved through seed germination or stem cuttings.
Watering Needs
Indigofera costata Guill. & Perr. subsp. macra (E.Mey.) J.B.Gillett requires regular watering during its growing season, which is typically from spring until fall. The soil should be kept moist, but not waterlogged. Over-watering can result in root rot, so it is important to ensure that there is adequate drainage.
Fertilization
Indigofera costata Guill. & Perr. subsp. macra (E.Mey.) J.B.Gillett responds well to regular fertilization. A balanced fertilizer that is higher in phosphorus and potassium can be used during the growing season. The fertilizer should be applied every two weeks for optimal growth.
Pruning
Indigofera costata Guill. & Perr. subsp. macra (E.Mey.) J.B.Gillett requires regular pruning to maintain its shape and promote the growth of new shoots. Pruning should be carried out in the winter months when the plant is dormant. The dead, diseased or damaged branches should be removed, and the remaining branches should be trimmed to shape the plant. The pruning cut should be made above the leaf node.
Propagation of Indigofera costata subsp. macra
Indigofera costata subsp. macra can be propagated either through seeds or cuttings, with the latter being the preferred method due to the high chances of success. Below are details on each propagation method:
Seeds Propagation
The seeds of Indigofera costata subsp. macra are usually collected from mature fruits. Before planting, it is recommended to scarify the seeds to increase germination rates. Scarification can be done by rubbing the seeds with sandpaper or nicking them with a scalpel or knife. Once the seeds are scarified, they can be soaked in water overnight to further increase germination rates.
The seeds can then be planted in containers or directly in the ground during the warm months. Soil should be well-draining and rich in organic matter. The seeds should be sown 1 cm deep and 10 cm apart. Water should be applied sparingly at first, and once the seedlings develop, it can be gradually increased. It takes about 2-3 weeks for seed germination to occur. After this period, the seedlings require regular watering and fertilization.
Cuttings Propagation
The preferable time to propagate Indigofera costata subsp. macra through cuttings is during the early spring. Cuttings should be taken from healthy and pest-free plants. The cuttings should be about 10 cm long and all the bottom leaves must be removed. A rooting hormone can be applied to the cuttings to increase the chances of success.
The cuttings can be planted directly in the ground or in containers, with a well-draining soil mix. It is best to place the containers in a warm and partially shaded area, to encourage root development. The cuttings should be watered frequently but not excessively.
After several weeks, roots should start to develop, and signs of new growth will start to appear. Once this occurs, it is possible to transplant the Indigofera costata subsp. macra cuttings into their permanent location.
Disease Management
Indigofera costata subsp. macra is susceptible to various diseases, including:
- Root Rot: This is caused by the fungus Rhizoctonia solani, which attacks the plant's root system, leading to wilted leaves, stunted growth, and eventually death. To manage root rot, avoid overwatering, plant in well-draining soils, and apply fungicides.
- Leaf Spot: This is caused by the fungus Cercospora spp. and appears as circular or irregular spots on leaves, with a yellow halo around them. To manage leaf spots, remove infected leaves, avoid overhead watering, and apply fungicides.
- Powdery Mildew: This disease is caused by the fungus Erysiphe cichoracearum, which creates a white powdery layer on leaves. To manage powdery mildew, prune infected leaves, plant in areas with good air circulation, and apply fungicides.
Pest Management
Indigofera costata subsp. macra is also susceptible to various pests, including:
- Aphids: These are small insects that suck sap from the plant's leaves, causing them to wither and yellow. To manage aphids, spray the plant with neem oil, insecticidal soap, or pyrethrin.
- Leafhoppers: These insects suck sap from leaves, causing them to yellow and become distorted. To manage leafhoppers, pluck off infested leaves, plant beneficial insect-attracting plants, and apply insecticides.
- Caterpillars: These are the larvae of moths and butterflies that feed on the plant's leaves, causing them to become skeletonized. To manage caterpillars, manually remove them from the plant, encourage natural predators like birds and parasitic wasps, and apply Bacillus thuringiensis (Bt).
