io THE COMPLETE GARDEN 



as the period between the date in the spring when the normal mean 

 daily temperature rises to 43 degrees Fahr., or above, and the date in 

 the autumn when it falls to below that figure. (The reader should con- 

 sult Bulletin No. io of the U. S. Department of Agriculture, Division of 

 Biological Survey, entitled "Life Zones and Crop Zones." Part III 

 of that Bulletin is especially interesting). These life-zones are, as 

 noted above, adapted to plants requiring growing seasons of similar 

 length and temperature range. Thus, if soil conditions, exposure, and 

 amount of annual rainfall are alike in two distant portions of a zone 

 plants which succeed in one portion may be expected to succeed in the 

 other portion. They may in any event be tried out with considerable 

 confidence when all the conditions are known to be the same, as 

 described above. 



It now seems evident, from recently gathered data, that these 

 zones correspond very closely to belts of country which have similar 

 planting seasons for dormant woody plants, at least throughout the 

 humid regions east of the looth parallel of latitude. By consulting the 

 accompanying Plate II, which has been adapted from the one in 

 the above-mentioned Bulletin, and also the chart (Plate III), which 

 shows the reported length of planting seasons, it will be seen that the 

 stations reporting fall into groups which lie in respective life-zones as 

 shown on the map. 



Thus stations 2, 3,4, and 6, all of which lie in the so-called Transi- 

 tion Zone, including most of New England, New York State, Penn- 

 sylvania, northeastern Ohio, the Alleghanies from Pennsylvania to 

 Georgia, southeastern Ontario, Michigan, Wisconsin, southern Minne- 

 sota, North Dakota, and northern South Dakota, all report a short 

 fall and spring planting season, divided by a long winter season, 

 during which ordinary planting work is impracticable. Stations 

 7, 8, and io lie in the northern limits of the upper Austral Zone where 

 they are influenced by the Great Lakes. Stations 13, 14, 15, and 18 lie 

 outside of the Great Lakes influence in the same zone, which includes a 

 great territory stretching from the Coastal Plain westward to the 

 Great Plains, and from the Transition Zone on the north to central 

 Georgia and northern Texas on the south, except for an arm of the 

 Lower Austral which extends northward along the Mississippi River to 

 Cairo, 111. The first three stations, 7, 8, and io, show the influence of 

 the Great Lakes in that their spring planting season is delayed, while 

 stations 13, 14, and 15 show a markedly later date for stopping trans- 



