by HENRY I. BALDWIN, Research Forester, New Hampshire Forestry and Recreation Commission, U.S.A.
There is an increasing interest in many countries in the expansion of tree-planting programs. These programs may involve, first of all, small experimental trials of species not yet grown in these countries and, secondly, plans for large-scale afforestation or reforestation programs with species proven by test to be successful for the purposes desired.
1 This article is an extract from a technical study, later to be published, prepared for FAO on collecting, extracting, cleaning, testing, storing and shipping tree seeds, and on practical arrangements for their exchange internationally.
1 See also "Introduction of Exotic Trees - Dangers from Diseases and Insect Pests". J.S. Boyce. Unasylva, Vol. VIII, No. 1.
A plans for obtaining tree seeds must include decisions on the kind and quantities of seed wanted, geographic source and race or variety, and how the seeds are to be collected, extracted, cleaned, tested, stored and shipped. Details of import and export permits, quarantine inspection, and payment can usually be left to the commercial dealer or collector from whom the seeds are to be purchased.
Certain records are necessary in all cases. Certificates of origin and seed quality should be obtained from collectors or dealers, or official seed testing stations, where they exist. Records of special collections need to be made, and should be kept identified with the seeds throughout the course of processing, shipment and ultimate use. To be of any value the records of origin must be maintained when the seeds are sown in the nursery or directly in the field, and for ultimate plantation.
Source of provenance
All forms of life exhibit variation in natural populations, some to a greater degree than others. Evidence of variation in trees of the same species has been accumulating, especially during the present century, so that many different geographical races have been distinguished and generally accepted in hundreds of tree species, and suspected in others. Trees that have a wide range, including areas differing in climate or soil, may quite probably exhibit differences even if these are not apparent. The literature on this subject is very extensive. Data on any given species generally can be obtained from the country of origin.
Many countries and minor subdivisions have special laws or regulations aimed at insuring reliable certificates of provenance. As a result of the Sixth Session of the FAO Conference in 1951, Member Governments agreed to the principle of seed certification, and a standard form was developed. This record of origin should be adequate to provide the information necessary to permit later collections or importations to be duplicated. It should be filled in as completely as possible, and a file maintained of the disposition of each seed lot so that every plantation can be identified with the record.
Certificate of quality
Before purchasing, storing, shipping or sowing any seeds, the viability or capacity of the seeds to germinate and produce plants must be made available. Dead seeds that have lost viability are worthless, and seed lots, only a portion of which are viable, are obviously of less value than where a high percentage is capable of germination. Since seed of low viability requires denser sowing in the seedbed in order to secure a seedling stand of optimum density, the expense of shipping poor seed should be avoided. Knowledge of viability requires testing by some means, preferably tests of germination.
Since seeds are sold by weight and shipping costs depend on weight, freedom from foreign matter such as bark, leaves, cone scales, tree wings and other appendages, and other kinds of seeds is also very desirable, because it affects the value of the seed lot per unit of weight. Moreover, danger of importation of insects and diseases is greatly increased by foreign matter, such as particles of soil. For these reasons, reliable seed dealers use great care to clean seeds.
Germination and purity are the two most important factors in seed quality, and are both commonly determined for seed tests for a certificate of quality. The reputation of a seed dealer depends on such certificates and will often decide his success in obtaining and keeping customers. In the process of purity determination the weight of 1,000 seeds is easily calculated. This is useful since it is a measure not only of the quality of the seed crop of the year but also as a check on origin, as some provenances are characterized by differences in seed weights.
Consignment form
The third record is merely a designation of the sender and destination to which the seed is sent. The sender may or may not be the collector or dealer. This form is for use by the quarantine inspection, postal and transport agencies and customs officials. Its purpose and use are self-evident.
Inspection certificate
Many countries have no import quarantine regulations to protect against introduction of plant pests. Others accept the certification of a foreign government that the seed is free from pests; and still others refuse to accept any certificates but carry out their own disinfection and inspection.
