Fortunately, it is possible to select varieties suitable to a wide range of climatic conditions. The most tender sorts of the foreign types, as the Bermuda onions, thrive in some parts of Texas, Florida and Southern California, and do well at the North when started under glass. They often, too, produce excellent crops when sown in the open, under the most favorable conditions. All the American varieties thrive in the northern states, and with proper culture generally do well in the South. The multipliers or potato onions are thoroughly at home throughout the South, and with some winter protection may be grown for early bunching in the North. The Egyptian or Perennial Tree onion is hardy in the North, even without protection.
While this vegetable may be grown successfully under a wide range of climatic conditions, it succeeds best in temperate regions without great extremes of heat and cold. When grown in the far South, as in Texas, advantage is taken of fall and winter. The crop is planted in September and harvested in March and April. From 130 to 150 days are required to mature bulbs of the various varieties. A bountiful supply of soil moisture is necessary early in the season, when the plants make very rapid growth. A dry soil and low humidity are important for ripening, harvesting and curing the bulbs.
Land to be used in growing onions should be practically level to prevent damage from washing. The seeds, sets, or young, shallow-rooted plants are easily washed out on sloping lands. The soil should be retentive of moisture and yet well drained, friable, easily worked, fertile and free from stones and rubbish which would interfere with the proper use of drills, hand and wheel hoes.
Vast areas of muck and peat soils are devoted to the culture of onions. The crop is doubtless grown at less expense in these soils, which abound in vegetable matter, than in other types requiring more manure and fer-tilizer and a greater expenditure of labor. Their dark color causes them to warm up rapidly in the spring, and thus they favor early planting, which is universally regarded as important. These soils, rich in organic remains, retain moisture, so that drouth seldom curtails the crop to any great extent.
Sandy loams, when properly enriched with humus and plant food, furnish excellent conditions for onions. They are easily worked and produce solid, heavy bulbs of superior keeping quality.
Clay soils should be avoided. They become too hard and compact for best results. Clay and alluvial loams, when properly "handled, yield profitable crops, but the supply of humus must be liberal to prevent serious baking. Incrustation is especially damaging when it occurs before the plants are up or large enough to permit thorough tillage.
Inferior seed is the source of heavy and frequent losses in onion culture. Onion seed must be fresh, never more than a year old and produced from bulbs of a superior character. Some seed firms have established reputations for selling high-grade seed of this vegetable, and growers should exercise extreme care in ascertaining the best sources of supply.
While it is less difficult at present to procure good seed than formerly, a large number of gardeners and onion specialists raise their own seed. The bulbs are best selected at harvest. They should be of the desired size and form. A short neck is considered an advantage. Uniformity in all of the essential characteristics is exceedingly important in choosing bulbs for seed purposes. Seed bulbs should be stored as directed in this chapter (541) and planted as early as possible in the spring. (Some growers prefer fall planting.) The ground should be only moderately fertile, especially in nitrogen. Furrows are made 4 or 5 inches deep and 14 to 30 inches apart, depending upon the method of cultivation. After placing the bulbs about 6 inches apart in the bottom of the furrow, they are covered with a hoe or a small plow. The long, slender seed stalks should have some support, which may be provided in two ways: (1) By ridging with soil to the height of 7 or 8 inches, the usual plan, and (2) by driving stakes at the ends of the rows and at frequent intervals and then stretching cheap twine on either side. When mature or ripe the heads turn yellow. At this stage they should be removed promptly with 6 to 8 inches of the stalk before any seed is lost. As the tops do not ripen at the same time, it is necessary to make several cuttings to prevent loss. A tight vessel, or basket with a cloth lining, should be used in collecting the seed. The tops are spread in an airy room with a tight floor until dry enough to separate with a flail or by other means. Winnowing will remove most of the chaff. The seeds may then be placed, a few pounds at a time, in a vessel of water. The heavy seeds, which sink, are saved, while the light ones and the remaining chaff are poured off. After thorough drying and curing, the seeds may be stored in any dry room.
The method of soil preparation will depend mainly upon the character of the soil, and the crops previously grown. Fall plowing is often an advantage, especially for pastures, heavy sods, muck lands and clay loams. A favorite practice before planting any field in onions for the first time is to grow the previous year a crop, such as potatoes or corn, which requires thorough cultivation. Coarse stable manures may also be used the year before planting onions. Such a course of treatment will rid the land of troublesome weeds and increase the supply of humus. Rotation is highly desirable, as it is a means of reducing loss from fungous diseases and insect pests and of maintaining proper soil conditions. Other vegetables, as spinach, celery, beans, lettuce, etc., may be used with profit. The selection of the other crops in the rotation must be determined by market, soil, moisture, climate and labor conditions.
Whatever crops are grown previous to planting onions, the soil preparation must be thorough. If plowing is deferred until spring, this operation should be attended to as soon as the ground is sufficiently dry, followed by repeated harrowing, to prevent the escape of soil moisture and to prepare a fine seed bed. The usual forms of disk harrows, followed with the Meeker Disk Smoothing Harrow and finished with a plank drag should leave the land fine, even and smooth.
Muck soils, to be used for the first time, require special preparation. They must be cleared, drained and thrown up to the exposure of winter freezing. Although analyzing high in plant foods (401), large amounts are not available. Lime will help to release the needed plant food and to correct any soil acidity that may exist. It is generally desirable to grow other crops for a season or * more until proper soil conditions have been secured.