INTRODUCTION

The almond (Prunus communis) is supposed to be native to the countries around the Mediterranean and at present the bulk of the world’s supply is produced in that region. It resembles the peach somewhat in manner of growth and character of blossoms and leaves, but the wood is much harder and the tree is longer-lived under equally favorable conditions. The fruit, instead of having a thick, fleshy pericarp as in the case of the peach, has a thin, leathery pericarp or hull, which splits on ripening and generally opens when dry, exposing the nut inside.

California produces over 98 per cent of the entire American crop and has done so for many years. During the period from 1900 to 1913 the number of bearing trees remained approximately the same, new plantings having replaced old orchards that were being pulled out. The variation in California production from year to year prior to 1915, as shown infigure 1, is due to seasonal variations rather than to change in acreage.

Imports into the United States from the Mediterranean countries are also shown infigure 1, the top line representing the total imports, the other lines, as indicated, showing the proportion of that total originating in the three principal countries exporting to the United States. Previous to 1912 the records of shelled and unshelled almonds were not kept separate. Since the records have been segregated, the percentages of shelled almonds imported each year have been approximately as follows:

With the 1915 crop the production in California entered upon what appears to be a long prospective increase. The large acreage of almonds set out in the last four or five years is the result of greatly improved market conditions due to the successful work of the CaliforniaAlmond Growers’ Exchange. The first of these new plantings are now coming into bearing, and each year for many years in the future will continue to see increased yields. Large acreages are still being planted so that the almond production in California bids fair to continue to grow.

Within the next few years California growers will, in all probability, be forced to accept lower prices for their almonds than they are now receiving. The American markets are fully supplied at present prices, yet constantly increasing acreage will inevitably result in a greatly increased tonnage. European almonds are being produced at a lower net cost and can be laid down on the Atlantic Coast more cheaply than is possible with the California product. This brings the grower face to face with the necessity of becoming more thoroughly familiar with the most economical methods of production and marketing if they are to continue to make a profit. It is essential, therefore, that a careful study be made of all the factors concerned in the growth, production and final disposition of the almond crop.

The almond is the first of the deciduous fruit trees to start growth and come into bloom in the spring, and normally the last one to shed its leaves in the fall. In other words, it has a very short period of rest. When the trees are forced into premature dormancy by mites or lack of moisture, they soon reach the end of their normal rest period before the winter season is over. Then the first warm weather in spring will bring the trees into blossom. In some cases where moisture and temperature conditions are favorable late in the fall, they may actually blossom before the winter season. In young trees that have become dormant unusually early, the rest period may terminate and then the tips of the branches resume growth and continue to slowly develop new leaves at the terminals throughout the winter. Trees which have been kept growing thriftily until the leaves have been forced to fall by the cold weather and frosts of winter, do not tend to blossom as early in the spring, nor do they open under the influence of a few days of warm weather in late winter or early spring.

Young trees blossom somewhat later than the older trees, and buds on sucker growth blossom later than the more mature portions of the same tree. The difference may amount to three or four days or almost a week. Well-grown trees carry large numbers of blossoms over the entire tree, as shown infigure 2.

Fig. 1.—Imports of Almonds into the U.S.Crops of 1899 to 1917.

Fig. 1.—Imports of Almonds into the U.S.

Crops of 1899 to 1917.

The wood of the almond is very hard and strong, enabling the tree to bear the weight of heavy crops where pruning has been given proper attention during the formative period of the young tree. As with other fruit trees, the almond is subject to heart-rot and care should always be exercised to prevent the checking and cracking of large wounds and consequent infection with decay organisms. The hardness of the wood makes it the finest kind of fuel, and when old orchards are being dug up the returns from the sale of wood often more than pay for the expense of digging and cutting up the trees and burning the brush.

The nuts are of two general classes—sweet and bitter almonds. The former is primarily the almond of commerce, though the latter is used largely in the manufacture of almond oil and almond flavoring, as well as in the manufacture of prussic acid. The bitter almond is also used largely in nurseries as a rootstock upon which to bud the almond and some other fruits.

