Apple

I

Introduction

Apple, common name for certain related trees of the rose family, and for the pome fruit of the trees. The apple tree, a deciduous plant, grows mainly in the temperate areas of the world. The fruit is a firm, fleshy structure derived from the receptacle of the flower. Apple leaves are broadly oval in shape and are somewhat woolly on the undersides. The flowers in bloom have a rounded appearance. Some apple blossoms are white, but the majority of apple blossoms have stripes or tints of rose. A few apple species bloom with bright red flowers. Apple wood is hard, durable, and very fine-grained.

The physical characteristics of the fruit are subject to considerable variation. The skin color may range from green to a deep, blackish red. Shapes, also, are diverse and include oblate and oblong fruits and fruits of a size hardly larger than a cherry or as big as a medium-sized grapefruit.

II

Varieties

Apple trees have been cultivated for their fruit for many centuries. Early apple growers selected superior strains from wild seedlings and propagated them by grafting. Currently, many apple varieties are developed by controlled crossing of desirable parents. Beneficial mutation in standard varieties is also a source for new varieties. It is generally thought that modern apple varieties resulted from natural cross-pollination involving several species because modern varieties are heterozygous—that is, they do not reproduce true to type.

Apple trees are best adapted to areas in which the average temperature approaches or reaches freezing during at least two months. The exact chilling requirement varies somewhat with each variety. The trees withstand temperatures down to -40° C (-40° F).

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III

Culture

Apple growing is a highly specialized business and the trend is toward larger orchards, especially because costly mechanical sprayers have been used to control diseases and insects. Leading diseases of apples are apple scabs, mildew, and fire blight. Insect pests include the codling moth, the apple maggot, the red-banded leaf roller, aphids, leaf hoppers, mites, San José scale, and oyster-shell scale. Rodents, particularly pine and meadow mice and rabbits, cause severe damage to trees unless proper control measures are employed.

Several horticultural methods are used in apple culture. One system is based on clean culture, with winter cover crops sown throughout the orchard; another method utilizes permanent sod and sod mulch. If a permanent grass or sod system is used, additional fertilizer is needed to compensate for organic nutrients absorbed by the grass. If clean culture is practiced, no additional cultivating is advisable after the first week in August, in order to permit the trees to harden off—that is, to become adapted to the lower temperatures of fall and winter.

Apple trees are vegetatively propagated by grafting or budding. By these methods a scion (bud of the desired variety) is inserted into the base of the stem or trunk of a seedling tree known as the stock. Sometimes the stock itself is a vegetatively propagated tree. Most trees are propagated, however, on seedling rootstocks. Several size-controlling rootstocks are available. Uniform heights facilitate spraying and harvesting. Extremely dwarfed rootstocks are popular where space is limited.

Most apple varieties require cross-pollination in order to bear satisfactorily. Certain varieties, known as triploids, are of no value as pollinators because of their genetic makeup. Two diploid pollinating varieties must be present to pollinate each other as well as the triploid variety.

IV

Production

Commercial apple production in the United States is limited to about four favored areas: the northwestern states, the Shenandoah-Cumberland region, the northeastern states, and the north-central states. The northwestern area is noted for high yields but uses extensive artificial irrigation.

Of the several thousand varieties of apples, relatively few have commercial importance. Delicious, with its color mutations, is the most widely grown variety in the United States. It is particularly well adapted to the northwestern United States but is grown commercially in all apple areas. McIntosh is the leading apple in the northeastern United States. In the Shenandoah-Cumberland area the most important orchard varieties are York Imperial, Delicious, and Stayman Winesap. Varieties adapted best to the north-central area are McIntosh, Jonathan, Rome Beauty, Wealthy, and Cortland. Eastern Canadian apple growers cultivate nearly the same varieties as those grown in the northeastern United States. British Columbia is best suited to the varieties grown in the Northwest; McIntosh, however, is a favorite among British Columbian orchardists.

World production of apples was 57 million metric tons annually at the beginning of the 21^st century, led by China, the United States, and Turkey. The leading apple-producing countries in Europe are France, Italy, Poland, and Germany; most of the crop is processed as either cider or brandy. Apple production in the United States at the beginning of the 20^th century was about 7 percent of the world total. Washington is the most important apple-producing state of the United States. Next ranking in descending order are New York, Michigan, California, Pennsylvania, and Virginia.

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