AMATEUR TREE BREEDERS? WHY NOT?

ERNST J. SCHREINER.

The amateur can find ample scope for a creative interest in breeding and hybridizing trees. There are only two absolute requisites, a keen and lasting interest and sufficient available land for growing trees. Plant breeding was practiced as an art long before the discovery of the principles upon which scientific breeding rests. A scientific background is not necessary to the art of tree breeding; the techniques are relatively simple and inexpensive.

Better shade trees and better forest trees are needed. In many tree species the same controlled pollinations may produce both, but the amateur tree breeder will be wise to direct his major efforts into one or the other of these two fields. In my opinion, the breeding of shade and ornamental trees offers several important advantages. Just one example: The breeding enthusiast with only a little ground available for growing trees cannot work with forest types, but he can breed, grow, and select ornamental dwarf types.

Tree-breeding methods are much the same as those used by the breeder of the agricultural and horticultural plants. Controlled breeding requires protection of the female flowers from chance pollination both before and after the desired pollination has been made. That usually is accomplished by covering the unopened flower buds with bags of paper, vegetable parchment, light canvas, or cloth. Bags made from cellulose sausage casings, which are available in a fair range of sizes, are excellent for many kinds of trees.

For trees that produce separate male and female flowers on the same twigs ( for example, birch, hickory, oak), one must remove the male flowers from the part of the branch that is to be bagged. If the tree bears perfect flowers (male and female parts in the same flower), the stamens, which produce the pollen, must be carefully removed before they mature. Such emasculation is not necessary if the tree does not set viable seed to its own pollen. This latter point can be determined by bagging flowers that have not been emasculated.

Bags of glassine or heavy brown paper are cheap, are available almost everywhere, and are generally satisfactory for bagging many kinds of trees. The size of the bags depends upon the tree species being worked; they should be large enough to allow for the growth of shoots and leaves. A glassine bag of suitable size is tied securely over a bit of cotton batting wrapped around the stem. The cotton prevents the entrance of pollen and keeps the bag from slipping back and forth. A slightly larger brown-paper bag is then tied over the glassine bag for mechanical protection.

Transparent bags are advantageous because flower developments can be observed more easily. Strong, transparent bags are easily made from commercial sausage casings, which come in cylindrical strips of various diameters and lengths. Strips cut into suitable lengths can be made into pollination bags in several ways; one easy way is to gather and tie one end of the casing over a small cotton plug.

When the female flowers under the bags are fully open and receptive, they must be dusted with pollen from the selected male parent. For some insect-pollinated species it is safe to remove the bags and to apply the pollen directly with a small cotton swab, but the wind-pollinated trees ( such as the oaks, hickories, and poplars) should be pollinated without removing the bags. With such species a tiny puncture is made in the glassine bag and the pollen is blown into the bag with an ordinary glass medicine dropper. The small puncture in the bag is then immediately covered with scotch tape, or a second glassine bag may be tied over the original. The heavy paper bag is then replaced and the bags are left in position until the flowers are past bloom. Sausage-casing bags may be punctured for pollination, or the tip of the bag may be opened carefully, just enough to admit the dropper. The medicine droppers work best if the ends are drawn out to a relatively fine point in the heat of a gas flame. A loose wad of absorbent cotton inserted in the dropper, just below the rubber bulb, will conserve pollen by keeping it out of the bulb. Such droppers are cheap enough to be used for one kind of pollen and then discarded.

Pollen can be collected directly from the tree selected as the male parent, but there is less danger of contamination if flowering branches are cut and kept indoors, in water, until the pollen is shed. Special care must be taken to prevent any mixing of pollen from different trees. Pollen can be handled most conveniently in small vials stoppered with plugs of absorbent cotton. Most pollen will remain viable for at least several days, if the cotton-stoppered vials are kept in a tight jar and stored in a refrigerator.

Accurate records are essential; flowers, pollen, seeds, and seedlings should be labeled to provide a detailed record of the parentage of all progenies produced by controlled breeding. The amateur breeder should record such information as location and description Of parent trees, dates of bagging, pollen collection, pollination, removal of bags, collection of seed, storage of seed, and date of planting. Such records are necessary for planning future breeding work, especially breeding directed toward the improvement of particular characters or qualities.

The tree breeder also should collect seed, matured to natural pollination, from both parents of his successful crosses. The seedlings and trees grown from such open-pollinated seed can be used as a "yardstick" to determine how much the control-bred seedlings differ from their parental types.

Seed can be planted in pots, in flats, or in carefully prepared seedbeds; the essential thing is to maintain the identity of each seed lot from the time the seed is collected until the seedlings are planted in a permanent location. The final planting location of the seedling progenies is best recorded on a map.

The study of his progeny trees can keep the amateur breeder occupied for many years. From frequent observations during every month of the growing season, by literally living with his trees, the amateur will soon recognize differences between trees of even the same parentage. Where "yardstick trees" of the parent types are included in the plantation, they will provide a good measure for estimating improvement in the progenies derived from controlled breeding.

ERNST J. SCHREINER has done research in tree breeding since 1924, when he left the New York State College of Forestry at Syracuse University shortly before graduation to work on poplars. His first work with hybrid poplars was as research forester with the Oxford Paper Company from 1924 to 1935. After a year with the Tennessee Valley Authority as associate tree-crop specialist, he joined the staff of the Northeastern Forest Experiment Station as forest geneticist. He holds degrees from the New York State College of Forestry at Syracuse (1926) and from Columbia University.

Many a tree is found in the wood;

And every tree for its use is good:

Some for the strength of the gnarled root,

Some for the sweetness of flowering fruit;

Some for a shelter against the storm,

And some to keep the hearthstone warm;

Some for the roof, and some for the beam. . .

HENRY VAN DYKE