For a long time there has been considerable evidence to show that some varieties are always self-sterile while a few are sometimes self-fertile. Work done in 1916 and 1917 by Tufts[1]shows that practically all varieties are self-sterile and that some of the self-sterile varieties are also inter-sterile. In these tests the principal commercial varieties were used. Blossoms of each variety were pollenized with pollen from its own blossoms and from each of the others. Checks were for natural pollination with each variety. The important results of this work are briefly summarized as follows:

The Nonpareil and I.X.L. are inter-sterile, although both are inter-fertile with the Ne Plus Ultra.

The Languedoc and Texas are inter-sterile.

The I.X.L. and Peerless are practically inter-sterile.

The California has proved the best pollenizer thus far tested, for all varieties that bloom near it.

The Drake is inter-fertile with the Nonpareil, I.X.L., Ne Plus Ultra, Peerless and Jordan, the only ones tested.

The I.X.L. is inter-fertile with the Drake, Jordan, California, Languedoc, Ne Plus Ultra and Texas.

The Ne Plus Ultra is inter-fertile with the California, Drake, I.X.L., Languedoc and Nonpareil.

While the almond is in many ways an easy tree to grow where conditions are favorable, it is more particular in its requirements than most common orchard fruits, and the grower may find it difficult to produce a good, thrifty tree unless he chooses the proper location. Very often it will grow well and make a fine healthy tree, but owing to unfavorable conditions, will not bear regularly, if it all.

Fig. 2.—Seven-year-old Ne Plus Ultra almond in full bloom, at the University Farm, March, 1915, showing distribution of blossoms well down into center of tree. Paper bags cover blossoms pollenized by hand.

Heat.—Where the conditions of soil and moisture are favorable the almond will endure the intense heat of the interior valleys and even of the Imperial Valley, provided it is pruned properly to shade the main branches so as to prevent sunburn. Where trees, by severe pruning, are opened up suddenly to the intense heat of the summer sun, almonds will sunburn, but if the necessary opening up is done gradually, the bark will become inured to the new conditions without danger. The nuts grow and ripen more satisfactorily in the greater heat of the interior than along the coast.

Frost.—The almond tree is hardy and will endure fully as much cold as the hardiest peach without injury. Trees are found growing well in Illinois, Ohio, New York and other Eastern states. In very favorable seasons they may even bear fruit, though this happens very seldom, due to the extremely early habit of blooming before the spring frosts are over. The first warm weather seems to start the trees into bloom, especially where the enforced dormant season of winter is very long.

The blossoms, on the other hand, are very tender. There is a great range in the degree of frost which will cause injury, depending largely on the condition of the tree during the time that the fruit buds are forming and developing, as well as on the duration and severity of the frost. Buds and blossoms on trees which have been forced into premature dormancy, either by lack of moisture or by severe attacks of red spider, are much more susceptible to frost than those on trees which have continued growth late enough in the fall to provide for the proper development and maturity of the buds. After differentiation of fruit buds commences in the summer, the almond leaves should remain on the tree until late into the fall in order to strengthen and develop the fruit buds and store up the elaborated food material for the use of the buds in their normal development through the winter. Studies of almond buds gathered from healthy trees which held their leaves until late fall frosts at Davis, showed the first evidence of differentiation between fruit and flower buds commencing about August 18, while the flower was not completely developed until February 18 following. During the intervening time development proceeded unchecked through the winter even though the tree was apparently dormant. During the time the crop is ripening on thetrees, little is done toward storing food material for the buds. If the leaves turn yellow or drop soon after harvest, the trees do not have the opportunity of storing a sufficient supply of plant food for their normal requirements and the buds are insufficiently nourished during the winter period. The resulting buds are weakened and the indications are that they are unable to endure unfavorable climatic conditions in the spring, such as light frosts, continued cold weather or sudden changes from warm to cold weather.

