Description of Olea africana Mill.
Olea africana Mill. is a slow-growing evergreen plant that belongs to the family Oleaceae. It is commonly known as African olive or wild olive and is native to Africa, specifically the eastern and southern regions of the continent.
General Appearance
The plant typically grows up to 10 meters in height, with a straight trunk that has a grey-brown bark that sometimes peels off in thin flakes. The branches are frequently twisted and have a dark green foliage that is leathery and mildly glossy. The small, creamy-white flowers are clustered in axillary inflorescences that bloom in the spring. The plant bears small, fleshy, oval-shaped fruits that ripen to black when mature.
Common Names
Olea africana Mill. is known by several common names including African olive, wild olive, and black ironwood. In Africa, it is known by various indigenous names such as umNquma in Zulu, Mutlhwati in Sotho, and Mutsomo in Shona.
Uses
The plant has several uses, both medicinal and non-medicinal. The fruits and leaves have been traditionally used to treat various ailments such as malaria, coughs, and wounds. The wood is heavy and hard, making it suitable for construction, furniture making, and carving. The plant is also popular as a bonsai tree due to its small size, slow growth rate, and the ability to withstand drought. Furthermore, the plant is believed to have ornamental value and is cultivated for aesthetic purposes in gardens and parks.
Light Requirements
Olea africana Mill. requires ample sunlight for optimal growth. The plant thrives in areas with high levels of light, as low levels of light can result in stunted growth.
Temperature Requirements
The plant adapts well to a wide range of temperatures, although it performs best in warm climates. Olea africana Mill. sustains growth in temperatures ranging from 20°C to 35°C, with an average of 25-30°C. Low temperatures below 10°C can inhibit or stunt the growth of the plant.
Soil Requirements
The plant prefers well-draining, nutrient-rich, and loamy soils. Olea africana Mill. grows best in soils with pH levels ranging from slightly acidic to slightly alkaline, at around 5.0 to 8.0. The plant can tolerate moderately saline soils but does not grow well in water-logged or poorly-drained soils. Adequate soil moisture is necessary for proper growth, but the soil should not be excessively wet.
Cultivation
Olea africana Mill. is commonly known as the African olive tree. It's a drought-tolerant tree that grows well in dry areas and savannah woodlands. The tree is relatively easy to cultivate and can be propagated through seeds, cuttings, and grafting.
Seeds should be planted in well-draining soil in a sunny location. The seeds should be planted at a depth of about two centimeters and spaced 20 to 30 centimeters apart. The soil should be kept moist until the seeds germinate, which usually takes about four weeks.
Cuttings should be taken from the tree during the growing season. They should be about 15 centimeters long and should be dipped in rooting hormone before being planted in well-draining soil. The soil should be kept moist until the cuttings have rooted, which usually takes about four to six weeks.
Grafting should be done in the early spring. The rootstock should be a seedling of Olea europaea, and the scion should be taken from a healthy Olea africana tree. The grafted tree should be kept in a warm, humid place until it begins to grow.
Watering
The African olive tree is drought-tolerant but still requires watering. During the first year, the tree should be watered deeply every two weeks. Once it is established, the tree should be watered only during prolonged drought spells or when the soil dries out completely.
The tree is susceptible to root rot, so it's essential to avoid overwatering. It's best to water the tree early in the morning to allow the foliage to dry off during the day.
Fertilization
The African olive tree doesn't require frequent fertilization. A balanced fertilizer should be applied once a year during the growing season. The fertilizer should be applied around the base of the tree and watered in well.
The tree can also benefit from organic fertilizers such as compost or manure. These should be applied to the soil around the base of the tree in the spring.
Pruning
The African olive tree requires minimal pruning. Dead or damaged branches should be removed as soon as they are noticed. The tree can also be shaped by selectively pruning branches to maintain the desired shape. Heavy pruning should be avoided as it can stimulate excessive growth and weaken the tree.
