As far as possible, districts should be chosen where a definite cold winter season exists. Warm weather and lack of freezing temperatures do not hold the trees fully dormant and any frequent occurrence or unusual continuation of spring weather in the winter will start the trees into growth; cooler weather following, interferes with the normal flow of sap, results in injury to the tree and blossoms, and often causes gumming of the nuts which mature. This condition exists largely in the lower elevations in Southern California and especially in the coastal portion, where the ameliorating influence of the Pacific is felt. This same condition exists close to the coast in the northern portion of the state. Further inland and at higher elevations the winters are more pronounced, and where these are not too severe or prolonged the almond thrives best. SACRAMENTO VALLEY AND FOOTHILL SECTIONS Commencing in Solano County, about eight miles northwest of Suisun and extending as far north as the southern end of Shasta County, close to the base of the foothills on the west side of the Sacramento River, are a large number of orchards on the bottom lands of the valley. These are found principally on the higher lands along the banks of streams flowing from the Coast Range in a generally easterly direction to the Sacramento River. The two most important streams of this type are Putah Creek, forming the boundary between Yolo and Solano counties, and Cache Creek, flowing through the Capay Valley and across Yolo County to the Sacramento River. These plantings being on the floor of the valley are more subject to frost than the foothill plantings, but they have the advantage of being on the rich valley soils, and while they may lose a crop occasionally from frosts, they make it up in the long run by the much larger growth of the trees and their ability to produce larger yields. Many orchards do not show any such ability to produce large crops, but such a failure must be attributed to lack of pruning and care, rather than to any inherent inability of the large trees to produce nuts. Again, trees on the rich and moist bottom lands may be kept so vigorous and healthy by good care that they are apparently able to endure lower temperatures than less vigorous trees on the shallow and poor upland soils where frosts are less common or severe.