The most tender stage in the blossoming and development of the young fruit seems to be immediately following the dropping of the calyx lobes from the young fruit as it first commences to swell rapidly. The blossom becomes more and more tender as it opens out and reaches the above stage. After the young fruit has attained the size of a pea it rapidly becomes more resistant to low temperatures. Blossoms with the petals exposed but not yet opened have been known to stand temperatures of 24 degrees F. and blossoms with petals beginning to fall have stood 28 degrees F. No records are available as to the duration of these temperatures. In other cases, blossoms with the petals falling have been killed by temperatures of 30 and 31 degrees F. It must be remembered in this connection that the almond blooms earlier than other orchard fruits and, therefore, is often subjected to much more severe frosts than occur during the blooming period of the later fruits. The greatest injury is likely to occur when a frost follows one or more days of warm weather. When the mean temperature both day and night remains low, frosts that might otherwise kill the flowers or setting fruit do no harm. This is what occurred in February, 1917, at the University Farm, when repeated frosts at blooming time did no harm whatever.

In determining the desirability of a location in regard to its freedom from frost, the possibility of adequate air drainage is an important item. For this reason the lands along the lower foothills immediately above the floor of the valleys are ordinarily much less subject to frost—because the cold air is free to drain away to the lower levels. Generally the lands along the banks of streams which have been built up higher than the other lands of the Great Valleys through which they flow, are less subject to frost by reason of the natural flow of the cold air from them to the lower lands adjacent. For the same reason the planting of almonds in the lower lands of the valleys, no matter how large the valleys may be, should be avoided, unless the locality has been thoroughly tested for a long period of years and has proved to be an exception to the rule because of some peculiar situation with favoring air currents or air drainage, such asmight exist near a natural draw in the hills where the settling of the cold air in some portions of the adjacent valley might be prevented. Such locations are generally confined to very small areas. Oftentimes an opening or draw in the hills may serve as an outlet for the drainage of much colder air from considerably higher elevations beyond, and then the danger from frost is very greatly increased. This is very common where cañons act as drains to conduct the cold air from the high Sierras to the valleys below.

Variable weather conditions, and especially as regards temperature in the spring after growth commences, are highly undesirable. Warm weather immediately followed by cold tends to produce sour-sap, fruit drop and kindred physiological ills. Oftentimes crops have been lost where no frosts occurred after blooming commenced, simply due to sudden changes in the weather. However, it is highly probable that the greater portion of the trouble with fruit dropping, when of the size of peas or larger, is due to improper pollination. When the soil is not sufficiently well drained at such a time, the sour-sap effect is greatly augmented.

Humidity.—Foggy or moist weather during ripening or harvesting is highly objectionable. The nuts do not dry out rapidly enough on the trees to prevent the growth of molds and consequent darkening of the shells. The nuts then require much heavier bleaching to brighten them properly for the demands of the market. The damp weather prevents the rapid and thorough drying-out of the kernel; the sulphur fumes are absorbed by the moist kernel and it sometimes becomes rancid before it is six months old.

Much damp weather in the spring encourages the growth of “shot-hole” fungus in the blossoms and fruit, often causing the loss of a considerable portion of the crop; the loss of leaf surface from the fungus infection is sometimes so great as to materially affect the vigor and vitality of the tree.

Rainfall.—It is impossible to state any definite amount of rainfall which will or will not maintain the trees and enable them to bear regular crops of nuts, for so much depends not only on the variation in rainfall in different sections and in different years, as regards distribution throughout the year, but also on the time and intensity of the fall, the character of the weather following the rains and the ability of the soil to receive and retain the rain that falls. Ordinarily, however, with the above factors favorable, it is conceded that where the winter rainfall averages sixteen inches, almonds can generally be grown without supplementing the water supply by irrigation, if the orchardist exercises reasonable care to conserve the moisture for theuse of the trees. Where the rainfall is inadequate some means of irrigation must be found to make up the deficit.

