i 5 8 



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 parch- 

 ment, 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 emascula- 

 tion 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 satis- 

 factory 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, trans- 

 parent bags are easily made from com- 

 mercial 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 di- 

 rectly 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 im- 

 mediately covered with scotch tape, or 



