GROWING SEASON TEMPERATURES 



247 



Table 10. — Relation of Summer Temperatures to Yield and Character of 



Wine-- 



vines flourish the grapes never become thoroughly ripe and good wine cannot be 

 made where the constant temperature is not at least 68°F. Besides a warm 

 summer, a mild autumn free from continued low temperature is necessary. 

 Some regions are assured of sufficient heat in every summer; others must have 

 a summer warmer than the average to produce a satisfactory wine. Along 

 the doubtful zone of grape growing the careful selection of site is emphasized. 



Variation in Season of Maturity with Amount of Summer Heat. — 



The effect of summer temperatures on the time of ripening and on keeping 

 quahties is well known. Thq Wealthy, a fall or early winter apple in 

 Minnesota, becomes a summer apple in Missouri. The Baldwin loses 

 quality and becomes progressively a poorer keeper toward the south 

 except at higher and cooler altitudes. Sometimes the transition is rather 

 abrupt. The Dudley, a winter apple in Aroostook County, Maine, is a 

 fall apple at Bangor and a summer apple farther south. ^^ Apples grown 

 in southern latitudes develop color over a larger part of the surface, but 

 the colors are more intense in the north. 



SOIL TEMPERATURES 



That the temperature of the soil is not without influence on plant 

 growth is evident from the florist's resort to bottom heat for certain 

 plants and the rather definite heat requirements for the rooting of cut- 

 ings. It has been shown that Opuntia versicolor can be stimulated to con- 

 siderable vegetative growth despite unfavorably cool atmosphere by the 

 maintenance in the soil of favorable temperatures for root growth.^" 

 Lindley^''* statedthatacertain variety of A^^e^ww^ntw though in full vegeta- 

 tive vigor was without flowers when the soil temperature was 85°F., but 

 blossomed at 70 to 75°F., while another variety ceased blossoming at 

 this same temperature. 



Obvious difficulties are encountered in attempting a determination 

 of suitable temperatures for root growth in trees. Lindley^"^ arranged 

 a statement of favorable soil temperatures for various fruits, based on 