In some sections the annual rainfall varies greatly from year to year. Often it falls in such a way that a large proportion of it is lost in the surface run-off. In many places the soil is so leachy that it is incapable of holding sufficient water for the use of the trees throughout the summer, much of the winter rainfall being lost in the underground drainage. Under either of these conditions, 40 inches of rainfall might not be sufficient. Very often winter rains are followed by desiccating winds so that a considerable portion of the rain which falls is lost by evaporation before anything can be done to hold it.

Continued rainy, damp and cold weather at the time of blooming is apt to sour the pollen or actually wash it away and thus prevent the fertilization of the blossoms, without which a crop is impossible. Bees and other insects are the principal means of accomplishing the pollination of almonds and such weather prevents them from working.

The almond is a deep-rooting tree and draws heavily upon the plant-nourishing elements of the soil. In ripening the large number of seeds which it is required to do, the tree must draw upon a considerable area of soil in order to supply the large amount of mineral matter that is needed to develop and mature the seeds. Analyses of almonds, as compared with other commonly grown fruits and nuts, made by Colby,[2]show that the almond leads in the total quantity of mineral matters withdrawn from the soil. Colby further states that “The stone fruits fall much below the almond in total ash (mineral matter) excepting the olive, the ash of which, however, is largely silica (nearly eight-tenths), an ingredient so plentifully distributed in all soils that it is of no pecuniary value.”Table Iillustrates this statement.

These figures suggest the necessity of having a deep, rich, well-drained soil for best results. For this reason and because of the deep-rooting habit of the almond, the soil should be at least ten or twelve feet deep.

Hardpan.—Compacted substrata in the soil, whether they be hard clay layers or cemented layers of silicious, ferruginous or calcareous origin, are objectionable. They not only prevent the roots from foraging to a considerable depth as they normally tend to do, but they prevent proper drainage and aeration of the soil. If such layers arecomparatively thin, that is, not more that two or three feet thick at the most, they may be shattered with dynamite so as to allow the moisture, air and roots to penetrate to the better soil below. Hardpan, therefore, should be avoided where it is too thick to be broken up or where it is not underlaid by desirable soil.

* 80.7 pounds of which is silica.

Humus.—A plentiful supply of humus in the soil is essential. It not only improves the physical condition of the soil, but assists drainage, moisture retention and in rendering the plant food available in sufficient quantities for the use of the trees and for the maturing of full crops of almonds. Many orchards have been very light producers year after year because of a deficiency of humus in the soil.

Drainage.—The almond root is very particular as to its air and moisture requirements in the soil. It will not endure standing water in the soil for any length of time, especially during the growing season. Exclusion of air by excessive moisture is believed to be one of the most productive causes of “sour-sap.” If allowed to continue for any length of time such conditions will cause the death of many or even all the roots and with them the top.

Water Table.—A factor which is very commonly overlooked in connection with the natural drainage of almond lands is the position of the water table at different seasons of the year. Great care must be exercised in choosing a location to be sure that the water table does not rise during the summer. This is a very serious problem in many irrigated sections. Where the water table during the winter months is less than 12 feet in depth it is highly desirable to have as little fluctuation as possible. Where fluctuations take place at a greater depth than 12 feet they are not generally serious. The ideal conditionis where the water table is highest in the winter and quickly drops after the winter rains are over, to a depth of from 10 to 12 or 15 feet, remaining at that point during the remainder of the growing season.

The soil in addition to being well drained, must be sufficiently retentive of moisture to supply the tree throughout a long, dry growing-season. If the soil will not retain a sufficient amount of the winter and spring rains, recourse must be had to irrigation to supply the deficiency.

Alkali.—Alkali lands are unsuited to almond culture and should be carefully avoided.

