Other uses. Flowers are bee forage. Cooked leaves and flowers are used as a human food. Gliricidia is used to make medicines, rodenticides and insecticides. It is also used as a windbreak and ornamental. Cut boles are used to propagate orchids.
Silviculture
Propagation. This species is easy to propagate by cutting or seed. Large sized cuttings, 1 to 2.5 m in length and 6 cm in diameter, are made from branches 1.5 to 2.0 years old. Small cuttings are 30 to 50 cm long and made from branches 6 to 12 months old. Branches used for cuttings should be straight and healthy, and without side branches. The top of the cutting should be cut on a slant to prevent water collection and subsequent rot. The bark on the lower portion of the cutting should be scarred through to the cambium with a sharp knife to encourage rooting. One-third of small cuttings can be buried. For large cuttings 50 cm is sufficient. Trees established from cuttings will have a shallow root system and a short bole. They are susceptible to uprooting by heavy winds.
Seed is yellow to brown in color with 4,500 to 11,000/kg. Under optimum storage conditions-6 to 10% moisture content at 4? C-seed remains viable for over 10 years (Allison & Simons 1996). At 50% moisture content and 17? C seed can be stored for a year (Hensleigh and Holaway 1988). Seed is sown without pre-treatment directly into nursery containers. Standard nursery management practices are recommended. Seedlings are ready for transplanting after 2 to 3 months in the nursery at a height of 30 cm. Direct sowing is possible with 2 to 3 seeds per planting position at a depth of 1 to 2 cm. Site preparation is required to reduce competition. Direct sowing and transplanting operations should coincide with the rainy season. Seedlings are sensitive to competition. Regular weed control should be practiced until trees are established.
Seed production. There is strong international demand for gliricidia seed. Depending on location and provenance, seed price varies from $2 to $120/kg. Seed shortages, particularly for superior provenances, indicate that seed production may be a rofitable agricultural activity. In Southeast Asia, the International Centre for Research in Agroforestry (ICRAF), Winrock and local collaborators are developing seed production guidelines for farmers.
Pests
Gliricidia is relatively free from insect and disease problems. Boa and Lenn? (1996) provide a list of reported problems.
Symbiosis
Gliricidia sepium fixes atmospheric nitrogen with Rhizobium soil bacteria. If gliricidia is being introduced to a new area or degraded site, seed or plants should be inoculated with the appropriate Rhizobium bacteria before planting. A list of Rhizobium suppliers is available from FACT Net.
Provenances
Growth and yield varies greatly among provenances. The Oxford Forestry Institute (OFI) has conducted extensive trials with 28 provenances. Provenance Retalhuleu (Guatemala) is superior for leaf and wood production, and stem length. Provenance Belan Rivas (Nicaragua) is consistently good for leaf and wood production. Other provenances are appropriate for specific sites or uses (Dunsdon and Simons 1996).
Gliricidia sepium
Last time we introduced you to the Leucaena species. The main attraction this time is Gliricidia sepium. Like the Leucaena, Gliricidia sepium is a specie that is widely used by the New Forests Project. In fact, Gliricidia seeds are especially harvested at our agroforestry training center in Nueva Concepcion, Guatemala and then sent to farmers and local organizations around the world. Although the specie traces its “roots” to Mexico and Central America, Gliricidia now occurs naturally in the West Indies, Africa, and in parts of Asia. Let’s take a closer look at this tree specie and its many uses to understand why this tree has become so popular.
“Quick stick” is a term given to Gliricidia in Jamaica. This name refers to the ease at which this tree can be propagated with cuttings. In laymen’s terms, this means that the tree’s branches (especially tall ones) will quickly develop roots and grow when they are stuck into the ground. (Cool!) As a result, the tree is a favored choice for making live fences, and acts as an excellent barrier against high winds and storms, thereby also helping to control erosion of precious top soils.
And (believe it or not), this is just part of what makes Gliricidia so great. Here are a few more of Gliricidia’s attributes and characteristics:
Nitrogen Fixing Tree (NFT): Like the Leucaena (and all other NFP species), Gliricidia is able to fix nitrogen from the atmosphere. Nitrogen is a vital component for all plants and trees. Normally, plants/trees are able to obtain this nitrogen from the soil. However in many areas, especially in the tropics, soils lack sufficient amounts of this nutrient. Through a special relationship with microorganisms known as rhizobia found in the tree’s root nodules, NFT species are able to convert and use atmospheric nitrogen in the place of soil nitrogen. However, in some cases the rhizobia is either absent or in insufficient quantity to produce enough nitrogen to ensure the tree’s survival. In cases like these, it is possible to add laboratory grown rhizobia cultures to the soil. This process is known as inoculation. In either case, the result is species which can live and thrive on very poor and degraded soils unsuitable for most other types of trees. The Gliricidia in particular, can thrive in dry, moist, or even acidic soils where even the Leucaena cannot.
Fodder/ Forrage: It is the tree’s leaves that retain much of the nitrogen obtained from the atmosphere and thus, when they fall this nitrogen is transferred into the soil. In the long term, this process helps restore and rejuvenate once degraded soils and lands. This foliage can also be used as a natural fertilizer or “green manure”, thereby helping to reduce the use of chemical
fertilizers that are often expensive and environmentally unfriendly. Gliricidia leaves are an excellent source for animal fodder as well. Studies have shown that, on average, Gliricidia leaves contain approx. 25% crude protein.
Alley Cropping: When planted along side food crops, Gliricidia trees provide valuable nutrients, they also help with weed control, and fallen leaves help conserve water and improve soil fertility. Maize, cassava, taro, vanilla, pepper, are just a few crops that are frequently planted alongside Gliricidia.
Last, but not least, the tree is pretty! Once a year, Gliricidia produces a beautiful crown of white and purple flowers.