Origin
Derris nobilis Welw. ex Baker is a plant species in the bean family, Fabaceae. It is native to Angola, Cameroon, Central African Republic, Congo, Equatorial Guinea, Gabon, and Zaire in Africa.
Common Names
The plant is commonly known as 'Black Wattle' in English, 'Gralho-amarelo' in Portuguese and 'Mabwe' in Swahili.
Uses
The plant has a variety of uses. Its bark contains tannins which can be used for tanning leather. The wood is durable and can be used for construction, furniture and firewood. The plant has also been used in traditional medicine to treat a wide variety of ailments such as fever, dysentery and snake bites. The plant also serves as a host for insect species, and it is sometimes used as a shade tree in coffee plantations.
General Appearance
Derris nobilis is an evergreen tree that can grow up to 30 meters tall. It has a dense, round crown and a straight trunk covered in a thick, dark bark. The leaves are pinnate, with 8-16 leaflets, and are arranged alternately on the stem. The flowers are small, white, and fragrant, and typically bloom in the spring. The fruit is a pod, which contains several of the plant's seeds.
Light Requirements
Derris nobilis requires ample amounts of sunlight to grow properly. It thrives well in bright to medium indirect light. It is, however, important to keep it away from excessive direct sunlight as it can scorch its leaves.
Temperature Requirements
The ideal temperature range for Derris nobilis is between 18°C and 24°C. It can tolerate a minimum temperature of 13°C and a maximum temperature of 32°C. It is important to keep it away from extreme temperature fluctuations and cold drafts which can cause damage to the plant.
Soil Requirements
Derris nobilis prefers well-draining, nutrient-rich soil with a pH range of 5.5 to 7.0. It grows best in a soil mixture that is rich in organic materials such as peat moss, compost, or well-rotted manure. The soil should also be airy and loose to allow for proper drainage and root development.
Cultivation Methods
Derris nobilis Welw. ex Baker, commonly known as the African derris, is a hardy plant that thrives in warm and humid conditions. It can be propagated by cuttings or seeds. The best time to plant cuttings is during the rainy season when the soil is moist. Prepare the soil by adding compost or manure to enhance its fertility. The plant prefers well-drained soils that are rich in organic matter.
Watering Needs
Water is critical for the growth and development of Derris nobilis Welw. ex Baker. The plant requires frequent watering, especially during the dry season. Water should be applied at the base of the plant to avoid wetting the foliage. However, excessive watering should be avoided as it can lead to waterlogging, which can cause root rot.
Fertilization
Fertilization is crucial for the growth and development of Derris nobilis Welw. ex Baker. The plant requires regular application of a balanced fertilizer, especially during the growing season. A slow-release fertilizer can be applied every three months to provide a steady supply of nutrients. However, over-fertilization should be avoided as it can lead to the accumulation of salts in the soil, which can harm the plant.
Pruning
Pruning is an essential part of caring for Derris nobilis Welw. ex Baker. The plant requires regular pruning to remove dead or diseased branches and to shape its growth. Pruning should be done during the dormant season when the plant is not actively growing. Sterilized pruning tools should be used to prevent the spread of diseases. After pruning, apply a fungicide to prevent the entry of pathogens through the cut branches.
Propagation of Derris nobilis Welw. ex Baker
Derris nobilis Welw. ex Baker, commonly known as "Tanzanian Derris," is a leguminous plant that is native to tropical Africa. It belongs to the Fabaceae family and has a range of uses, including as a source of insecticidal and piscicidal compounds.
Propagating Derris nobilis Welw. ex Baker can be done through various methods, including seed propagation, hardwood cuttings, and stem cuttings.
Seed propagation
Seed propagation of Derris nobilis Welw. ex Baker is the most commonly used method. Fresh seeds that have been recently collected from mature pods have the highest germination rates. Seeds need to be scarified, which involves nicking them with a sharp knife or sanding them lightly to help speed up germination. Germination can take up to two months, and seeds should be planted in well-draining soil at a depth of about 3-4 cm.
Hardwood cuttings
Hardwood cuttings are taken from mature, woody stems during the dormant season. The cuttings should be about 15-20 cm long and taken from healthy, disease-free plants. Cuttings should be treated with rooting hormone and planted in well-draining soil, with only about 2-3 buds above the surface. It is best to keep the soil moist and the cuttings in a sheltered, shady area until new growth appears.
Stem cuttings
Stem cuttings are taken during the growing season when the plant is actively growing. Cuttings should be about 10-15 cm long and taken from a healthy and disease-free plant. They should be treated with rooting hormone and planted in well-draining soil, with only about 2-3 buds above the surface. It is best to keep the soil moist and the cuttings in a sheltered, shady area until new growth appears.
Overall, Derris nobilis Welw. ex Baker can be propagated through various methods. Seed propagation is the most common method, while hardwood and stem cuttings can also be used as successful alternatives.
Disease Management for Derris nobilis Welw. ex Baker
Derris nobilis Welw. ex Baker is a plant that is susceptible to various diseases. One of the most common diseases that can affect this plant is leaf spot, which is caused by fungi such as Cercospora spp. and Phyllosticta spp. The symptoms of this disease are brown spots on the leaves which can lead to defoliation. To manage the leaf spot, it is advisable to remove and destroy the infected leaves. Ensure that the plant has proper air circulation and avoid overhead watering. Fungicides can be used in severe cases.
Another disease that can affect Derris nobilis Welw. ex Baker is powdery mildew, which is caused by fungi belonging to the Erysiphaceae family. The symptoms of this disease include white powdery spots on the leaves and stems of the plant. To control powdery mildew, ensure that the plant is in a location with good air circulation, keep the foliage dry, and remove and destroy infected plant parts. Fungicides can also be used for severe cases.
Pest Management for Derris nobilis Welw. ex Baker
There are several pests that can be a problem for Derris nobilis Welw. ex Baker. One common pest is the spider mite, which can cause yellow and bronze stippling on the leaves and webs on the plant. To manage spider mites, spray the plant with water to dislodge them and provide proper air circulation. Insecticidal soap or miticides can be used for severe cases.
Another pest that can be troublesome is the whitefly, which causes yellowing of the leaves and a sticky residue on the plant. To manage whiteflies, use yellow sticky traps to control the population and remove infected plant parts. Insecticidal soap, neem oil, or other insecticides can be used for severe cases.
Lastly, the stem borer can be a problem for Derris nobilis Welw. ex Baker, causing wilted leaves and stem damage. To manage stem borers, remove and destroy infected plant parts and avoid excess nitrogen fertilization. In severe cases, insecticides can be used.