In summarizing the soil requirements for almond culture, it may be stated that the ideal almond soil is a medium loam, uniform in texture, or nearly so, to a depth of at least twelve feet, well drained and yet retentive of moisture for the use of the tree during the summer. Fortunately some of the best almond soils are situated along stream banks where the land is relatively high, and is, therefore, less subject to frost. These streams flowing from the mountains and foothills have built up their own beds by the detritus brought from the hills. The coarser particles being deposited first and nearest the stream itself, make the better drained soils, while the finer particles and the clays, deposited further back from the bank and in the lower lands, form the heavier soils.

The various conditions mentioned above are what the tree should have for best conditions of growth and production. Oftentimes these conditions may be approached without the soil being as deep as ten or twelve feet. Exceptions to this will be mentioned in discussing the various almond districts of the state. It is essential to understand that trees, while growing and bearing on shallow soils in some localities, do so because of other exceptionally favorable conditions; either the soil is exceptionally well drained and yet sufficiently retentive of moisture, or the humus in the soil is plentiful and the roots are able to work into the underlying partially decomposed rock for moisture and some plant food. In such localities the trees bear comparatively well because of the exceptional freedom from frost in the spring. Trees in these localities are generally smaller than on the deeper, richer soils, and where other conditions are equal, they bear crops in proportion to their size.

Almonds are grown in nearly every county in California. In some counties the few trees growing only occasionally succeed in producing a crop of nuts. There are sections in nearly all parts of the state, however, where they are a success commercially. Within these sectionsmay be found desirable and undesirable locations, depending upon soil and moisture conditions and freedom from injurious frosts. Any discussion of a district, therefore, does not necessarily mean that all lands within that district are uniformly adapted to almond culture. On this account it is impossible to define a district any more closely than to name the center and include with it the outlying districts. In the same way it is sometimes impossible to say just where one district begins and another ends. Adaptability of any special location can be determined only by careful study of the land itself and diligent inquiry of those familiar with it.

As far as possible, districts should be chosen where a definite cold winter season exists. Warm weather and lack of freezing temperatures do not hold the trees fully dormant and any frequent occurrence or unusual continuation of spring weather in the winter will start the trees into growth; cooler weather following, interferes with the normal flow of sap, results in injury to the tree and blossoms, and often causes gumming of the nuts which mature. This condition exists largely in the lower elevations in Southern California and especially in the coastal portion, where the ameliorating influence of the Pacific is felt. This same condition exists close to the coast in the northern portion of the state. Further inland and at higher elevations the winters are more pronounced, and where these are not too severe or prolonged the almond thrives best.

Commencing in Solano County, about eight miles northwest of Suisun and extending as far north as the southern end of Shasta County, close to the base of the foothills on the west side of the Sacramento River, are a large number of orchards on the bottom lands of the valley. These are found principally on the higher lands along the banks of streams flowing from the Coast Range in a generally easterly direction to the Sacramento River. The two most important streams of this type are Putah Creek, forming the boundary between Yolo and Solano counties, and Cache Creek, flowing through the Capay Valley and across Yolo County to the Sacramento River.

These plantings being on the floor of the valley are more subject to frost than the foothill plantings, but they have the advantage of being on the rich valley soils, and while they may lose a crop occasionally from frosts, they make it up in the long run by the much larger growth of the trees and their ability to produce larger yields. Many orchards do not show any such ability to produce large crops, but such a failure must be attributed to lack of pruning and care,rather than to any inherent inability of the large trees to produce nuts. Again, trees on the rich and moist bottom lands may be kept so vigorous and healthy by good care that they are apparently able to endure lower temperatures than less vigorous trees on the shallow and poor upland soils where frosts are less common or severe.

Many recent plantings have been made along the lower foothills on the west side of the Sacramento Valley. The three most important districts where these plantings have been made are west of Dunnigan, Arbuckle and Corning. The plantings in these districts are mostly on a gravelly clay or clay loam soil which is not as rich nor generally as deep as the bottom lands and, consequently, the trees are somewhat smaller, but they have the advantage of freedom from spring frosts due to superior air drainage. The problem in this district is chiefly one of moisture retention by cultivation, as in most cases the growers are unable to get water for irrigation at a reasonable cost, if at all.

