Though ECHO has shared information about living fences for many years, we had not written about them in EDN. This information is also available as a Technical Note, with the addition of an extensive list of plant species that have potential as living fences.
Fences are established on the small farm for a variety of reasons. They are used to mark boundary lines between farms or next to roads, and to separate adjacent fields used for distinct purposes. Fences are used to protect and keep animals from straying (to keep animals ‘in’), or to protect crops from animal damage (to keep animals ‘out’). Living fences are commonly used in a wide range of ecological situations, from semi-arid to rainforest conditions. Suitable plant materials are available for almost all ecological regions and conditions.
Very long fences are usually constructed of poles with wire strung between them. Shorter fences, such as those used for fencing small animals or kitchen gardens, may be constructed entirely of wood, or of a combination of materials, such as poles, slats, and woven or welded wire. Both types of fences may be constructed of living posts.
Benefits of a Living Fence
A living fence shares many of the benefits of a manufactured or “dead” fence. However, for the small farmer a living fence provides additional benefits. For instance, living fences comprised of well-adapted plant species are not bothered by termites, carpenter ants and dry rot, which are a continual battle in maintaining “dead,” wooden fence posts.
Fuel. As a general rule, firewood or charcoal is the primary cooking fuel in developing countries. A living fence post can be trimmed periodically and the branches used as fuel. A convenient source of firewood near the farm home, such as a living fence, is especially beneficial in areas where wood is scarce. Extra firewood may be sold or bartered.
Fertilizer. Living fences provide fertilizer in several ways. First, leaves that fall naturally from the tree, as well as leaves and small branches cut away when the tree is harvested for fuel, can be (1) composted, (2) immediately mixed with the soil as green manure fertilizer, or (3) left on the ground as leaf litter mulch. Second, because trees are deep-rooted, they have access to mineral nutrients in soil that may be too deep for shallow-rooted, annual crops to access. After residues from trees decompose, such minerals are released into the soil and become available to crop plants. Third, nitrogen is always difficult and costly to obtain. Leguminous trees are an important source of nitrogen for the small farmer, adding significant amounts of nitrogen to the soil. Finally, pruning of trees results in partial die back of roots, releasing additional nutrients directly into the soil.
Forage. The leaves of many living fence species, such as those of moringa, gumbo limbo and erythrina, are nutritious forage for small animals. The suitability of leaves as feed varies both from species to species and with age. When living fence posts are used to produce forage, space is conserved on the farm.
Food. Leaves, flowers, fruits and seeds of many living fence species are important for human consumption. For example, the flowers of izote or moringa; fruit of cactus, mombin or mulberry; leaves and roots of cassava; and seeds of annatto and cashew are useful in producing food for family use and for market.
Fiber. A few living fence plants, such as the sisal plant and some bamboo species, yield branches or leaves that can be processed into useful fiber for cloth or rope, or used directly for tying.
Shade. Many living fence posts can grow to become shade trees. Trees such as Inga, Erythrina and Ficus species provide welcome relief from the hot sun for people and livestock.
Construction Materials. Many trees are harvested for their wood. Although the farmer wouldn’t be expected to cut down his fence to market the timber, branches from species such as willow can be used for making home craftwork like woven baskets and carvings.
Medicine. Some living fence plant species are also used in medicinal preparations. Jatropha produces a medicinal oil in the seeds. Gliricidia produces rotenone, an effective rat poison, in the bark.
Windbreaks. In some areas, windbreaks are necessary to protect against the drying and lodging action of winds that can damage crops.
Cautions to be Aware of with Living Fences
Whether or not living fences are used on a farm will depend on the balance of the advantages versus the disadvantages. A few cautions to consider are:
- A living fence’s canopy and roots can compete with crops for available sunlight, water and soil nutrients. The extent to which this happens depends on factors such as the species used and pruning height.
- Certain living fence species are readily eaten and destroyed by livestock, or may be invasive.
- Living fences must be carefully selected, maintained and managed.
A fence represents a major investment on the small farm. Using live plant material for posts, or for the entire fence, can increase the return on investment by providing the many secondary benefits and by-products already discussed. The cost of plant material for establishing a living fence can be minimized by obtaining seeds and/or cuttings from existing trees or plants. The labor costs can be high initially, as seeds or cuttings must be planted densely and/or over great distances. Species that produce large amounts of biomass will also require frequent pruning. Since living posts last longer than wooden (dead) ones, replacement costs are reduced.
