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.
To obtain good Parsnips the seed requires to be sown as soon in the year as the soil is in good working order. We generally manage to get ours in some time in February, and never later than the middle of March if we can help it. At the same time, Parsnips can be secured although the seed be not sown until April, but never so fine as those sown earlier, unless under very exceptional circumstances. There is no fear of the seed on the score of hardiness, as in the case of the Beet; and no fear of it running prematurely to seed, as in the case of the Carrot and Turnip, - so that it can be sown as soon as the soil is friable and dry. And perhaps it may not be out of place here to call the attention of young gardeners to the above facts, for it is the custom of some to sow their Carrots, Parsnips, and Beet on the same day; and the consequence is, that the Parsnips do not grow to so large a size as when sown earlier, while it is not an unfrequent occurrence for a large proportion of the Carrot and Beetroot crops to run to seed when sown too early, which of course renders them unfit for use.
The finest Parsnips are raised in deep, rather light soil, in good condition, but having no fresh manure added. The very large Parsnips seen at exhibitions are grown in very rich soil; but these are rather coarse compared with those grown in soil only moderately rich. The soil should be trenched or dug as deeply as possible during autumn or winter, to get it into as free and friable a condition as early in the season as possible; but no manure should be added - presuming that the ground was manured for the previous crop. In spring the first opportunity that occurs should be seized upon for breaking the surface of the soil finely with a fork, sowing each row as the digging proceeds, so as to-prevent the necessity for treading on the soil afterwards. At the same time, we have raised fine crops in light soils by merely levelling the ground with a Dutch hoe, drawing the drills, and raking the surface smooth. This, of course, necessitates a good deal of treading on the soil; but when the soil is sandy and dry, the treading is beneficial rather than otherwise, which is not the case when the soil is heavy.
The nature of the soil must determine which of the two ways ought to be adopted.
Draw the drills 18 inches apart, and as deep as will allow of the seeds being covered to the depth of an inch. Scatter the seeds so that they will not be thrown together in heaps, otherwise there will be great difficulty in thinning them. As soon as the plants can be observed, run a hoe between the rows, for the double purpose of killing the weeds and loosening the surface-soil. As soon as they have formed two rough leaves thin them carefully, leaving them six inches apart in the rows. Their after-cultivation merely consists in clearing them of weeds, and in keeping the surface of the soil well loosened with the hoe. They are ready for use whenever large enough, but do not attain perfection until frozen through. They may be allowed to stand where they grow during winter, as no amount of frost will injure them; while lifting and storing them, as is usually done, spoils them a good deal - so much so, in fact, that we have known them refused by those who otherwise were very fond of them.
To grow them clean, straight, and large for exhibition purposes, a good plan is to trench a deep, rich piece of soil 3 feet deep or so. Put a layer of well-decomposed manure in the bottom of the trench. Afterwards, when the soil is frozen on the surface, drive a strong sharp-pointed stake at intervals of nine inches in the line down to the bottom of the trench, and fill in the holes with fine light rich soil, made moderately firm to prevent it sinking more than the surrounding surface, and sow a patch of seeds on the top; and when to remove all but the strongest.
 
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