Origin and Common Names
Pterolobium exosum (J.F.Gmel.) Baker f. is a plant species that belongs to the family Fabaceae and is native to Africa, particularly in eastern and southern regions. It is commonly known as the wing-podded stirrup tree.
General Appearance
The plant is a small to medium-sized deciduous tree that can grow up to 10 meters tall. It has a round and spreading crown with a short trunk that can have a diameter of up to 45 cm at the base. The leaves are green, alternate, and compound with two leaflets that are ovate to elliptic in shape. The flowers are small and white, borne in clusters on axillary and terminal racemes that are up to 17 cm long. The fruits are flat and winged pods that resemble stirrups, hence the common name. The seeds are black, kidney-shaped, and surrounded by a yellow aril.
Uses
The bark, roots, and leaves of the Pterolobium exosum tree are used in traditional medicine to treat various ailments such as diarrhea, fever, and skin infections. Its wood is used for fuel and making traditional drums and carvings. In some areas, the fruit pods are used in cooking to add flavor to soups and stews. The plant is also cultivated for ornamental purposes in gardens and parks due to its attractive flowers and unusual stirrup-shaped pods.
Light Requirements
Pterolobium exosum typically prefers bright indirect light, but it can also tolerate partial shade. Direct sunlight should be avoided as it may cause leaf scorching. A location with bright, filtered sunlight throughout the day is ideal for the optimal growth of this plant.
Temperature Requirements
The plant prefers warm, tropical climates with temperatures ranging between 21°C and 27°C. It can survive in temperatures as low as 10°C, but its growth will be stunted. Temperatures below 4°C can severely damage the plant and should be avoided.
Soil Requirements
Pterolobium exosum requires well-draining soil that is rich in organic matter. The soil pH should range between 5.5 and 7.5, with a preference towards slightly acidic soil. The use of a potting mix that is peat-based or contains perlite and vermiculite is ideal. The plant should be watered regularly, but the soil should not be waterlogged as it can lead to root rot.
Cultivation
Pterolobium exosum, commonly known as Poison leaf, is a drought-tolerant plant that can thrive in most soil types. It prefers well-drained soils and full sun exposure. The plant can be propagated from seeds or cuttings.
Watering Needs
Proper watering is essential for healthy growth of Pterolobium exosum. The plant requires regular watering during the first few months after transplanting to establish the roots. Once established, it can tolerate dry conditions and only needs watering during extended periods of drought.
Fertilization
Fertilization is not a necessity for Pterolobium exosum, but it can benefit from occasional feeding of a slow-release balanced fertilizer during the growing season. Avoid over-fertilizing to prevent excessive growth that may weaken the plant.
Pruning
Pruning is recommended for Pterolobium exosum to control its size and shape and encourage bushier growth. Prune in late winter or early spring before the growing season begins. Remove dead, diseased, or damaged branches, and cut back any overgrown stems to promote branching. Avoid pruning too heavily, as it may affect flowering.
Propagation of Pterolobium exosum (J.F.Gmel.) Baker f.
Propagating Pterolobium exosum can be done through different methods such as:
Seed Propagation
Pterolobium exosum can be propagated through seed. Seeds can be collected from the parent plant and planted in a nursery bed. It is recommended to soak the seeds in warm water for 24 hours to help break their dormancy. Once planted, it is essential to provide proper watering and fertilization to ensure that the seedlings grow to become healthy plants.
Cuttings Propagation
Another method to propagate Pterolobium exosum is through cuttings. Take cuttings that are about 10-15 cm long and remove lower leaves. Dip the cuttings in rooting hormone and push them into a potting mix in a small container. Water the cuttings daily and place them in a warm, humid place. After two to three weeks, the cuttings should start to form roots, and once the roots are thick enough, they can be transplanted into individual containers.
Air Layering Propagation
Pterolobium exosum can also be propagated through air layering, a process that involves rooting a plant while it is still attached to the parent plant. Choose a stem that is healthy and not too woody and cut half-way through the stem. Apply rooting hormone to the area where you have cut and wrap it with moist sphagnum moss and plastic wrap. Ensure that the moss stays moist throughout the process. After a few weeks, roots should start forming, and once they are thick enough, cut the branch below the rooted area, and plant it in a separate container with potting mix.
Disease Management
Pterolobium exosum (J.F.Gmel.) Baker f. is generally considered to be a hardy and disease-resistant plant. However, it may still be susceptible to a few diseases that can affect its growth and development. Here are some common diseases that may affect Pterolobium exosum and ways to manage them:
Leaf Spot
Leaf spot is caused by a fungal infection that presents itself as dark spots on the leaves. To manage this disease, it is important to prune the affected leaves and ensure that the plant is not over-watered. In severe cases, fungicide treatment may be necessary.
Mildew
Mildew is another fungal infection that results in a white powdery substance on the leaves. To prevent mildew, avoid overhead watering and ensure good air circulation around the plant. Fungicide treatment may also be necessary in severe cases.
Pest Management
Like most plants, Pterolobium exosum is also vulnerable to attacks by pests. Here are some common pests that may affect the plant and ways to manage them:
Scale Insects
Scale insects are small, hard-shelled insects that attach themselves to the leaves and stems of the plant. They can be managed by pruning affected areas and applying insecticidal soap or oils.
Aphids
Aphids are tiny insects that suck the sap out of the plant, which can cause stunted growth and curled leaves. They can be managed by spraying the plant with water to dislodge them, using insecticidal soap or oils, or introducing natural predators like ladybugs.
