L. D. BATCHELOR, UNIVERSITY OF CALIFORNIA, CITRUS EXPERIMENT
STATION, RIVERSIDE, CALIFORNIA.

The walnut industry of California is just entering a transition period from the planting of seedling groves to the established plantings of grafted trees.  Just as other seedling fruit trees, such as the orange, apple, peach, almond, etc., have been eliminated, so too, the seedling walnut groves of California seem doomed to be replaced by clonal varieties.  In many ways this industry is as much in its infancy as the apple industry of New York was sixty-five years ago, when varieties first began to be propagated in a commercial way by grafting and budding.  This readjustment in the walnut industry is well started, and, although it is likely to be gradual in its evolution, and wisely so, the change seems nevertheless certain.  There are but a very few seedling trees for sale at the present time by the progressive nurseries, and, in fact, only a very few such trees have been set out in groves during the past four or five years.  The demand for grafted trees has been brought about largely by the wide range of variation in walnut seedlings as regards their productivity, commercial value of the nuts, season of harvest and ability of the trees to resist the walnut blight.

In view of the very recent propagation of the walnut by grafting, which has extended over only about ten to twelve years, it is reasonable to expect that the majority of the varieties thus propagated so early in the development of the industry are only partially suited to the needs of the walnut grower.  The nuts from many of these grafted varieties fall considerably short of the commercial standard for high-grade walnuts.  Some of the heaviest-bearing sorts, such as the Chase, Prolific and El Monte, produce nuts that cannot be sold in the very best grade of the commercial product.  On the other hand, the Placentia, which produces one of the most nearly ideal commercial nuts, is not a heavy-producing variety, especially in the northern walnut sections, and is quite as susceptible to walnut blight as the average seedling tree.  Again, the Eureka variety, which seems to successfully avoid the walnut blight during many seasons by its lateness in coming into bloom, is a very moderately yielding variety in the southern sections.  The above examples are only a few of many that might be cited to show the short-comings of most of the varieties of walnuts now being propagated.

The wide range of climatic and soil conditions makes the eventual propagation of quite a large number of varieties inevitable.  While the coast regions are bathed in fog nearly every morning during the growing season, the inland valleys experience an extremely dry climate with high maximum temperatures.  Walnuts are being grown at the present time on soil types varying from the extremes of sand to heavy clay loams.  Many of the future varieties must be especially adapted to some one of these particular environments if they are to stand the test of time.