WALNUT, a tree of the genus Juglans and of the family Inglandacece. The species, of which about 10 have been described, are na tives of the northern hemisphere, beihg con fined to the temperate parts. In America they are found as far south as Mexico. They are characterized by rough bark, compound leaves aromatically fragrant when bruised, staminate flowers in catkins, pistillate flowers in few to .
many-flowered racemes and followed by large drupes with inedible husks and hard nuts, the kernels of which are valued in some species for food, dessert or the oil they yield upon expression. A majority of the species are pnized for park planting because of their hardiness and the graceful form they acquire when well established. For this purpose the most esteemed in America is probably the black walnut (Juglams nigra), which has a range trom the New England States to Minnesota and southward to the Gulf States. It is a graceful and • imposing tree which often reaches 150 feet in height, has usually an erect trunk and a broad airy round top. It is also valued to some extent for its rough hard shelled nuts which are often seen in the mar kets. Its wood is one of the most highly prized native woods, being used extensively for furni ture malcing, interior finish of houses where anatural woods') are used, its deep brown tint tnaking rich contrasting effects with other woods. Several other species also furnish nuts found in various markets where the trees are native and the husks of several are used for dyeing and tanning. The species most esteemed for its nuts is, however, the Persian or ((Eng lish* walnut (Juglans regia), which is indige nous from China to southeastern Europe. It has been cultivated for centuries in the Med iterrantan region, whence it has been taken to mild climates throughout the world. The tree is only about half as large as the preceding species but is much the same in appearance.
nuts have smoother, softer shells and usually finer-flavored kernels. This nut is one of the most important in the world. Only during the closing half of the 19th century, how ever, has it been grown commercially in the United States and here only in California. The crop marketed in 1915 from this State was officially estimated at about 14,300 tons, worth approximately $4,250,000. Besides these home supplies large quantities are imported from the Mediterranean region but these importa tions will probably dwindle into insignificance when Californian orchards come into full bearing.
Since the trees seem to be exacting in their demands, the areas in which they can be culti vated are somewhat restricted. They are con
sidered susceptiblt to frosts after their growth has started though fairly hardy while dormant; they seem to be unable to stand hot weather since the nuts are more or less injured; they seem to fail upon lands in which standing water is nearer the suriace than 20 feet, also in soils with hard clay subsoil and in poorly drained soils. They are thus almost restricted at present to the deep alluvial soils of the four southern counties of California, but by planting varieties which vegetate late in the spring and by avoiding the conditions mentioned it is be lieved that the region of successful cultivation may be extended even to northern counties. The seeds are planted about 12 inches asunder in nursery rows four feet apart, cleanly culti vated, irrigated during midsummer and hardened off by withholding the water in autumn. They will usually be under two feet in height when one year old when they are root-grafted to de sirable varieties. The grafts will often grow eight feet during the first year. Either when oire year or two years old the plants are set in permanent quarters about 50 feet apart. Little pruning is needed except to correct bad form, the branches being started about four feet frorn the ground. The orchards are kept cleanly cultivated throughout the season, the first plowing in spring being at least six inches deep. Irrigation is also given if needed; al ways during the winter. The trees of even the most precocious varieties rarely produce profitable crops before six years old and 10 years is nearer the average age. Trees reach full bearing when about 20 years old and continue for 30 years or more. Some trees in Europe are said to be more than 100 years old. VVhen the nuts begin to fall they are shaken down, gathered by women and children usually and spread on trays for a week to dry. The nuts are then graded into sizes by passing them over sieves after which they are dipped in a bath of sal soda, chloride of lime and sulphuric acid to bleach the brown shells and give them the ecru tint demanded by the market. After dipping they are rinsed in clear water. Formerly sul phur was used for this purpose but it was found to itnpair the quality of the nuts and has been abandoned. After drying the nuts are again graded into light and dark. The latter with die broken ones are used by confectioners; the former are shipped to market in sacics holding about 110 pounds. Consult United States Department of Agriculture, Division of Pomology, 'Nut Culture in the United States' ; University of California Bulletin No. 231.