Overview
Indigastrum costatum (Guill. & Perr.) Schrire subsp. macrum (E.Mey.) Schrire, also known as the blue urn bush, is a perennial plant species belonging to the family Rubiaceae. Its unique blue urn-shaped flowers and striking foliage make it a popular ornamental plant in gardens and parks. In addition, it has several medicinal properties that make it a valuable plant in traditional medicine.
Origin and Distribution
Indigastrum costatum is native to southern and eastern Africa and can be found in various habitats such as savannas, open woodlands, and grasslands. It is widely distributed in South Africa, Zimbabwe, Mozambique, and Swaziland.
Common Names
Indigastrum costatum is commonly known as the blue urn bush, African blue urn, and in Zulu as uMavumbuka.
Appearance
Indigastrum costatum is a multi-stemmed shrub that can grow up to 3 meters tall. It has striking foliage with dark green leaves that are hairy and slightly glossy. The plant produces clusters of blue urn-shaped flowers that are about 2 cm long and bloom from late spring to early summer.
Uses
Indigastrum costatum is a valuable plant in traditional medicine, where various parts of the plant are used to treat various ailments. The roots and bark of the plant are a traditional remedy for fever, dysentery, and stomach complaints. The leaves are used to treat insect bites, bruises, and wounds. The plant's ornamental value also makes it a popular garden plant, with its striking foliage and blue flowers adding color and texture to gardens and parks.
Light Requirements
Indigastrum costatum subsp. macrum requires full sunlight to grow and thrive. It can tolerate partial shade but grows best with at least 6 hours of direct sunlight per day.
Temperature Requirements
This plant grows well in warm temperatures and does not tolerate frost or freezing temperatures. The ideal temperature range for Indigastrum costatum subsp. macrum is between 20°C to 30°C (68°F to 86°F), with a minimum temperature of 10°C (50°F). This makes the plant well-suited to tropical or subtropical climates.
Soil Requirements
Indigastrum costatum subsp. macrum grows best in well-draining soils with a pH range of 6.0 to 7.5. It prefers fertile soils that are rich in organic matter. The plant can tolerate a variety of soil types, including loam, sand, and clay. However, it does require consistent moisture levels and does not tolerate drought conditions.
Cultivation Methods for Indigastrum costatum subsp. macrum
Indigastrum costatum subsp. macrum, commonly referred to as 'blue bean,' is a small tree or tall shrub that thrives in tropical and subtropical regions. It is important to plant the blue bean in well-draining soils, preferably loamy or sandy soils mixed with some organic matter.
The plant prefers full sun but tolerates partial shade. Ideally, the blue bean should be planted during the warmer months of the year to reduce the risk of cold damage.
Watering Needs for Indigastrum costatum subsp. macrum
Blue bean plants thrive in well-draining soils that do not retain excess water. Water the plant regularly, especially during the growing season to ensure that the soil remains moist but not waterlogged.
During the dry season, you may need to water the plant more frequently, ensuring that the water penetrates the soil deeply, and the roots have access to the moisture.
Fertilization of Indigastrum costatum subsp. macrum
Applying a slow-release fertilizer, rich in phosphorus and potassium, during the growing season will encourage healthy growth and flowering. Avoid fertilizing the plant during the dormant season when growth is minimal.
Organic matter such as mulch can also be added to the soil to improve moisture retention, soil structure and provide nutrients for the plant.
Pruning of Indigastrum costatum subsp. macrum
Pruning the plant is important to manage its shape, promote healthy growth, and reduce the risk of disease. You can prune the tree in the early spring before the onset of the growing season.
Remove any dead or damaged branches, crossing branches, and branches that are growing towards the center of the tree. You can also prune the tree to maintain a specific shape and size. Keep in mind to use sterile pruning equipment to minimize the risk of introducing infections to the tree.
Propagation of Indigastrum costatum subsp. macrum
Indigastrum costatum subsp. macrum can be propagated by seeds and stem cuttings.
Propagation by Seeds
Seeds of Indigastrum costatum subsp. macrum is harvested from matured pods. The seeds should be soaked in water overnight before planting to soften the outer coat. Sow the seeds in a well-draining potting mixture and cover it lightly with soil. Keep the soil moist but not waterlogged. Germination usually occurs within three weeks. Once the seedlings have grown to a significant height, they can be transplanted into individual pots or to the garden.
Propagation by Stem Cuttings
Stem cuttings of Indigastrum costatum subsp. macrum should be taken from the matured stems of the plant. The cuttings should be at least 4 inches long with a minimum of three leaves on each stem. Remove the leaves from the bottom of the stem and dip the cut end into a rooting hormone. Plant the cutting in a well-draining potting mixture and cover it with a plastic bag to increase humidity around the cutting. Place the pot in a bright, indirect light and keep the soil moist. Roots usually develop within two to three weeks.
Disease and Pest Management for Indigastrum costatum (Guill. & Perr.) Schrire subsp. macrum (E.Mey.) Schrire
Indigastrum costatum (Guill. & Perr.) Schrire subsp. macrum (E.Mey.) Schrire is a beautiful and hardy plant that graces many gardens and landscapes. However, it can be susceptible to a variety of diseases and pests, which can cause significant damage to the plant. Therefore, it is important to follow proper disease and pest management measures to keep the plant healthy and thriving. Below are common diseases and pests that might affect the plant and suggestions on how to manage them.
Common Diseases
Leaf Spot Disease: This is caused by the fungus Cercospora sp. Symptoms include the presence of brown or black spots on the leaves, which usually begin at the base of the plant and progress upward. To manage this disease, it is recommended to remove and destroy infected leaves, improve air circulation around the plant, and avoid overhead watering.
Anthracnose Disease: This is caused by the fungus Colletotrichum sp. Symptoms include circular and sunken spots on the leaves, which may have reddish-brown margins. The spots may also appear on flowers and stems. To control this disease, it is recommended to prune and destroy infected plant parts, improve air circulation, and avoid overhead watering.
Root Rot Disease: This is caused by the fungi Phytophthora cinnamomi and Pythium sp. Symptoms include wilting, yellowing, or browning of the leaves, which are followed by the death of the plant. To manage this disease, it is recommended to avoid overwatering, provide good drainage, and remove and destroy infected plants.
Common Pests
Spider Mites: These are tiny arachnids that suck the sap from the leaves, causing them to become yellow and wilted. To control spider mites, it is recommended to spray the plant with a stream of water to dislodge them, apply insecticidal soap or neem oil, and improve air circulation around the plant.
Aphids: These are small, soft-bodied insects that suck the sap from the leaves, causing them to become distorted and stunted. To control aphids, it is recommended to spray the plant with a stream of water to dislodge them, apply insecticidal soap or neem oil, and introduce natural predators such as ladybugs into the garden.
Scale Insects: These are small, round insects that suck the sap from the leaves, causing them to become yellow and wilted. To control scale insects, it is recommended to apply horticultural oil or insecticidal soap to the plant, prune and destroy heavily infested plant parts, and introduce natural predators such as ladybugs into the garden.