Establishment and Care of Living Fences
In an area where you plan to promote living fences, first try to identify the species of trees already being used as living fences. Also try to determine if any of the native species are suitable for living fences.
A species used as a living fence ideally should have the following characteristics:
- Resilience to cattle browsing or leaning against it.
- Rapid growth from cuttings or seeds.
- Multiple useful properties.
If suitable materials are not locally available, you might consider importing seeds or cuttings. Many species of trees can be suitable for use as living fences. Some of the more commonly recommended species include:
- Bursera simaruba for dry regions.
- Gliricidia sepium for areas of alternating wet and dry.
- Erythrina berteroana or other Erythrina species for wetter areas.
To establish living fences, trees and other plants are typically planted to form one or more of the following: posts, hedges, or a palisade (a fence of closely set stakes). While any tree can be used as a living fence post, many trees would not normally be so used because of size, propagation difficulty, slow growth, adverse characteristics, or inadequate life span. A few large trees used as occasional fence posts are retained for other benefits (e.g. teak as valuable wood; mango for fruit, forage and shade). The majority of species used as living fence posts can be propagated from large woody cuttings, generally the size of the fence post required. However, some exceptionally fast-growing trees are propagated from seed.
Living fence posts are generally used with conventional barbed wire or wire screen. Take care that wire is not strung around the post. As the post grows, the wire will girdle and kill it. It is better to attach the wire with fence staples or nails. Hedges are established using species that spread to rapidly fill the spaces between plants. Hedges are often comprised of thorny species and may or may not be strung with wire. A palisade includes plants carefully placed as close together as necessary to immediately achieve an animal-proof cage or stockade-like fence. Such plants may be propagated from cuttings or offshoots. Some may also be directly seeded in this fashion.
Living fences are seldom fertilized. They are regularly pruned, however, to shape and maintain the fences, to obtain new planting material or other products, and to eliminate excess foliage. Pruning is a seasonal task, usually done during the dry season, but may also be done every four to six months or as needed. Fences can also be shaped by weaving and tying branches as desired. Insects and disease are seldom a problem with living fences.
Species for Living Fences
Only a few select and widely-used species are featured here. Table 1 in ECHO’s Living Fence Technical Note lists many additional species.
Gliricidia sepium, [gliricidia, madre de cacao, madero negro (Nicaragua), mata ratón, quick stick (Jamaica), cacahuate (Philippines), piyon (Haiti)]. This small leguminous tree is well known to farmers throughout the tropics and is so useful that it was given a medal of honor in Honduras. Gliricidia is easily propagated from cuttings or seed, and can be planted as posts, hedges or a palisade. Common at low to medium elevations, the tree prefers medium rainfall and is well adjusted to periodic dry seasons. An older gliricidia fence post will tend to produce large numbers of long, narrow branches, perfect for propagation by cuttings. Branches and trunks root readily, but growth rate is moderate.
When grown as a hedge, gliricidia produces a narrow fence with a broad crown. Its lifetime is almost indefinite. The wood of older trees turns black, very hard and dense, and is used to make many small objects. Animals feed on the foliage, but in fences (posts and hedges) the foliage is often up out of reach. As forage, gliricidia is a useful feed in moderate amounts and should be combined with a variety of other forages. Flowers, buds, and young leaves are often eaten as a cooked vegetable. The bark and dry seeds contain rotenone and are prepared with small grains as a rat poison. Leaf fall occurs during the dry season, and the leaves make valuable mulch. Gliricidia was used in the past as shade for cacao and coffee, but lately farmers have largely used Inga and Erythrina species instead of gliricidia for that purpose. Gliricidia is used as a trellis for black pepper and for vanilla orchids. In a living fence, gliricidia may be pruned every three years, yielding a good quantity of firewood.
Erythrina berteroana, [pito (Colombia), poró de cerca (Costa Rica), machete (Jamaica), elequeme (Nicaragua), gallito (Panama), pernilla de casa (Panama), brikal (Haiti)]. This leguminous tree is small to medium in size, and is commonly used as a living fence post for barbed wire, a support tree for vine crops or shade for coffee and cacao. Erythrina species other than E. berteroana may also be used. The tree is covered with dense foliage that is important in building the soil organic and mineral matter. Because the leaves are not lost during the dry season, this tree is best suited for regions with somewhat more rainfall than is required by gliricidia.
