9. TREE PROPAGATION METHOD

9.7 Tree-planting techniques

Time of planting

Tree seedlings are best planted out at the onset of the long rains, i.e. by the beginning of April in most parts of Kenya. In some areas, e.g. in Meru and in north-eastern Kenya, the short rains are preferred, and in those areas the best planting season is November or December. The rains should be well established, and it is recommended that the soil be moist to a depth of at least 20 cm at the time of planting. If after one or two showers only a few centimetres near the surface are wet, the seedlings may easily dry out if those showers are followed by a dry spell. In some areas where the infiltration capacity of the soil is poor it may take a very long time before the upper 20 cm of soil are wet. In such areas it is necessary to loosen the soil by digging and to refill the holes prior to the rain.

Tree planting is best done on a cloudy day. Since this tree planting will coincide with a peak period for other farm work, as much preparation as possible should be made in advance.

Figure 9.11 Planting tree seedlings along a grass strip

Site preparation

A hole 30-40 cm deep and equally wide should be dug for each seedling. In this way, the soil is loosened and the roots can establish easily. The topsoil should be separated from the subsoil, and when the hole is filled up again the topsoil should be put back first since it is usually more fertile and should be near the tree roots. The holes can either be dug at the time of planting or in advance. Digging holes in advance has the advantage that it saves labour during the tree-planting period and if the soil is loosened early it may trap and retain more moisture.

If the soil at the planting site is poor it can be improved with manure, compost or other organic matter.

Figure 9.12 A hole and soil prepared for planting

Care of seedlings

Ideally, seedlings should be about 30 cm high when they are planted out. Smaller seedlings may compete less successfully with weeds, and since their stems are not yet very woody they are easily damaged during transport. An exception to this is the case of wildings which are sometimes planted when they are much smaller. Overgrown seedlings are also easily damaged during handling and may have lost vigour due to many root-pruning operations and a too-small root compared to the shoot. In order to avoid damaging them, seedlings grown in pots should not be carried by the shoot but rather by holding the pot.

Figure 9.13 Care of seedlings

If seedlings are raised without containers, care should be taken to retain soil around the roots when the seedlings are planted out. Occasionally this may fail, however, and in such cases it is very important to avoid the roots drying out or being exposed to sunlight.

How to plant

While planting the following points are important:

• After planting, the soil surface should be level with the overall ground level in the nursery, neither deeper, nor higher up.

• If the seedling was grown in a pot, the pot should always be removed. Otherwise the pot may restrict the growth of the roots eventually strangulating the seedling and severely reducing its growth.

• After refilling the hole, pack the soil firmly around the seedling's root mass and make sure that there are no pockets of air in the soil. Water if there is no rain.

• Mulch near the seedling to reduce evaporation of moisture and to suppress weeds.

Figure 9.14 Remove the container before planting the seedling

Application of a small amount of fertilizer or manure will help fruit tree seedlings to get a good start (see Case Report No. 21).

Care after planting

Regularly spot weed around the seedling for at least a year after planting. Weeding reduces competition for nutrients and moisture and dramatically enhances growth.

Protection against livestock trampling and browsing is, of course, important, as is protection against fire during the dry season.

Mulching helps to retain moisture and suppress weeds, but may also attract termites. If termites attack young trees, an application of ash can help. Leaves of neem, Azadirachta indica, also act as termite repellants. If a few valuable seedlings are attacked by scales or aphids, wash them with a strong solution of detergent (e.g. Omo) and water the tree if the soil is dry.

Some species tend to bend or produce many branches in the early stages, e.g. Cordia abyssinica and Acacia spp. Such seedlings may perform better if they are trained up a stake and side pruned.

Figure 9.15 Three of the many ways in which seedlings can be protected