The Almond in California

by R. H. Taylor

ROOTSTOCKS

There is much to learn yet regarding the behavior of the different roots under varying conditions when used as stock for the almond, but sufficient information has already been gathered to permit of certain recommendations being made.

Almond Root.—The greatest proportion of almonds in this state are on almond roots. Where the most desirable soil, moisture and drainage conditions exist it is best to select the almond root. It will live in comparatively dry soils, but cannot be expected to make a tree of large size or bear crops of nuts if the dry conditions continue. Where irrigation is not available, and the soil is deep and of proper texture, sufficient moisture may be retained in most years by cultivation to enable the tree to grow and bear fruit. When extra dry years come, the almond root may not enable the tree to grow or produce any better than would another kind of root, but it will carry the tree over a few dry seasons as well or better than any other. Then, when sufficient moisture does come, the almond root is ready to start the tree off in its normal course with the least loss of time.

Fig. 4.—Languedoc almond on peach[3] root; typical of other trees in same orchard, near Davis. Planted about forty-seven years before. Compare with trees in same orchard on Myrobalan root, as shown in [Fig. 5].

The bitter almond is often recommended as being superior to the sweet almond as a stock. This claim has never been proved. Experiments indicate that there is fully as much variation between the bitter almond seedlings grown from seed from different trees as there is between seedlings from bitter and sweet almonds. Both are equally subject to attack by gophers. The grower’s chief object, therefore, should be to secure as healthy, vigorous trees as possible whether they be on sweet or bitter almond roots.

Peach Root.—Where the soil moisture is quite variable in different portions of the soil, or variable from time to time during the growing season, the peach root will probably be most satisfactory. Soils less than six or eight feet deep, or where gravelly or hardpan layers occur at less depths, are not satisfactory in most cases for the almond root, and under these conditions the peach root is better. The peach root is a little better where irrigation is practiced during the summer, and especially so where there is danger of slow drainage of excess water from the soil. The peach does not thrive with standing water around its roots, but will better withstand fluctuating or temporary extremes in water supply than the almond. Its union with the almond is entirely satisfactory. See [figure 4].

Fig. 5.—Languedoc almond on Myrobalan root, typical of many other trees in same orchard, near Davis, planted about forty-seven years ago. Compare with trees planted same time on peach root as shown in [Fig. 4].

Davidiana Root.—Within the last five or six years the United States Department of Agriculture has introduced the seed of a Chinese peach, Prunus davidiana, the root of which is more resistant to alkali than the ordinary peach. This has been found to unite readily with the almond, although experiments have not yet gone far enough to fully determine its true value. It gives promise, however, of being a very desirable stock for sections where alkali may be troublesome.

Undesirable Roots.—The Myrobalan plum has frequently been recommended as a stock for the almond on poorly drained soils. The two make a strong union, but the plum root grows much slower than the almond top, as indicated in [figure 5]. A comparison with [figure 4], in which both trees are 48-year-old Languedoc, shows that the trees on Myrobalan root are pinched-in below the union while those on peach root are swollen at the base. Even young trees show the same pinching-in below the union. Almond trees on Myrobalan root do not make as large trees nor do they bear satisfactory crops in any portion of the state where it has been possible to compare them with the same varieties on other roots in similar situations.

The apricot is occasionally recommended because of its strong, thrifty growth, but it is a mistake to attempt to use it, as the union is not satisfactory. The trees grow thriftily for awhile, but before they reach full bearing they either break off at the union or are blown over above the union by moderate winds.