Where inspection service is available to exporters of seed the seed should be so inspected and certified, since entry into the importing country will be thus facilitated. Import permits are required by many countries.
Details of collection methods of various species may be obtained from many texts, pamphlets, and reports published in many countries. These should be consulted before initiating collecting operations. General principles only can be mentioned here. It is necessary to know the location of seed supply, whether a crop is to be expected in the year collection is to be made, and the time of maturity, before arrangements can be made to collect seeds. Transport of the seeds and how they are to be stored, packaged, and protected in the process also require planning.
Locating seed supplies
Seeds are borne only by trees that have sufficient maturity, and in most species there is an optimum age of seed bearing. Crops increase in volume and quality up to a certain age and then fall off with increasing age. Seeds from trees just beginning to bear are often of poor quality. Trees for seed collection should be of good form, if the seeds are destined for timber production, to avoid danger of undesirable genetic qualities. However, open-grown trees produce more abundant seeds and, if adjacent trees in dense stands are of good form, they may safely be used. Similarly, trees whose poor form is due to mechanical injury may also be used.
Unless a region is already well-known, scouting will be the first step, in order to locate stands of sufficient maturity and of a character capable of seed production and having desirable form. In some countries considerable progress has been made in developing and reserving for collection seed orchards of so-called "elite" trees.
Determining abundance of seed crop
Seed crops of trees that require more than one year to mature their fruits may be forecast by observation of the abundance of immature fruits; in others the nature of the flowering earlier in the season can be used as an indication. In any case, examination of the seed collection area in advance of the maturity of the seed crop is necessary. Since many species set really good crops at intervals of several years, seed crop reports over a period of years are valuable in estimating the occurrence of crops.
Estimating maturity of seed crop
Knowledge of the condition of fully mature seeds of the species is essential. Then the average date of maturity in the given region should be known. Appearance of the cones or fruits is helpful but not always reliable. Samples should be examined to see if the seeds are well filled out. Contents of immature seeds are often "milky", the seed coats are soft, or the seeds are not fully grown. Specific gravity tests for the cones of many pines have been found accurate in determining maturity. The seeds of some trees are shed soon after maturity, so that collection should begin early rather than late where the collection period is short. Experience indicates that mistakes are most often made by waiting until too late in the season. Storing by squirrels and other animals is often a good indication of the best time to begin collection.
Methods of collection
When many seeds are borne within a large fruit, or cone in the case of conifers, the entire fruit is usually collected. Small seeds as in birches and poplars may most conveniently be gathered by clipping off small twigs and branches with fruits attached. Large seeds from trees such as oaks and hickories can be gathered from the ground. Collection from standing trees is usually more time-consuming than from the ground or from felled trees, but can often be made from the tops of trees felled in logging operations provided the trees are felled at the proper stage of seed ripeness.
Various tools have been adapted or developed to facilitate cutting cones, fruits and twigs from standing trees. Ladders and climbing irons are also used. Where squirrels and other animals hoard seeds, such caches can sometimes be located and collection greatly simplified. Methods vary in different countries depending on tradition, labor conditions, topography and the nature of the seeds to be gathered. They range from simple hand-picking, often by children, to the elaborate machinery used by commercial walnut-growers.
Special conditions
Harvesting the seed crop is a regular operation in many public forests. Taking seeds from private or public forest lands requires the owner's permission. It is also well to find out if other collectors use the area proposed so as to avoid unfortunate conflicts. Transport of fruits or cones to extracting plants may involve quarantine restrictions to prevent spread of insects and diseases. All these factors should be thoroughly cleared well in advance of the time of collection.
Storage of fruits and cones after collection
Green fruits and cones, especially those of fleshy character, tend to heat or ferment a few hours after gathering if they are kept in compact piles or sacks. They should be kept as cool as possible. Sometimes spreading out on large pieces of canvas is practicable in dry climates. Good aeration is essential. Seeds that cannot withstand drying should of course be protected. Perishable seeds can be packed in the manner in which they are to be stored and thus shipped from the place of collection.
