[2] In charge Field Department, California Almond Growers' Exchange.
In order properly to understand that answer, and I shall attempt to give one later, certain fundamental relations and limitations must first be considered; then the possibilities of any given line of procedure may be more clearly understood.
Botanically the almond is very closely related to the peach, both belonging to the genus Prunus, sub-genus Amygdalus. The species of the peach being persica, and of the almond, communis. In fact the two trees are in many respects so much alike that it is possible to select twigs and leaves from each which cannot be distinguished except by an expert, and even he may be misled at times. Ordinarily, however, they are of sufficient difference to be readily distinguished.
In the fruit the principal difference is that the fleshy portion of the peach becomes in the almond a leathery hull which splits at maturity revealing a seed or nut, the shell of which is generally softer than that of the peach pit. The kernel may or may not be bitter, depending upon the characteristics of that particular seedling. If 100 almonds from a sweet almond tree are planted and brought to bearing it is probable that from a third to a half of them would produce bitter almonds. As a matter of fact, we have had by actual tests as high as 50 per cent. bitter. The peach, on the other hand, will, probably in 99-1/2 per cent. of the cases, produce a seed with a bitter kernel, only very rarely a seed developing which will produce edible kernels. The same is true of the apricot, the Smyrna variety being an edible apricot with an edible kernel.
The almond is normally the first of the stone fruits to begin growth and come into blossom in the spring and is also normally the last tree to become dormant in the fall. It is evident, therefore, that its normal winter resting period is comparatively short. The peach has a much longer resting period than the almond although less than the apple, pear and other similar fruits, and it is for this reason that peach production is possible in a commercial way in many sections of the East.
In California, where almonds and peaches are very often planted in close proximity, many seedlings are known which are very evidently natural crosses between the peach and the almond. In addition many artificial crosses have been made with no difficulty and have been planted and brought to maturity. The products of these crosses have shown the same general characteristics as those found naturally.
We are familiar with a peach-almond growing on the edge of a large almond orchard in California which produces good crops of fruit quite regularly. The fleshy portion or hull is almost edible, being much drier than the flesh of an ordinary peach and yet much more fleshy than the hull of the ordinary almond. It has a slight amount of astringency, a characteristic of the almond hull, but not sufficient to prevent its being eaten. Upon maturity this fleshy portion or pericarp splits but does not open as is usually the case with almond hulls. Inside this the pit, stone, seed or nut, or by whatever name it may be called, exhibits characteristics of both the peach and the almond. It does not have the deep corrugations of the peach pit nor does it have the comparatively smooth shell with small pores of the almond. In this particular variety the kernel is mildly bitter. In almost every respect this cross exhibits characteristics of both the peach and the almond. In other cases this is not true, some approaching more nearly the almond type while others are almost indistinguishable from peaches. In other words, the variations are those naturally to be expected in hybrids.
Now to return to the almond again. We find that for best results in production the almond must be grown in a climate where the winters are comparatively short and yet where there is sufficient cold weather to force the trees into complete dormancy. Where the winters are long or the summers are so dry as to force the trees to come dormant too early in the fall there is a great tendency to premature blossoming in the spring. In other words, the first warm weather in the late winter will bring the trees into bloom because of the fact that they have completed their normal rest period. This same condition has been found to be true of certain varieties of peaches which can be grown in the South but do not do well when planted in the North. It is for this reason primarily, in our judgment, that almonds do not produce under eastern conditions. There are other factors, such as extreme humidity, which may have a bearing, and undoubtedly would in the maturing of these nuts, but this should not prevent them bearing provided they could escape the adverse weather of late winter and early spring.
A mistaken notion has been given considerable credence that the almond is much more tender to frost or cold than the peach. Our experience, where the two have been grown side by side under identical conditions, is that the almond will stand fully as much cold as the peach and in some cases even more. The reason why almond crops are lost oftentimes when peach crops are not is due to their earlier blossoming and consequent subjection to the more severe weather of early spring which the peaches avoid.
It is evident, therefore, that the principal problem in producing almonds in regions of long winters, as compared with those localities where almonds can be produced, is to secure an almond which naturally has a long resting period, resulting in late blossoming, and yet one which will mature its fruit reasonably early. An almond tree beginning to blossom about the first of February will usually ripen its crop between the first and middle of August, though sometimes later. Those beginning to blossom about the first of March or later ripen their crops during September usually and often extend into October.