I5 6 Yearbook^ of Agriculture 1949 



selected for resistance to poplar dis- our new hybrids, selected for disease 

 eases present in the Maine plantations, 

 and they now are being subjected to 

 direct inoculation tests. The variation 



resistance, will be valuable over large 

 areas outside the Northeast, I believe 

 additional breeding is necessary to pro- 



amonVth7ne^ "hybrids in susceptibility duce the best adapted and fastest grow- 

 to damage by Japanese beetles has been ing hybrids possible for the warmer 



regions of the country. Such breeding 

 should include the native southern and 

 western poplars and the best of our 

 disease-resistant hybrids. 



Research with varieties and hybrids 



another" major~point in" selecting^the of poplars is going on now in Canada, 

 hybrids for further testing. All of the Europe, Great Bntam, Scandinavia, 

 selected hybrids grow practically 100 the Soviet Union, South America, 

 percent from cuttings planted directly South Africa, and Australia. The re- 

 in the field on properly prepared search in several countries is on a much 



larger scale than in the United States. 



observed for several years in Connecti- 

 cut, Pennsylvania, and Maryland. Only 

 a few have so far been found suscep- 

 tible to the insect. 



The ability to root from cuttings is 



ground. The branching habit has also 

 been considered ; sometimes it has been 

 possible to select hybrids with few and 

 small-diameter branches. The largest 

 branches on some of these sparsely 

 branched hybrids, trees 60 to 70 feet 

 tall, are less than 3 inches in diameter. 

 Trees with few and small branches will 

 require a minimum of labor for limb- 

 ing-out, and will provide lumber or 

 veneer logs with a minimum of small 

 knots. 



FOR OTHER SECTIONS of the United 

 States, the hybrids are promising. A 

 few of the earliest selections that were 

 tested on a small scale in the Pacific 

 Northwest have been reported to be 

 better than the native cottonwoods in 

 rate of growth and resistance to dis- 

 ease. Evidence on this point is not yet 

 conclusive. 



One should remember that the orig- 

 inal purpose of the poplar-breeding 

 project was to develop fast-growing 

 trees for pulpwood forestation in 

 Maine and New England. The hybrids 

 were planted in western Maine, where 

 the growing season is short and winter 

 temperatures drop far below zero. 

 Hundreds of seedlings failed to survive 

 this rigorous test many because they 

 continued to grow too late into the fall, 

 others because they started to grow too 

 early in the spring. Some of the non- 

 hardy hybrids that were lost in Maine 

 might have done exceptionally well in 

 a warmer climate. Although many of 



Poplars are so important to the forest 

 economy of Europe that before the war 

 their culture and improvement was 

 studied in practically every European 

 country. Since the war, the interest of 

 European foresters in poplars has 

 greatly increased. The International 

 Poplar Commission, established in 

 1947, has sponsored two international 

 conferences on poplar, in Paris in 1947 

 and in Rome in 1948. 



IN THIS COUNTRY, poplars for re- 

 forestation have not come fully into 

 their own because of two handicaps. 

 They are susceptible to diseases that, 

 under certain conditions, can wipe out 

 an entire plantation, and they require 

 considerable care in planting and are 

 highly intolerant of both top and root 

 competition. They cannot be planted 

 and forgotten on abandoned fields or 

 brush land; the ground must be pre- 

 pared properly before planting, and 

 the plantation has to be kept free of 

 grass and weeds for at least the first 

 year. Later the trees must be thinned 

 before mutual competition begins to 

 interfere with their growth. On the 

 credit side, the hybrid poplars respond 

 quickly to good care, and their rapid 

 growth will pay a profit on the labor in- 

 volved. Carefully selected hybrids will 

 largely eliminate the disease hazard. 



The future is bright for fast-growing, 

 disease-resistant poplar hybrids. Pop- 

 lar wood in this country is used for 



