|Special Public Works Programmes - SPWP - Planting Trees - An Illustrated Technical Guide and Training Manual (ILO - UNDP, 1993, 190 p.)|
|3. Handling seedlings|
The time between the seedlings, leaving nursery and their being planted should be as short as possible. They must be constantly protected from strong light, heat and drying out. There are small root hairs that will dry out and wither in seconds if left exposed to the sun or dry winds. The seedling should be thoroughly watered before leaving the nursery. This will provide the seedling with the largest possible reserve of water and minimize the risk of soil being shaken out of the pots during transport.
Only the containers should be held when containerized seedlings are carried. Seedlings should never be held by the shoots. Whenever possible, use boxes for transport.
Metal platforms of vehicles often get very hot, and this will burn the root tips at the bottom of the pots. Pour water over the platform and/or spread out soil, straw or twigs. It is especially important to put a thick layer over the exhaust pipe otherwise the heat may destroy some of the seedlings. If the seedlings are loaded onto carts, pickups or trucks, load densely and upright. Make sure that they do not fall over during the transport. If necessary, water the plants on the arrival at the planting site.
If a vehicle is carrying the plants, it should travel at moderate speed and the plants should be covered by a layer of grass, a mat or a tarpaulin to prevent them from being dried out by the wind.
Transport from the nursery to the planting site is often a limiting factor, slowing the progress of the planting work. Simple metal structures with several shelves, as shown in the illustration on the preceding page, can multiply the capacity of trucks and trailers several fold.
Packing and transport of seedlings
Water seedlings before they leave the nursery
Never pull by the shoots
Use trays and boxes for transport
Spread straw or twigs
Cover plants with a mat
Bare-rooted seedlings have to be packaged in order for the roots to be well protected from drying out. Sacking, banana leaves, plastic bags with ventilation holes or cans may be used for packing and wrapping. To preserve moisture, the roots can be covered with wet grass, leaves, sawdust or a mixture of water and clay.
If the seedlings have to be stored a few days before planting, keep them in a dark and cool place, a cool cellar or elsewhere in the shade. If bare-rooted seedlings are packed in bags, the bags should not be opened.
Bare-rooted seedlings which cannot be planted in a few days must be healed-in close to the planting site to minimize later transport. "Healing-in" means temporarily putting bare-rooted seedlings in moist soil, under shade, until they can be used for planting. Healing-in should be avoided but it may sometimes be necessary.
Polyethylene bag with ventilation holes
Dig a trench under a shade tree in loose, well drained, but moist soil.
Separate the seedlings from the bundles. On one side of the trench, which should be slightly sloping, arrange the seedlings individually in upright position. Cover the roots with soil taken from the opposite side of the trench, thus making room for the next row of seedlings. The roots should be covered up to, or a little above, the root collar. Firm the soil with the hands. Then place the next row of seedlings. During dry weather the seedlings have to be watered. If the location is not very shady, the seedlings should be covered by brush to discourage the emergence of shoots.
1. Dig a trench in the shade
2. Arrange the seedlings
3. Cover the roots with soil
4. Firm the soil
5. Place the next row of seedlings
6. Several rows of seedlings placed and covered with soil
You should only use seedlings of good quality. Never use seedlings left over from the year or the planting season before. Replacement is much more expensive than seedling production.
Seedlings of good quality have:
- a shoot between one or two times the length of the root (or the pot);
- a sturdy, woody stem with a strong root collar;
- a symmetrical, dense crown;
- a root system with many thin roots in addition to the tap root;
- no signs of fungus or insect attack.
Seedlings of inferior quality should never leave the nursery. If they have, they should be rejected at planting stage. If the plantation site is varied, it may be useful to separate the plants into two or three quality classes. The best plants should be used on the most difficult or inaccessible part of the site. Second quality plants should be used on the more favourable part of the site where replacement planting is less costly.
With tall, broadleaved species, young shoots and part of the foliage must be trimmed or stripped off to reduce transpiration until the roots have had a chance to reestablish their water supply function. Some species such as Azidirachta indica and Khaya senegalensis should be stripped of all leaves except for the terminal bud and two or three near it. Remove the leaves carefully. The terminal bud must not be damaged. If possible the plants should be stripped in the nursery before lifting out.
Overgrown seedlings of some broadleaved species like Eucalyptus can be trimmed back to the right root: shoot ratio with a pruning shear. After planting they survive much better than seedlings that are too large.
Good quality plant
Root: shoot ratio 1:1 to 1:2
¬ Symmetrical dense crown
¬ Woody stem with strong root collar
¬ Dense root system
3rd class not to be planted
Seedlings often have to be transported from the road to the planting site by pack animal or man. Since this is hard work, pack animals are preferable. The total weight to be carried during one day is considerable. In places where roads are sparse the seedlings may have to be transported long distances. If the planting site is large, a number of small deposit points should be set up so that hand carrying can be kept to a minimum.
Tools required for transporting seedlings
A back-pack model seedling carrier is preferable if seedlings have to be carried over long distances, and particularly when the terrain is steep and rough. These may be constructed from traditional baskets and can be used for both bare-rooted and containerized seedlings.
For bare-rooted seedlings there is one model where the seedlings are laid down with the roots toward the middle and secured with a cloth.
When seedlings are delivered in light-weight trays, a carrier on which the trays can be fastened is preferable. Wooden trays are heavy and should only be carried relatively short distances.
Yokes are less convenient than backpacks, but it is still far easier to use one than to carry the plants with ones arms. Yokes are sticks of a suitable shape put across the shoulders. The load is suspended on strings at each end.
for containerized seedlings
for bare-rooted seedlings
Common mistakes in handling seedlings
Poor planting stock is not sorted out leading to low survival.
The seedlings are pulled by the shoots, thereby breaking them and causing deformation of the future trees.
Containerized seedlings are not transported upright and well secured. The earth-balls around the roots break up and therefore the advantage of using an expensive containerized seedling is lost at the last moment.
Seedlings are stored too long before planting.
Seedlings are not adequately protected against drying out.