What Do We Plant?

Above: A onetime Navy plane is used to seed white pine on burned-over forest lands in Maine.

FIRST THE SEED, THEN THE TREE

PAUL O. RUDOLF.

IN THE United States more than 600 species of woody plants are useful for conservation planting, and some 75 million acres are in need of reforestation. For that, more than 100,000 tons of forest seeds will be needed. We should therefore know all we can about forest seeds where they are borne, how often good crops come, when seeds are ripe, when is the best time to collect, how to clean them, how to store them, how to obtain prompt germination, how good they are, and what their origins are.

SEEDS DEVELOP from flowers. The floral organs are the stamens and the pistils, which produce the sperm, or male cells, and the egg, or female cells, which, when united, produce the seed. Some trees and shrubs have bisexual, or perfect flowers. Many, however, have stamens and pistils borne in separate flowers, either on the same plant or on separate plants. Others have both perfect and unisexual flowers on the same plant. A knowledge of these habits helps the seed collector to know what trees are likely to produce seeds and also what crop to expect from the abundance of blossoms.

A typical tree seed consists of an embryo, usually embedded within an endosperm. ( sometimes very thin or even absent) , all enclosed in one or two seed coats. The embryo is a complete plant in miniature. The endosperm contains food reserves that become available for germination and early growth. The seed coat protects the embryo from injury before germination.

Tree seeds range in size from the powderlike rhododendron seeds to the large black walnuts. They differ greatly also in shape, color, and other characteristics. From the standpoint of collection and extraction, however, seeds fall into three groups:

1. True seeds readily extracted from dry fruits. Included in this group are trees whose seeds are borne in cones (fir, hemlock, larch, pine) or in fruits that split open, such as pods (honey-locust, locust, yellowwood), or in capsules (e. g., the fremontia, poplar, willow). Commercial seed is almost always the true seed.

2. Dry fruits with seeds surrounded by a tightly adhering fruit wall. Included are species whose seeds are borne in achenes ( clematis, cliffrose, eriogonum) , the nuts ( chestnut, filbert, oak), and samaras, or key fruits ( ash, elm, maple). Because it is hard to do so, seeds of this group are seldom extracted from the fruits. For all practical purposes the entire fruit is the seed.

3. Seeds of fleshy fruits. Included are species whose seeds are borne in accessory fruits (buffaloberry, wintergreen) , aggregate fruits (raspberry), the berries (barberry, currant, honeysuckle) , the drupes ( cherry, dogwood, plum, walnut), multiple, or collective fruits ( mulberry, Osage-orange) , or ponies ( apple, pear).

To SUPPLY the needs of the seed trade and reforestation, large quantities of tree seeds must be collected, extracted, and stored every year.

In scouting out supplies, the seed collector should keep eight points in mind :

1. The parent plants should be of desirable form and development.

2. Trees whose crowns receive light from above and the sides usually produce the bulk of the seed crop.

3. The flowering habit determines which trees will produce seeds and the part of the crown in which they are borne.

4. Estimates based on actual count of fruits on representative trees or on small sample plots well distributed over the collecting area are most reliable.

5. "Tree seed farms," set aside in mature stands of particularly good development or plantations of known good seed source, which produce seed in reasonable abundance, will provide desirable local collecting areas.

6. The tree seed-crop reporting services, available in some regions, tell the collector where good local crops are.

7. The soundness of seeds in individual localities, or even on individual plants, should be tested.

8. Next year's potential crop can be estimated from the number of first-year fruits for such trees as the pines, black oaks, and others which require 2 years to mature their fruits.

RIPENESS of the seed and the length of time it may remain on the plant or on the ground without deterioration or injury determine the time of collection. Collectors usually judge the ripeness of fruits by their general appearance, color, degree of "milkiness" of the seed, hardness of the seed coat, their attractiveness to animals, or some combination of these factors. For some pines, ripeness can be determined more accurately by the floatability of freshly picked cones in motor oil, kerosene, or other liquids.

The exact time for starting seed gathering must be determined for each species in each locality each year. However, the general season in which to make collections is known for a great many species, some of which are:

Spring: Berlandier ash, river birch, cottonwoods, elms (except Chinese), red maple and silver maple, poplars, and the willows.

Summer: Bigcone-spruce, cherries, Douglas-fir, elders, alpine larch, magnolias, red maple, mulberries, Siberian pea-shrub, plums, serviceberries, California sycamore.

Fall : The ashes ( except Berlandier) , beeches, bigcone-spruce, birches (except river birch), boxelder, catalpas, cherries, Douglas-fir, Chinese elm, firs, hickories, junipers, the larches (except alpine), magnolias, maples (except the red and silver), oleasters, Osage-orange, pecan, most pines, plums, spruces, sycamores, walnuts.

Winter: Ashes (except Berlandier), yellow birch, the boxelders, catalpas, Osage-orange, black spruce, Norway spruce, sycamores, walnuts.

Any season : Aleppo pipe, bishop pine, jack pine, lodgepole pine, Monterey pine, pond pine, sand pine.

Forest seeds commonly are collected from standing trees. Most tall trees must be climbed and the fruits or seeds detached by hand picking, by cutting them off, or by knocking them off. In hand picking, the fruits usually are placed in containers. If the fruits are cut or knocked off, they are usually caught in sheets spread below. Seeds usually are hand-picked or flailed from small trees or shrubs without climbing them.

It is usually cheaper to collect seeds from felled rather than from standing trees. The collector must, however, gather seeds only from trees cut after the fruits have begun to ripen.

Twenty or thirty years ago conifer cones frequently were gathered from squirrel hoards in the Lake States and the West. This is still done to some extent. However, seed collection from rodent caches is of limited usefulness because the parent trees are unknown, hoards are difficult to find consistently, and few species are included. Some successful collectors gather squirrel-cut cones from the ground.

Seeds or fruits are gathered from water surfaces or from drifts along the shores for a few tree species, such as baldcypress and some of the willows.

Fruits should be taken to the extraction point soon after collection. Fleshy fruits should neither be crushed nor dried for very long. Others should be spread out and dried partially before shipment.

To PREVENT spoilage, to conserve space and weight in the shipment and storage, and to facilitate handling and sowing, seeds of many species must be separated from the fruits and cleaned of fruit parts and debris.

Seeds are separated from the fruits by drying, threshing, depulping, or cleaning procedures such as fanning and sieving.

The simplest method of drying is to spread the fruits in shallow layers so that there is free circulation of air across and around each fruit. Where the climate is damp, or the quantities of fruit great, drying is usually done under a roof.

Artificial heat is necessary to open some cones readily. Artificial drying ordinarily is done in special kilns which aim to provide the highest dry heat that the seeds can stand without injury. Two general types of kilns are used for extracting seeds from cones : The simple convection and the forced-air. The former has long been in use; the latter has been developed since 1934. Newly developed in Canada is a kiln using batteries of infrared lamps.