Overstory #43 - Essentials of Good Planting Stock
Editor's Note
Dear fellow agroforesters, Whether you grow your own trees for your project or purchase them, you are probably aware that the quality of the seedlings is important to the success of the project. But what is a "good quality seedling?" How do you know if the seedlings you grow or purchase are high quality? This Overstory excerpts the original article authored by forestry advisor Norman Jones, and published by the World Bank (ASTAG), and offers advice on the essentials of good planting stock.
Essentials of Good Planting Stock
The extent of the world land base that is being reforested or afforested is significant and is growing still. Unfortunately, several of these efforts are wasted in planting poor quality trees. While some problems are beyond the forester's control--inclement weather, insect attacks, disease outbreaks, animal browse, and the like--others fall within the forester's influence. Two such areas are seed collection, and planting stock preparation and selection. Measures outlined in this bulletin provide basic guidelines that will help the forester ensure a cost-effective means of producing high quality seedlings.
A Measure of Quality
The basic goal of having quality seedlings is to achieve the best growth possible and have the highest amount of desired outputs. Outputs can be timber, food, fuel, fodder or other uses such as site improvement. Seedling quality is gauged by two factors: one, by the genetic make-up of the parent stock and secondly by the physical growth, which is influenced by the seedling's immediate environment (i.e., nursery conditions and practices).
Selection for desirable genetic traits takes place in the field at seed collection sites. When done properly, field selection will provide the best possible seeds, containing the desired inherent traits seen in the parent stock. Care in seed selection and collection will also reduce the amount of undesirable stock coming from physically poor or damaged seed. Aside from genetic traits, a seedling also displays physical traits including sturdiness, good form, health and vigor. Many of these traits, which are affected by nursery practices, are within the forester's control.
Benefits Outweigh Extra Cost, Effort
Nursery-grown stock requires investment in infrastructure, staff training and skilled management. The level of these costs relate to the type of nursery stock produced, species growth responses and the number of trees produced. But, the potential benefits of good nursery practices far outweigh their costs. For instance, properly developed seedlings stand a better chance of survival both in the nursery and when replanted in the field.
In the long term, quality stock will also produce a faster, higher return for the desired outputs. These outputs may include products such as fuelwood, building materials, industrial cellulose, animal fodder, erosion control, and soil and microclimate improvement. Given these benefits, seedling costs are a small portion of the end-product value of plantations. Conversely, slackened efforts at ensuring stock quality will result in lost opportunity throughout the life of the plantation. Low-quality seedlings will experience slow growth after transplanting and add to weeding and maintenance costs. In addition, the trees will be less able to resist disease and insects and will have smaller product yields.
Poor plant quality will result in uneven development throughout the nursery and increase costs through excessive culling needs. In addition, suboptimal quality will increase the risk of losing the seedlings, requiring a renewed effort or, at worse, cancel the project due to lack of adequate seedlings.
Common Principles
Regardless of the size of the tree planting effort, several common techniques can be applied to ensure the best planting stock quality possible. The techniques are applicable across a wide range of climate and soil variations.
The application of good practices must begin when the project, large or small, is planned and must continue through to outplanting in the field. In all cases, everything that can be done, should be done, within reasonable limits of time and capital constraints.
Seeking Optimum Growth
To ensure quality stock, a series of steps must be followed beginning with the planning stages and carrying through to outplanting in the field. Oftentimes foresters or nursery managers focus their efforts on only a few steps of the process. Under such circumstances, nursery stock may still grow. But the omission of any steps will slow the seedlings' progress and produce stock of suboptimum quality.
Such marginal results are unacceptable in light of the time and costs required to produce a forest crop. In fact, the best nursery managers take the trouble to visit field plantations and take pride in the way their plants have responded to the harshness of the real world. To ensure quality stock, a series of steps must be followed, beginning with the planning stages and carrying through to outplanting in the field.
Identifying Weaknesses
Lack of knowledge may be the greatest hindrance to producing consistent quality in growing stock. Indeed, due to the rapidly expanding planting programs, many foresters have never seen a truly high-quality seedling population. Small-scale projects that have minimal resources are particularly vulnerable to lack of proper information for nursery planning, management, operations, and problem solving. Such information voids may be further compounded by inexperienced labor or lack of supervisory skills. Again, because of the lengthy time frame involved between field planting and harvesting, there is little room for error or omission in nurseries.
Producing the Best Possible Plants
The forester must keep the primary objective in mind: to grow the best possible uniform seedlings, for the highest plantation outputs, for the least possible cost. Of course, cost and seedling quality must be carefully balanced. The best plants are derived from consistent nursery practices that produce uniform growth throughout the seedling crop. Such practices include all the elements involved in nursery operations--watering, soil mixes, root pruning, weeding, and the like. The demands of planting schedules alone leave little room for inconsistencies. For example, if seedling growth is not carefully monitored, so that abnormalities can be detected and corrected, seedling development may vary widely.
As a result, some stock may be underdeveloped when planting season arrives and the opportunity for using the stock will be lost. Moreover, it is a fallacy to believe increased watering or fertilization schedules can correct the inadequacies of genetically poor stock that appears underdeveloped. A nursery manager can compound the problem if he keeps these underdeveloped seedlings for later use when "they are big enough." This is wrong. Never plant seedlings which have been held back for extra time.
What Does Good Planting Stock Look Like?
The prime targets are plant uniformity and health. Uniformity means there are few differences from plant to plant in height, stem thickness, the number and relative size of leaves. Health refers to both color and damage. Leaf and stem colors are often characteristic for a species and damage should be easily identified because parts may be eaten by insects or discolored by fungi.
References
For the full version of this article, originally published by the World Bank (ASTAG), including more tips on nursery establishment and management, visit
The author Norman Jones can be reached at 1 Bradfield Avenue, BRIDGEND, Mid-Glam CF31 4HL, United Kingdom; Tel: [44 16560] 656726; Fax: [44 1656] 768369.
Related Editions to The Overstory
- The Overstory #69--Some Tree Basics
- The Overstory #59--Choosing Species for Timber Production and Multiple Benefits
- The Overstory #19--Selected Tree Seed
- The Overstory #5--Start Small