The valley districts extend to Tehama County and down the east side of the Sacramento River, the same as on the west side, the principal centers being at Chico, Durham, Liveoak, Pennington and Sutter. Parts of the Liveoak section are too low and many orchards have suffered from poor drainage both of water and air.

The foothill sections on the east side are principally around Antelope, Fairoaks and Orangevale in Sacramento County and the southern end of Placer County. Here the danger from frost is slightly greater than on the western foothills because of the proximity to the snow-covered Sierra Nevada Mountains. On the other hand, water from the Sierras renders irrigation possible at a reasonable cost, so the trees can be kept in good condition. Care must be exercised here to avoid frost pockets. There is also danger of poor soil drainage in the swales.

Conditions here blend very much into those of the Sacramento Valley sections. Continuing south there are plantings around Acampo, Lodi, Stockton, Linden, Ripon, Modesto and more scattered plantings farther up the valley. The danger from spring frosts increases southward due to the earlier blooming of the trees. In some of these sections, notably around Ripon and Modesto, the excessive use of irrigation water for alfalfa and other crops has resulted in a rise of the water table in many places until it is within a foot or two of the surface during the summer months, and in many other places comes to within four feet of the surface.

On the west side of the San Joaquin Valley the principal plantings have been in eastern Contra Costa County. Most of these orchards are of old trees, planted from 15 to 30 years ago. In order to obtain satisfactory air and soil drainage the orchards were planted on the rolling hills, the soil being nearly all blow-sand. Irrigation is too expensive to be installed on most of this land, and the problem in that section is to conserve moisture and at the same time hold the soil in place and prevent it from being carried away by the wind.

Fig. 3.—Typical hillside orchard of Jordan almonds near Los Gatos. Trees are variable in size, and some are missing. In the right foreground is a typical spot of missing trees resulting from Oak fungus infection.

Almonds were planted quite extensively in past years in many of the coast valleys, such as the Santa Clara, and where they were protected from the direct influence of the moist ocean breezes, they apparently did well. Later most of these orchards were replaced by prunes and apricots as they were generally found to be better paying crops in these valleys. On the hills, however, many typical hillside orchards remain, as shown infigure 3.

Localities directly affected by the coast breezes have proved themselves to be unfit for commercial almond culture.

Back from the coast in the smaller valleys and on the hills where the coast fogs seldom reach, many locations may be found where almonds are producing successfully. These favorable localities are scattered, owing to lack of proper soil or moisture conditions.

Paso Robles District.—The one outstanding district in the coast hills where the almond is being grown successfully is in the country west of Paso Robles. There, at an elevation ranging from 900 to 2000 feet, where there is sufficient air drainage to the considerably lower land near by, the almonds are doing well. These plantings are, in most cases, on a comparatively heavy soil, sometimes approaching adobe, and underlaid by marl. This limestone formation is quite permeable to both water and the roots of the trees, and the rock itself acts as a sponge and holds considerable quantities of moisture. On the other hand, consisting of steep hills, the land is excellently drained and the trees seldom suffer from standing water around the roots.

The chief objection is that most of this land is very shallow, generally ranging from two to four or five feet deep. In some places almonds are found growing where the marl is so close to the surface as to be turned up by the plow. This makes the retention of moisture for the use of the trees a serious problem. The trees do not attain large size on such soils and the nuts are inclined to be somewhat smaller than normal. The steep character of much of the land makes tillage and spraying rather difficult and expensive. As long as the price of the land is kept down to a reasonable figure, the grower can afford to put more money into the care of both land and trees. It must be thoroughly understood that there are many localities close to Paso Robles that are greatly subject to frost and hence not at all suited to almond culture. This is especially true of the lands directly around and east of Paso Robles, and also of any of the comparatively low lands throughout the district.

