This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
THE Onion is referred to as a popular vegetable at a very early-period of the world's history; and it is perhaps a vegetable that is more universally cultivated than any other that is embraced in garden-cropping. It is cultivated by hundreds of bushels for royal households, and to a proportionate extent it finds a place in every grade of garden down to the cottage "yard." Although extensively grown in Britain, so great is the consumption of it, that more than a thousand tons are annually imported, principally from Spain and Portugal, in which countries it is an important article of commerce; for, beyond what is brought to this country and sent to others, it is a vegetable which is much more extensively consumed by the Spanish and Portuguese than is common in this country; in fact, it forms for them an important part of their daily meals. Onions are esteemed, in the first place, on account of their flavouring quality. They are at the same time among the most nutritious of vegetables - containing, as they do, 30 per cent of gluten, the presence of which in vegetables determines more than anything else their value in point of nutriment.
It is therefore probable that the Portuguese is as well off, in point of nutritious aliment, with his dry bread and Onion, as the English labourer is with bread and cheese.
The Onion is a vegetable of great antiquity in Africa, having been cultivated and much esteemed there two thousand years before Christ; and in the food of the Egyptians it still holds an important place. They roast them along with their meat, and relish them so much that they are credited with the earnest wish that Onions may form one of the dainties of their paradise. This vegetable has been cultivated from a very early period in Britain; and more than likely it was introduced from Continental countries, into which it had no doubt been brought from the more ancient nations of the East. Onions grown on the Continent are much more mild and pleasant to the palate, but not so good for seasoning, as the smaller productions of this country, which are more pungent in flavour.
The Onion crop is looked upon as one of first-rate importance in every garden, and the sowing-day ranks as a sort of red-letter day in the garden calendar. Many cultivators have some peculiar way in which the operation is performed; and in not a few cases a deal of unnecessary work and waste of time are attached to it. Few crops are more affected by soils and situations; hence in some instances a satisfactory crop can nearly always be calculated upon, while in others the crop is a very precarious one.
A dry well-worked soil, to the depth of at least 2 feet, has much to do with healthy well-matured bulbs. They send their roots down deep; and if the staple allows of the ground being worked 3 feet deep, so much the better. It is more upon a deep well-worked dry staple than on superfluous doses of manure that a good well-ripened crop of bulbs depends. Such bulbs as are small-necked, firm, and in a condition to store and keep well, are not so likely to result from heavy coatings of manure merely dug into the ground, as from a moderate amount of manure, in a thoroughly decomposed state, deeply and regularly mixed with the whole of the soil. The Onion crop makes a good succession to Celery, or rather the latter leaves the ground in good condition for the Onion crop. The production of good Celery necessitates a thorough breaking-up of the ground; and the liberal application of manure required for the one, when thoroughly mixed with the ground, is almost enough for the Onion crop. The ground should be trenched across the old Celery trenches, and the manure well broken up and thoroughly mixed with the staple as the operation goes on.
The trenching should be performed early enough to allow the ground to benefit from it, which usually occurs in January and February. It is well to ridge the surface or leave it rough, presenting a large surface to the action of the atmosphere. The two bottom-spits, on the other hand, should be well broken, and the subsoil forked up and left in the bottom.
Situation is a matter of considerable importance - shelter from high winds, and exposure to the sun; for if the tops get damaged by wind before the perfecting of the bulbs, they do not swell nor ripen properly; and shade from the sun by trees or walls has the same effect. If the soil and situation be damp and low, it is a good plan to throw the ground into beds running north and south, and to raise them by throwing the ground out of the alleys on to the beds, as is often practised in growing Potatoes in what are termed lazy-beds. The Onion, to grow and bulb well, likes a warm sunny situation and a somewhat tenacious loamy soil, well drained. Light sandy soils are not likely to produce fine Onions; and to improve these, heavier soil is often mixed with them. Light soil should also be well trodden and rolled both before and after the crop is sown.
Local peculiarities of soils and climate should regulate - within certain limits, of course - the seed-time of the Onion, and not days and dates. There is nothing gained by early sowing in wet localities and heavy cold soils. Under such circumstances, the middle or end of March is sufficiently early; while on friable loamy soils and in earlier localities I have always taken the first favourable opportunity of sowing after the 20th February. A fortnight or more time is of no consequence as compared to the state of the soil; and it is better to wait than to sow when the surface is wet and in bad condition.
On very light, dry, shallow soils, where the crop has a tendency to ripen off very small and prematurely when overtaken by droughts, such as have occurred the two last summers, it is a good plan to sow part of the crop at least in autumn. The first week in September is a good time to sow; if sown earlier they get too strong, and are all the more likely to run to seed in spring. The advantage of sowing in September on such soils is,- that the Onions are much earlier and further advanced in size before hot dry weather sets in to stunt and ripen them before an ordinary size is attained. Another plan, sometimes practised on poor shallow soils, is to sow thick on poor soils, and considerably later than is usual for spring sowing. A crop of very small bulbs is thus produced; and these, carefully wintered and planted on well-enriched soil 6 inches between the rows and 4 inches between the bulbs, produce fine crops. In Portugal they sow thickly in beds in November, and transplant them in spring on to very rich soil; and in this manner their fine large bulbs are produced. All other things being equal, the size of the bulb is largely affected by the amount of room allowed to each.