ECONOMIC PLANTING. Windbreaks. The protection afforded by windbreaks must be reckoned an important factor in the horticultural development of California. The necessity of windbreak protection in many sections of the State is so great that without it certain crops can not be raised. Many trees are suitable for windbreak planting, yet California farmers are united in the opinion that Monterey cypress is the only competitor of blue gum and other eucalypts for this purpose. The eucalypts excel other species in their towering height and rapid growth, thus affording a protection most quickly. The trees are slender and open-crowned, but double rows of trees or close planting provide a strong check against the wind. The blue gum surpasses all others for this purpose, and should be used throughout its thermal range. Its tall, limber shafts yield before the wind and act as a cushion to deflect the air currents upward over an orchard, while ordinary windbreak trees form a solid wall on the leeward side of which the wind draws down and forms eddies. In the open valleys of Southern California Eucalyptus windbreaks have become a prominent feature of the landscape and their presence is recognized as indispensable to successful orcharding. To their protection may be attributed in large measure the fine quality of the California citrus crop, and in this way these trees return vast sums annually to the State. In citrus sections, such as the Santa Paula, San Fernando, San Bernardino, San Gabriel and Santa Ana valleys, windbreaks alone render the production of citrus fruits profitable. In unprotected orchards, nearly the entire crop is frequently blown from the trees, or so scarred and bruised that the grade and market value are much reduced. Orchard trees are even broken or partially defoliated during severe storms. To avert this danger and improve the grade of fruits, windbreak planting is being greatly extended even in old citrus sections. More extensive shelter-planting is advisable in many sections of the State, notably in the Sacramento and San Joaquin valleys. Hitherto windbreaks have been used chiefly to shelter citrus orchards, but now they are coming into favor to shelter vineyards, deciduous orchards, olives and walnuts. Much more extensive development may be attained by their use in sections where strong or cold winds are felt. Along the coast, shelter from sea winds is found to increase the yield of grain crops. Eucalyptus windbreaks in some sections have changed the aspect of the country and by moderating the winds have greatly improved the climate. Waste, sandy, stretches have been turned to productive agricultural use. In the region of Oxnard the towering windbreak lines hold the loose sand from drifting before the steady sea winds, and the region has thus become, largely through their agency, an important center of sugar-beet production. Trees PLATE 6. Avenue planted with blue gum trees in San Bernardino Valley. Along the coast the planting of shelter belts for the protection of towns has been practiced to some extent, to the greater comfort of the resident population. This branch of shelter planting should be extended particularly on the windward side of seaport towns, where windbreaks in proper places will protect anchored vessels and facilitate shipping. Windbreak planting should also be practiced in many coast localities to hold the sand from drifting inland and covering up valuable agricultural land, crops and dwellings. Fully grown Eucalyptus windbreaks running at right angles to the direction of the prevailing winds every quarter mile across level country afford effective protection. Near the foothills the lines should be closer together, since the winds blowing down from the mountains gain greater velocity. Through orchards they are generally located every 100 or 200 feet. Though a heavy wind may be swaying the tops of the trees in a windbreak, usually there is hardly any stir in the air near the ground within a well-protected citrus orchard. The wind is never sufficiently strong to whip the foliage or injure the fruit. All crops protected in this way suffer less from winds than opengrown crops. They remain uninjured when unprotected crops are blighted, unless the arrangement of the windbreaks results in defective wind-drainage and the formation of a frost hole. After a cold night, during frosty winter months, the shade cast by a windbreak on the eastern side of an orchard will often prevent injury from too rapid thawing. Citrus trees are unfavorably affected by shade, hence the yield of fruit of rows adjoining a windbreak is often lessened. Windbreaks on the north and east sides of an orchard are less harmful than on the west or south side. Under ordinary conditions the south side of an orchard should be left open for wind-drainage. The best spacing of gum trees for windbreaks is 4 feet apart each way in double rows. The trees of the second row should be planted opposite the open spaces in the first row. Double, or even triple, rows should be planted where the winds are severe. Triple rows will always be adequate for crop protection, though shelter belts from 10 to 20 rows wide may be advisable to protect from strong sea winds. Monterey cypress is frequently planted alternately or in double rows with eucalypts to maintain a dense shelter near the ground, since the gum trees clear the lower stem with later growth, giving access to the winds. This combination is an excellent one, since great density is united with towering height. The cypress is well adapted to this use by its tolerance of shade. Cypress and eucalypts should be planted in separate rows and not alternated in the same row, the cypress being located on the windward side of the line, excepting on the north side of a field, where it should be planted on the south side of the line to receive more light. On irrigated land trees are not compelled to root deeply for moisture, hence they maintain a very shallow root system. If a Eucalyptus windbreak surrounding irrigated land is not irrigated, its roots will extend to adjoining orchards and appropriate moisture from them to supply its own needs. The area drawn upon depends upon the size of the windbreak, but usually it is not greater than 50 feet each way. To prevent this, wide root extension must be limited and the sheltering trees forced to root into deeper soil layers. This can be accomplished without injury to the shelter belts, by running a parallel trench 6 to 10 feet from them. The trench should be dug 3 or 4 feet deep, cutting off the surface roots of the gum trees, then refilled to prevent the roots from dipping beneath it to seek the orchard. The roots will then spread out in the loosened soil of the trench, which should be reopened about every second year to restrain their extension beyond it. The result is to compel deep rooting, which is attested in numerous orchards by the heavy production of citrus trees in rows adjacent to the windbreak. Commercial Plantations. With the exception of a few small, scattered groves of black locust, planting for timber production in California has been confined to the eucalypts and chiefly to the blue gum. This species has been grown extensively in Southern California for fuel, and except for small amounts of oak, juniper, mesquite and pine has supplied the section for the past thirty years. The returns on investments in Eucalyptus plantations have been generous, in many cases exceeding those received from equal areas under cultivation in orchards or agricultural crops. Groves set out in the fertile Los Angeles valley have yielded from 50 to 80 cords per acre at every cutting. Yields of 75 cords per acre every seven or eight years have been frequent. At the present time there are several thousand acres in California planted to Eucalyptus. The following is a partial list of the larger fuel |