This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The Parsnip (Pastinaca sativa) has been grown since Roman times, and has no doubt been derived from the Wild Parsnip of Europe and Britain. Indeed this has been proved by Professor James Buckman, who in 1848 sowed seeds of the wild plant, and succeeded in obtaining three distinct forms by selection in four or five years. One of these was introduced to commerce in 1860, and is still popular under the name of "Student". It has a concave or hollow crown, and is thus distinct from the common form, which has a convex, rounded crown.
It seems strange that such an important market-garden crop as the Parsnip should not be mentioned in the Returns of the Board of Agriculture. It is probably lumped with "other crops". The Department of Agriculture and Technical Instruction for Ireland, however, takes notice of it, and for the year 1908 records 641 ac. as being grown in Ireland, Leinster having 318 ac, and the county of Dublin 157 ac. The total yield is given as 7238 tons, being an average of 11.2 tons per acre. This is a poor crop, so far as weight is concerned, for such a heavy plant as the Parsnip. As the plants are usually grown in rows about 15 in. apart, and about 9 in. apart in the rows, there would be about 43,560 roots to the acre if there were no gaps or failures. As anything like a Parsnip will weigh at least 1 lb., there should be about 19 tons per acre under favourable cultural conditions. Even if 25 per cent is deducted for failures, the crop would come to at least 14 tons. [J. W].
This important crop has three advantages - it affords a change from the large family of vegetables liable to club; it remains in the land without injury from frost all the winter; and, finally, being a deep-rooted crop, the physical effects of the roots forcing their way down into the subsoil and of their swelling in the soil are very valuable.
Stable manure is not to be recommended in preparation for a crop of Parsnips; it is apt to leave the land hollow and to encourage the formation of "chumps" in the place of straight-rooted plants. The land, however, should be deeply subsoiled, and the previous crop should have sufficient manure to leave the land in good heart. If manure at all is needed for the Parsnip crop a good compounded ordinary market-garden chemical manure may be used, or the land may be dressed with 4 cwt. of agricultural salt and 5 cwt. of dissolved bones to the acre, sown on the furrow before the land is worked down.
Fig. 482. - Parsnips - "Tender and True ".
The drills are put 15 in. apart, and 10 lb. of seed is enough for an acre, and the seed should not be put deeper than 1 in.
As soon as the young plants have made their third leaf the thinning to a distance of 9 in. in the rows should be done, and done quickly. If the plants are allowed to stand thick long enough to draw each other, they will never quite recover from the weakness and check in consequence.
Parsnips will not do well in shallow soil or chalk, nor in very stony soil; otherwise the crop is so valuable as a change that it is wise to grow as much of it as can be disposed of. But as it is one the sale of which cannot be forced, the grower must feel his way as to the quantity to grow, for although the Parsnip makes good food for stock, if more is grown than can be sold on the market, the cost of digging and disposing of the surplus will make a serious inroad into the profits earned by what has been sold. A crop of Parsnips will cost about £3 an acre for hoeing. The price for best is generally 5d. to 6d. per dozen; for seconds and "chumps" about 2s. per cwt. Lisbonnais, The Student, Magnum Bonum, Maltese, and Tender and True are good varieties.
The Parsnip is frequently attacked by the Celery Fly, which lays its eggs between the upper and lower surfaces of the leaf, the grub, when hatched, eating out the substance of the leaf.
One or two sowings of soot will make the plants too unpleasant to the flies, and they will seek some other host for their purpose. [W. G. L].