Experience has shown that more consideration should be given to methods of packing tree seeds than has been customary in the past. Loss of viability has been traced to exposure to high temperature and varying humidity in transit. Some seeds require preservation in dry conditions, others moist, but nearly all are unfavorably affected by high temperatures and great changes in temperature.
Temperature
Little can be done to control the temperature during transit, short of refrigeration which is expensive and rarely necessary. Sensitive seeds should be shipped by air whenever possible, since they are less liable to be exposed to heat and are in transit a shorter time. Stowing near steam pipes in ships, railroad trains and warehouses is to be avoided whenever possible. Freezing can injure seeds with high water content. Seeds are, of course, less liable to damage from heat and freezing than other plant parts. Some protection can be given against temperature by insulating packing.
Moisture
Packing can eliminate most if not all danger from moisture changes. Sealed containers and modern plastic materials furnish means of packing seed so that any given moisture condition can be maintained during storage and shipment.
1. Seeds that should be kept dry. This category includes most conifer seeds, stone fruit seeds and many light-seeded species. Many of these keep best when dried to a very low moisture content. It is, therefore, necessary only to dry the seeds to the optimum moisture content and store them in sealed containers. Small samples may be shipped conveniently in strong jute paper envelopes enclosed in larger strong paper envelopes. Packages sent by air are in little danger of encountering high humidity. A better method is to enclose the seed envelope or cloth bag in a bag or wrapping of polyethylene film that is sealed air-tight by use of a hot iron or by closing the mouth of the bag with a stout rubber band. Many such bags are now on the market for use in shipping fruits, vegetables and other plant parts. This plastic film has the advantage of permitting passage of carbon dioxide but not water vapor. Seeds packed in this film have been kept two or three years in a high humidity chamber with practically no increase in moisture content.
Another method consists in enclosing the paper envelope or cloth bag in a wrapping of aluminum foil attached to heavy kraft paper. The foil is coated with a plastic and can be sealed by use of a hot iron; the right temperature must be used.
Very sensitive seeds can be maintained at an accurate moisture content by enclosure in a plastic, glass, or other sealed jar containing beads of silica gel that maintain the seed at a fixed moisture content. The jar can be opened repeatedly without disturbing the moisture equilibrium and seed can be separated from the beads by screening: such containers should be packed in substantial boxes to withstand crushing.
In fact, all large packages of seed should be given outside protection to prevent crushing that might burst the plastic bag or cause mechanical injury to the seed itself. Sometimes a strong cloth bag outside the plastic bag will be enough, but large packages should be boxed and protected by soft packing material which, incidentally, acts as insulation against temperature changes.
Large bags of seeds, 100 pounds (about 45 kilograms) or more, are regularly being shipped from seed dealers in one country to dealers abroad, enclosed simply in an outer canvas or jute bag carefully sewed up. Such shipments appear to travel satisfactorily, but there are often no checks made of the germination before and after shipment. If the moisture content of the seed cannot be controlled at the time of packing, bags permeable to air are probably to be preferred to air-tight covering.
The outside container should in any case be strong enough to withstand rough handling. Thus cardboard cartons and boxes made only of plywood often arrive crushed and broken. Such containers should be reinforced inside with a stout wooden frame.
Small packets should always be enclosed in a larger bag and not placed loosely in packing material where they may be lost during quarantine or customs inspection.
Since seeds may have to undergo fumigation before shipment or on arrival at destination, it is important that they should not be sent in too large quantities in any one container: that would impede penetration of the fumigant as well as airing after fumigation.
Dry-stored seeds should be in the best condition as to moisture content when packed; the package and the air in the package should be dry. Packages should be kept in cool dry rooms while awaiting shipment and during transit. Shipments should be timed to reach the destination just before the time of sowing.
2. Seeds that require moist packing. These include seeds of oak, chestnut, silver maple, magnolia, holly, rose, palm, and many other large seeds. They should be well-mixed with pulverized sphagnum moss, ground peat, coconut fiber or sawdust, that has been moistened and squeezed dry. (A mixture of equal weights of dry packing and water will give adequate moisture content to these materials). Hevea seeds are often shipped in powdered charcoal.