Pruning should be done during the winter dormant season, as the tree is less susceptible to stress during this time. Pruning should be done using sharp, clean tools to avoid damaging the tree.
Propagation of Olea africana Mill.
Olea africana Mill., often referred to as the Wild Olive tree, can be propagated through several methods including seed propagation and vegetative propagation.
Seed Propagation
Seed propagation is the simplest and most common method of propagating Olea africana Mill. Seeds can be collected from mature fruit after it turns black. The collected seeds should be carefully washed with water to remove all the pulp, then left to dry and stored in a cool, dry place until they are ready to be planted.
Before planting, the seeds need to be scarified to break their hard seed coat to allow water and air to permeate. After scarification, the seeds should be planted in a well-draining soil mixture. The container should be placed in a warm, well-lit area, and watering should be done regularly without allowing the soil to become waterlogged. Germination time can range from several weeks to several months, depending on the climatic conditions.
Vegetative Propagation
Vegetative propagation is another method of propagating Olea africana Mill. and is suitable for those who wish to replicate the exact characteristics of a particular tree. This method involves the use of cuttings from selected trees, which can be propagated through either stem cuttings or root cuttings.
Stem cuttings can be obtained by taking semi-hardwood cuttings from the current season's growth. The cutting should be about 15-20 cm in length and free of leaves and flowers. The lower end of the cutting should be wrapped with moist cotton wool and dipped into a rooting hormone before planting into a well-draining soil mixture. Keep the cuttings moist, by misting with water, and place the container in an area with high humidity and indirect light until the cuttings roots begin to emerge.
Root cuttings are obtained by digging up a young part of the roots of an established tree, cutting them into segments, and planting these segments in a well-draining soil mixture. Because of the importance of sterility in root cutting propagation, it is recommended to use sharp tools, and care should be taken to disinfect them before use. The container should be kept in an area with high humidity and indirect light until the cuttings roots begin to emerge.
Propagation success rate can vary based on various factors such as environmental conditions, level of expertise, and care given to the propagation methods. Generally, propagating Olea africana Mill. through seed propagation is easier and less demanding than vegetative propagation.
Disease and Pest Management for Olea africana Mill.
Olea africana Mill., commonly known as the African olive tree, is a species that is native to Africa. It is a sturdy and resilient plant that is generally resistant to pests and diseases. However, there are still some common pests and diseases that can affect the plant. It is essential to manage these threats to ensure the continued health of the plant.
Common Pests
Olive fruit fly: The olive fruit fly is one of the most prominent pests that can affect the African olive tree. The larvae of this fly damage the fruit, causing it to rot and fall off the tree prematurely. To manage this pest, it is essential to keep the area clean and free of dropped fruit. Additionally, using insecticides can help reduce the populations of this pest.
Olive psyllid: Olive psyllids are sap-sucking insects that can cause significant damage to the leaves of the African olive tree. A heavy infestation can cause leaves to yellow and fall from the tree. To manage this pest, it is essential to use insecticides and to prune away any heavily infested branches from the tree.
Common Diseases
Verticillium Wilt: Verticillium wilt is a fungal disease that affects the African olive tree. This disease can cause leaves to turn yellow and wilt, and it can ultimately lead to the death of the plant. To manage this disease, it is essential to practice good sanitation, removing any infected plant debris from the area. Additionally, using fungicides can help reduce the spread of this disease.
Phytophthora Root Rot: Phytophthora root rot is a fungal disease that can be especially difficult to manage. This disease can cause the roots of the African olive tree to rot, leading to poor growth and plant death. To manage this disease, it is essential to plant the African olive tree in well-draining soil. Applying fungicides can also help reduce the spread of this disease.
Overall, managing pests and diseases for the African olive tree involves taking a proactive approach. By monitoring the plant's health regularly and responding quickly to any signs of trouble, you can help ensure the continued success of this beautiful tree.
