HOW TO GROW INDIGENOUS TREES FOR REFORESTATION, LANDSCAPING, PLEASURE AND PROFIT.
|Editorial team: Deni Bown, Margrett Jacob, Kunle Olasupo, Femi Olubodun, Taiwo Bankole.| |Photography by Deni Bown and Femi Olubodun.| |Searchable……Downloadable…….Free, subject to Creative Commons Licensing.|
The problem…. Nigeria has one of the highest rates of deforestation in the world and forest cover is now down to 4%. As a result of forest clearance, illegal logging and habitat degradation, many tree species are in rapid decline. This has a serious impact on biodiversity and ecosystem services, and it represents a huge loss of resources for the people and economy of Nigeria. Since the dawn of time, indigenous trees have regenerated naturally. Now many of them need our help or they may soon be locally extinct.
The solution…. To address the crisis the IITA Forest Unit partnered with Botanic Gardens Conservation International/Global Trees Campaign on a project funded by the Mohammed bin Zayed Species Conservation Fund from November 2015 to May 2017 to prioritise and protect Nigeria’s most threatened trees. We collected seeds, tested different methods of propagation, and organised a workshop to raise awareness and encourage interest in tree conservation. A list of 50 threatened trees was compiled, 35 of which are on the International Union for the Conservation of Nature Red List as Near Threatened NT, Vulnerable VU, Endangered EN, or Critically Endangered CR. With support from another donor, the A.P. Leventis Foundation we developed a Tree Heritage Park for the conservation of Nigerian trees (January 2015 – December 2017).
Additional funding for this important work was provided by the Direct Aid Program, Australian High Commission Abuja from January to December 2017 for establishing a centre of excellence and outreach for tree conservation and reforestation in Nigeria . This included compilation of the Manual and upload to a new website. A donation for work on the Manual was also received from the Stanley Smith Horticultural Trust.
Seed collection: To ensure freshness and correct identification, collect fruits directly from the tree. If this is not possible due to the height of the tree, examine fallen fruits carefully for signs of damage before collecting; holes made by insects are often very small and easily missed. Put fruits into paper bags or cartons, clearly labelled with the species’ name and location; avoid polythene bags which encourage decay.
Seed extraction: Separation of seed/s from surrounding tissues to reduce the risk of decay when the seed is sown. Exact method depends on the kind of fruit and is described in the propagation protocol for each species. Fruits of some species do not require extraction as they expose or expel seeds on ripening or, in the case of certain winged seeds, may germinate better if left intact.
Sowing: Placing of seed/s into the growing medium so that they are completely covered (light excluded) or partially covered to admit light. If light requirements are not known and if there are enough seeds, try both methods. The same applies to direction i.e. whether seeds are placed flat or on edge etc. This information is given where known, otherwise try to establish your own protocol by recording exactly what you do and the rate of success.
Pricking out: Removing seedlings from the sowing medium and replanting to give more space and nutrients; this is best done after they develop the first pair of true leaves to avoid damaging the delicate cotyledons.
Hardening off: Gradual exposure of tender young plants to higher levels of light and fluctuations in temperature, wind etc. before planting out. If taken directly from sheltered nursery conditions they may suffer a setback or die from damage to leaves and roots.
Planting out: Successful transplanting of a seedling to a permanent growing position. This needs careful consideration of light and moisture requirements. For best results observe the species in its natural habitat and choose similar conditions.
Safety precautions when using concentrated sulphuric acid: It is important to wear goggles, nose mask, rubber gloves, and a lab coat, as concentrated H2SO4 can cause serious damage to skin and mucous membranes if spilt, splashed or inhaled. Work close to a supply of running water because if there is an accident, the affected part must be washed quickly and repeatedly.
WHAT DOES THAT MEAN?…….
Aril: Fleshy layer that develops from seed or seed stalk, partly or completely enveloping the seed. It is highly nutritious and attracts animals (often birds) which swallow the seeds, digest the aril, and expel the seeds undamaged and ready to germinate.
CR: Critically endangered.
Cotyledons: seed leaves which emerge after germination and before the first pair of true leaves.
Cured sawdust: sawdust from untreated timber which has been stacked in heaps to allow breakdown of toxic and acidic components.
Forest topsoil: an important medium for propagating rainforest trees as seedlings may depend on mycorrhizal fungi for their development and growth; sterilised soil and potting mixes may inhibit germination. When possible, collect soil from under the parent tree.
LC: Of least concern in terms of conservation.
Leaf mould: a blackish crumbly material consisting largely of decomposed leaves, either collected from the forest floor or made by filling black polythene sacks with dead leaves, sealing, and leaving to decompose.
Marcotting/air layering: a method of plant propagation which encourages a small branch to produce roots. This is done by scraping away a few centimetres of bark, covering the wounded area with a moist medium, such as moss, and enclosing in polythene then binding at each end to retain moisture. When roots have formed, cut the branch from the tree and pot up the plantlet, taking great care not the damage the roots.
NT: Near threatened.
Nursery pot/bag/tray: plastic or polythene containers with holes at the base to allow drainage. Choice of container depends on size and number of seeds. Some tree species produce very large seeds that are best sown singly in pots while others have tiny seeds which may be scattered evenly in a seed tray.
Orthodox: seeds that can withstand drying or chilling for a long period with little or no loss of viability.
Orthotropic: growing along a vertical axis.
Propagules: any part of a plant that can produce a new plant when separated from the parent e.g. seed, cutting, sucker.
Recalcitrant: seeds that lose viability if stored. Tropical rainforest trees which fruit at the start of the rainy season commonly have recalcitrant seeds as they germinate rapidly and have no need for dormancy.
River sand: sand collected from the bed of a stream or river to ensure it contains no salt or other substances that damage seeds and seedlings.
Scarify: scratch or abrade the surface of seed to allow take-up of moisture; this mimics damage to the seed coat when passing through the digestive tract of birds that take grit into their crops to break up food.
Sulphuric acid (H2SO4): concentrated sulphuric acid is used to break down the seed coat, mimicking digestive enzymes of frugivorous animals, such as forest elephants.
Growing trees from seed may be easy or difficult depending on the species. Many have not been propagated before. We are sharing protocols (methods) based on our own experience and conditions. If at first you don’t succeed, try again. The important thing is to record exactly what you do so that if results are good you can repeat them or vice versa.
Contact Us – we welcome questions and feedback so that we can share and improve the Manual.