The entire coast district of Southern California has practically proved itself to be unfitted for almond culture, except at elevations above 1500 or 2000 feet. The limiting factor seems to be the lack of a sufficiently definite winter season at the lower elevations. Trees are inclined to bloom too early in the season or before the winter is over.

Above 1500 or 2000 feet the increased elevation gives a sufficiently definite cold winter season and the trees tend to blossom at moreseasonable times. Aside from scattered plantings in the hills of San Diego County and a few orchards around Hemet and San Jacinto in Riverside County, the principal plantings are at Banning and in the Mojave Desert.

Banning District.—Within a radius of three miles of Banning, with an average elevation of 2300 feet, where a plentiful supply of water is to be had from the mountains to the north, are a large number of orchards ranging in age from 2 to 29 years. The bulk of the plantings were made during 1910 and 1911. This is the oldest district in southern California and has proved itself to be well fitted for almond culture.

Antelope Valley and Vicinity.—The old plantings in the Mojave Desert are few and far between. They have, however, served as an impetus for large plantings in recent years many of which have turned out to be failures. This happened in many portions of Antelope Valley, west of Lancaster, on the Southern Pacific Railroad in northern Los Angeles County. Many more of these plantings are young and still have to prove themselves.

Orchard almond trees are never grown from seed, as they do not reproduce true to type, but are propagated by budding desirable varieties on seedling roots in the manner commonly employed in nursery practices for other stone fruits, like the peach. Every grower must decide, however, on what rootstocks he will plant his trees.

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 inFig. 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. Seefigure 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 inFig. 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 infigure 5. A comparison withfigure 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.

Often through injudicious selection of varieties for original plantings, or for some other reason, it becomes desirable to work over old trees to more desirable varieties. This may be done by budding or grafting. In either case the tree may be entirely reworked in one season or one-half may be done the first season and the other half the next. The almond will recover fully if completely deheaded to a height of from five to six feet from the ground, provided it is not subjected to severe winds or excessive moisture in the soil. Winds are liable to break off the new top during the first year or two. Where these are dangerous it may be well to leave half of the tree on the windward side to be worked the second season. The remaining portions will help to serve as a wind-break until the top-worked portion of the tree has a chance to unite solidly with the stub of the main branch to which it is attached. Where winds are not likely to do damage it is generally the most economical method to work over the entire tree at one time. If the roots are subjected to excessive moisture conditions during the first season, the new growth may be unusually vigorous and much more likely to be blown out as a result of the heavy top and the poor attachment to the stub. “Sour-sap” may also be very serious. Under such conditions leaving half the tree the first season will enable it to distribute the growth more evenly with less undesirable forcing.

Whether the top-working shall be done by budding or grafting depends largely upon the wishes of the grower and the skill of theworkman. Grafting will give a new tree more quickly than budding, because by the latter method a year is lost in growing a supply of new wood on the stubs into which the buds must be placed. By grafting, the new scions may start growing the first spring without any delay. Ordinarily the best method is to graft the trees the first winter and then, where the grafts fail to grow, buds may be inserted in the new growth which will come from the stub. During the first two seasons especially, great care must be exercised to keep out the sprouts that interfere with the growth of the scions. At the same time, all water-sprouts should not be removed during the first summer or there will not be sufficient leaf surface to perform the necessary functions of the tree. In addition, the scions tend to grow so rankly that they will be top-heavy and much more liable to be blown out by the wind, as shown infigure 6. This may largely be prevented by pinching the ends of the new scion growth during the early summer to force lateral branching. At the end of the first year all water-sprouts should be removed leaving nothing but the growth from the scions.

Fig. 6.—Twenty-seven-year-old trees deheaded two years before, showing the break-off of the new growth by strong winds.

The usual preparation given land for orchard purposes prior to planting should be applied to land being prepared for almonds. Special care must be given to insure thorough aeration of the subsoil by breaking up all hardpan, plow-pan or other compacted layers in the soil, where possible.

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