Nursery Techniques

The nursery is a starting point of production of high-quality planting stock, which is essential for the success of all forest restoration projects.

Mr. Phairote and Mr. Chotgun, members of Ban Mae Sa's community environmental conservation group working at the Ban Mae Sa nursery. Courtesy and Copyright © Anthony BouchSeedlings of all tree species must be grown to a suitable size, must be robust, growing vigorously and disease-free when the season is optimum for tree planting. This is difficult to achieve when growing a large number of different native tree species, which will fruit at different times and vary greatly in their germination and seedling growth rates. Therefore, nursery techniques are high precedence for seedling production and improved tree propagation methods, leading to the development of detailed production schedules for each species being propagated.

Building a nursery

A nursery must provide the condition for the growth of seedlings and must protect them from stress and extreme climates. It must also be a comfortable and safe place for the nursery staff. The size of the nursery depends on the size of the area to be restored, which in turn determines how many trees must be produced each year. Building a nursery need not be costly. Locally available materials, for example, recycled wood, bamboo, and palm leaves can be used to build a simple nursery. Furthermore, simple inexpensive equipment, such as shovels, trowels, watering cans, secateurs, etc., can generate good quality seedlings.

Extracting Sapindus rarak seed. Courtesy and Copyright © Anthony Bouch

Collecting and handling tree seeds

In the nursery, dormancy of seeds prolongs tree production time. Therefore, various treatments should be applied to shorten dormancy. For example, a thick seed coat will be broken dormancy by scarification technique (cutting a small piece of seed coat or rubbing seed with sandpaper for small seed). For species with mechanical dormancy, acid treatment is recommended. For chemical inhibited dormancy, complete removing of fruit pulp and repeated soaking are recommended. Seed sowing needs to use a germination tray filled with a suitable medium (good aeration, drainage, and support). Seed trays should be deep enough and have drainage holes in the bottom.Seedling potting at the Ban Mae Sa nursery. Courtesy and Copyright © Anthony Bouch

Potting

The containers must be large enough for a good root system and support adequate shoot growth. They must have sufficient holes to permit good drainage, and be lightweight, inexpensive, durable, and readily available. Plastic bags are probably commonly used containers. The optimum size is 23 x 6.5 cm., which allows the root to a reasonable length before they reach the bottom of the bags and begin to spiral. The potting medium consists of coarse and fine soil particles with pores between them that allow aeration and drainage, provide growing trees with support, moisture, oxygen, nutrients, and symbiotic micro-organisms. A standard medium should consist of 50% forest topsoil mixed with 25% fine organic matter ad 25% coarse organic matter. Seedlings are ready for picking out when the first 1-3 pairs of true leaves have fully expanded, then transfer seedlings into the containers. The medium within plastic bags should not be compact, but neither should it be too loose. The bags should be up straight, be placed, and water in a shaded area.

Caring for trees in the nursery

Watering seedlings in nurseries depend on the season. During the rainy season, the seedling still alive without water for a few days in open nurseries. By contrast, in the dry season, it may be necessary to water the seedlings twice a day. Fertilizer should be applied to accelerate growth to ensure that the plants are ready for transportation by the planting season. Furthermore, grading is an effective method of quality control. It involves arranging the growing trees to of size, while at the same time removing stunted, root pruning, disease inspection part and shoot pruning. Fast-growing species should not be too large or too cumbersome to handle and easily broken during transportation and planting. However, never prune root and shoots in the month before planting out. About 2 months before planting, gradually reduce the shade and frequency of watering. It would prepare saplings for difficult transitions from environmental in the nursery to the harsh conditions of deforested sites, this technique is called hardening-off.

Production schedules

Different species fruit in different months and have widely different rates of germination and seedling growth, anyway, all species must be ready for planting by the optimal planting time. Species production schedules make this daunting managerial task easier. The production schedule is a concise description of the procedure to produce planting stock of optimum size and quality from seed, wildlings, or cuttings by the optimum planting-out time. It can be represented as an annotated time-line diagram that shows: i) when each operation should be performed, ii) which treatments should be applied to manipulate seed germination and seedling or sapling growth. Species production schedules are an excellent tool to ensure that the species are ready for planting when required.