In general, Erythrina species are well suited as living fences (posts, hedges and palisades) as they are easily propagated and can withstand regular pruning. Erythrina species are propagated readily from seed or from cuttings (large or small) and are usually planted where they will be grown. Growth is moderate to rapid, resulting in a narrow fence with a dense crown. After it is pruned, E. berteroana produces a large volume of new growth within three to four weeks. The foliage is attractive to animals and is used as forage for cattle, goats and sheep. Rabbits that are fed the prunings have sometimes shown adverse side effects.
Upon pruning, the tree produces a large amount of useful biomass. A study by CATIE showed that E. berteroana pruned every 12 months produced the most woody biomass, and when pruned every six months produced the most edible leafy biomass. Pruned every four months it produces 30 t (30,000 kg) of edible dry matter per km of fence; pruned every six months it produces 50 t (50,000 kg) per km. The seeds are toxic. Erythrina species are a favorite living fence species in Costa Rica. (Russo, 1993)
Yucca guatemalensis, (formerly Y. elephantipes), [spineless yucca, izote (Latin America), bayonet (Haiti)]. This is one of the most common plants used in living fences in Central America. Large and small cuttings of the straight stem or trunk are planted as a palisade. As they grow, they make a practically impenetrable wall. The tree is easy to propagate, grows slowly and has a long life. The flowers are edible.
Bursera simaruba, [gumbo limbo, indio desnudo, jinote (Latin America), gomye (Haiti)]. Gumbo limbo is especially appropriate for dryer areas where Gliricidia sepium is not well suited. Planted as large posts or smaller palisades, it will root even under dry conditions. The leaves are used as forage. Gumbo limbo otherwise has few other uses, as the wood is soft and the tree is short lived.
Moringa oleifera, [moringa, horseradish or drumstick tree, marango (Nicaragua), benzoliv (Haiti)]. This “perennial vegetable” is one of the most nutritious vegetables in the world. It handles dry seasons well and grows quickly, especially during the first year. It can be planted as a suitable palisade from both seeds and cuttings (the cuttings tend to be straight), or as a living fence post. An AVRDC (World Vegetable Center) fact sheet on moringa suggests a spacing of 1 m or closer for trees established as living fence posts. Trees are pruned at about head height, and the leaves are used as a nutritious fresh or cooked vegetable or for animal feed.
Jatropha curcas, [jatropha, Barbados nut, physic nut, piñón (Latin America), medsin (Haiti)]. This small tree is known mostly for the medicinal oil produced in its large seeds. The oil is also used to make medicinal soap, and is used for lighting. Recently the oil has been found to have qualities suitable for use as a biofuel. For the small farm owner, however, the tree is especially important as a living fence (hedge or palisade). Animals will not browse on the leaves, making jatropha an excellent choice for palisade fences around kitchen gardens where goats and cattle may be a problem. Palisades and hedges may be planted either from cuttings or from seed. The wood is soft, but the tree produces large amounts of biomass for mulch and compost.
Euphorbia lactea, [raket, kandelam (Haiti)]. This cactus surrounds many of the small farms in Haiti. Cory Thede, an agriculturalist working in Haiti, shared the following comments:
“The plant is called raket around here [northern Haiti, near Cap Haitien], I think it was called kandelam (from candelabra cactus) more on LaGonave. It even grows well here in the rainforest conditions, so it grows in all climates of Haiti. It is a good fence. It is good to wear eye protection when cutting since the sap is very irritating, especially to the eyes. Branches are cut and stuffed into minimal holes (depending on the height of the branch; deeper for taller branches, so they don’t fall over) to make a fence. It sprouts and roots easily, since it is so wet here. As it is a succulent plant, it may be planted rather shallow to avoid rotting. With regular trimming it makes a neat hedge. Here they don’t get much maintenance and vines often cover them, but they survive quite a bit of shade. The pineapple relative, pinguin, is the most common living fence here, but cows can eat it. It has nasty spines that go both directions and tend to break off under the skin.”
Some Useful References
Live Fences, The Overstory #38. S.D. Cherry & E.C.M. Fernandez
Agroforestry Guides for Pacific Islands. C.R. Elevitch & K.M. Wilkinson (Eds.). 2000. Permanent Agriculture Resources, Holualoa, Hawaii, USA. Individual sections of the book can be downloaded in pdf format. See especially #5 (Introduction to Integrating Trees into Pacific Island Farm Systems) and #8 (Multipurpose Windbreaks :Design and Species for Pacific Islands).
Grow Your Own Living Fence, Farm Radio International broadcast script