10. SEEDS

10.5 Local seed collection

Advantages

Local collection of seeds has the following advantages:

• There is no provenance problem with indigenous trees since seeds are collected locally

• Seeds of the desired species are available at the right time; no dependency on other people

• The method is cheap both for the government and for farmers; little expense for transport of seeds

• This is the only possible way for seeds that cannot be stored even for a short period, e.g. Bridelia micrantha and Syzygium spp.

It is not difficult to collect seed locally. It is simply necessary to observe the flowering and fruiting of the desired species so that you can get to know when mature seed are available. It is good to take notes on this and to keep the notes for use in future years.

Timing

When seeds appear to mature it is good to check the inside of the seed (the seed aril). Using common sense is often enough to determine if the seed is mature or not. For most species the seed aril should be hard and white. If the aril is still soft and wet it is better to wait and check again a few days later.

Seeds of certain species, e.g. Combretum and Terminalia spp., appear to be ripe long before they are ready for collection since they turn brown very early. Another way of telling whether the seed is mature or not is to test the dryness of the seed cover. Immature seed, e.g. of Combretum, are moist and soft as compared to mature seed which are hard and dry. Species with edible fruit can be tasted. If the fruit is ripe the seed is also ready for collection. In certain Acacia spp., e.g. Acacia Senegal, seed are best collected before they have fully matured and dried. The best time is when the seed coat is still pale in colour and relatively soft and the swollen pods are just beginning to turn brown. In this way insect damage is minimized and germination is good even without pre-sowing treatment.

A brown, black or dust-like aril is normally a sign that the seed is damaged. Insect holes can also be spotted on the seed surface, occasionally large and easily seen as on Acacia and Albizia spp., but sometimes very small and difficult to see as on Terminalia spp. Insect damage can be very local. If damaged seeds are found on one tree, it may be worth trying other trees some distance away since they may have escaped damage. This applies to Croton macrostachyus, Terminalia and Albizia spp., for example.

An effective way of gaining experience in this regard is to run small local trials to determine the best times and methods for seed collection. If there is doubt about seed maturity or damage, for example, it is recommended to try a small amount of seed first and to monitor the outcome even if this means a year's delay in giving clear advice to farmers.

Practical hints

The best way of collecting most seeds is to harvest the pods or fruits when they are ripe but before they open and the seeds disperse. Some large and hard-coated seeds and fruits can, however, be collected after they have fallen to the ground. Seeds and fruits should then be collected immediately they have fallen to reduce insect or other damage.

When seeds are collected before they have fallen to the ground, which is recommended as the best practice for most species, several methods can be employed. A simple way is to shake the tree, or branches of the tree, so that the seeds fall down. The same effect can be achieved by beating the tree with a long slender pole, by throwing sticks at the branches, or by climbing the tree.

Figure 10.2 Methods of seed collection

It is helpful to clear the ground below the seed tree of bushes and weeds. Newspapers, polythene sheets or sacks can be placed under the tree so that the seeds fall on them and can be collected easily. If there are branches within reach of the roof rack of a vehicle, for example, seeds can be picked directly from the tree. Climbing the tree or use of a ladder may also be possible. A rope with a weighted end can be thrown over small branches which are then broken off by pulling the two ends of the rope. Branches up to 12 m from the ground can be reached using this method. Of course large branches can be cut using a panga, or the whole tree can be felled in order to get access to seeds, but these are destructive methods and hence not to be recommended if there are other alternatives.

If seed collection is carried out on private land, permission must always be sought from the land owner before any collection starts.

Local seed collection is normally best carried out by the farmers themselves with advice from extension workers. It is recommended that extensionists take on the role of facilitators, helping with exchange of seeds, information on where and how good seeds can be collected, etc.