After thorough mixing with the moist packing material the seeds should be placed in water resistant containers. Here again polyethylene plastic has been found the most suitable material since it maintains moisture, while allowing the seeds to breathe, so minimizing the danger of heating. Although this plastic is expensive, it can be re-used several times if carefully handled. Tests have shown that moss packed in this film can be kept moist for a year or more with no addition of water. If this material is not available, waxed paper or other waterproof wrapping should be placed around the package and the whole placed in a stout canvas bag, or in a box that can give outer protection.
Seeds that are prone to germinate when held in moist packing may be treated with an inhibitor such as maleic hydroxide.
It should be emphasized that the quantity of seeds or plant material shipped in one container often has an important influence on the condition in which the material arrives. Even with seeds packed in polythene bags, those with small quantities per bag often endure transport better than larger quantities in one package.
Large seeds like walnuts, hickories and acorns can be shipped satisfactorily in cool weather, if dried slightly on the surface, and then shipped loose in open boxes or cans or in loose sacks.
Coating large seeds to prevent water loss
A method that has been found successful in preserving in moist condition during shipment the seeds of certain, but not all, species requiring this treatment, is to coat each individual seed with paraffin. This is especially useful for seeds that will not tolerate drying, yet tend to germinate if moisture is maintained. The following method has been used at the Arnold Arboretum in the United States of America:
(a) Keep seeds at room temperature a few hours before treating.(b) Heat and maintain parowax to 71-77° C (23-25° F) in an adequately large container.
(c) Place seeds in a screen-type container (such as a wire-basket used for holding test tubes). The seeds should be only one layer deep, and loose enough so they can roll around easily.
(d) Shake the screen vigorously, keeping the seeds in rapid motion while dipping them for a moment in the hot wax. Continue shaking after removal until wax turns white and hardens on the seeds.
(e) Toss the seeds out on a piece of waxed paper. As soon as the wax has hardened the seeds are ready for shipment. Unless the seeds are very cold the whole immersion process should require only a few seconds.
(f) The waxed seeds must be packed in ground cork, dry sphagnum moss, sawdust or other filler, so the wax will not be scraped off during transit.
When the time comes to sow the seeds, the wax must be partially scraped off in order to admit water more freely.
This method was found to be very satisfactory for shipping Quercus alba and Q. montana and less so with Castanea pumila and Aesculus parviflora serotina; but even in the latter two species there was a marked superiority in keeping viability over other methods of shipping.
Various latex preparations have also been used for the prevention of water loss in seeds and other plant parts during shipment. Coatings that crack or peel are unsatisfactory. A strip-coat or dip in ethyl cellulose gives a resilient, easily removed coating.
General instructions
The selection of a packaging medium for a given lot of seed depends upon the quantity to be shipped, the length of time the seeds will be in transit, and the temperatures and moisture conditions to which the shipment will be exposed. The conditions under which the seeds have been stored up to the time of shipment influences the choice of packing method.
Cool dry shipping. If shipment is by airplane, or train or truck in cool weather, moisture-proof wrapping is not required for most seeds if travel time does not exceed two weeks. Paper packets such as strong jute envelopes are suitable for small samples; double cloth bags loosely packed are better for larger quantities.
Maple and oak can be sent in this manner in small quantities only. Large quantities should be divided into small lots for shipment.
Fluctuating temperature or moisture. Under such conditions, the longer the seeds are in transit the greater is the danger of moist seeds drying out, or dry seeds absorbing moisture. Conifer seeds should be dried to optimum moisture content and packed in moisture proof wrapping. Moist-packed seeds should also have moisture-proof wrapping to protect against water loss.
Air shipments of hermetically sealed seed run the risk of exploding at high altitudes, unless the container is extremely strong or the seeds are vacuum-packed. It is best to have the containers as full as possible, so that there is the least possible air in them.
