While the walnut is the hardiest of trees and in many cases has borne
heavily in Oregon without cultivation, experience has proved that, like
fruit trees, cultivation up to the tenth or twelfth years increases the
growth, the yield and the quality of the product. After full maturity no
further cultivation is necessary, the tree taking care of itself with
the independence of any forest tree.
With a young grove it is best to plow between the rows after the rains
cease in the spring, and then stir the ground occasionally all through
the summer with the harrow or disk; this holds the moisture. When some
trees seem backward a trench should be dug some two feet or so away, and
a couple of feet deep, filled with fertilizer and closed over. This will
encourage hardier and more rapid growth. Lime can also be used with good
effect, it being customary in England to haul wagon loads to the walnut
lands. Continually hoeing and digging constitute the best treatment, as
one tree on the Prince place, a Mayette, has proved. It was given daily
cultivation, by way of experiment, and more than doubled the size and
yield of other trees of the same age not so treated.