In spite of all precautions it happens frequently that some shipments come through in good condition, while others, packed in the identical manner and sent by the same carrier, become spoiled in transit. Chance still plays a role. Packages may be piled against a steam pipe on shipboard or on railroad or they may be allowed to freeze, while other more protected locations in the freight escape such extremes. Sometimes packages that are delayed or that may lie over for several days in a freight or express office experience extremes of temperature not encountered en route.
Wrapping materials- moisture proof
Metal foil:
heat-sealed aluminum foil; aluminum foil-backed kraft paper; copper foil-backed paper or cloth.
Plastic film:
Polyethylene film; Polythene; Cryovac; Kordite; Koroseal; Pliofilm; Ceran; Vaposeal; Airwrap; Vinylite; Duraclear; Cellophane; Alathone.
Parafined cardboard drums and boxes
Waxed or parafin paper
Plastic jars and bottles
Glass jars, tubes, jugs and carboys
Tins
Waterproof paper lined bags of cotton or burlap
Rubberized fabrics and papers
Wrapping materials: - non-waterproof
Heavy kraft or jute envelopes:
Special seed envelopes with a double-locking fold.
Cotton sheeting bags
With or without rodent-proofing impregnation.
Canvas or burlap sacks
Labelling
All lots of seed whether small or large should bear a secure label on the innermost envelope, bag, box or other wrapping. On small lots the label may be in the package itself as on a folded seed envelope. On large bags or cans a tag or label should be enclosed with the seed itself as well as an outside label.
The seed consignment form, approved by the Sixth Session of the Conference of FAO to facilitate the exchange of forest seeds and plant material for scientific use, provides space for the names and addresses of the consignee and the sender, the gross weight of the package, the nature of the contents, the common and scientific (Latin) names of the species, and record of disinfection. An identification number referring to other data pertaining to the seed should also be placed on all tags, tickets and labels. Certification tags issued by quarantine inspectors and customs officials will also be affixed to each package.
At the invitation of the Argentine Government a meeting of officials technicians and industrialists will take place at Buenos Aires in October to discuss pulp and paper development in Latin America. The meeting, which is being organized under the joint sponsorship of FAO and the Economic Commission for Latin America, will be in the nature of a round-table discussion and seminar.
It is expected that representatives from all the Latin-American republics will attend, as well as prominent specialists in the pulp and paper field from other parts of the world. Emphasis is to be given to the economic and technical phases of manufacturing pulp and paper from locally available resources and to problems affecting markets. Among the items to be discussed will be:
1. pulp and paper consumption, production and trade in Latin America;
2. economic aspects of pulp and paper manufacture:(a) from conifers,
(b) from tropical and sub-tropical broadleaved woods,
(c) from bagasse;3. essential steps in planning new pulp and paper industries;
4. development prospects for pulp and paper industries in selected Latin American countries.
The Eighth Congress of the Pacific Science Association, which embraces all countries in or bordering the Pacific Ocean in Asia, Oceania and the Americas, was held in the Philippines in November 1953. The Proceedings are obtainable from the Executive Secretary, National Research Council of the Philippines, University of the Philippines, Quezon City.
Among the important recommendations adopted on forestry, one recognized the need for coordinated forest products research in the Pacific area. Attention was drawn to the card system developed by the Division of Forest Products, CSIRO, Melbourne, Australia, which with slight modifications is already formulated for Malaya, New Guinea, North Borneo, Australia and the - Philippines. It was suggested that other Pacific countries desirous of adopting such a macroscopic card sorting system should use a similar card to contain information exchangeable within the Pacific region.
Chairman of the Standing Committee on Forest Resources of the Pacific Area was H.G. Keith, Chief, FAO Forestry Mission, Philippines. Members were drawn from Australia, Canada, Hawaii, Honduras, New Zealand, Nicaragua, North Borneo, Peru, the Philippines and the United States.
The Pacific Science Council decided to hold the Ninth Congress at Bangkok in January 1958.
