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.
Both Salsafy and Scorzonera require precisely the same treatment, consequently I have classed them together. There are few vegetables so much affected by cultivation, "for better or for worse," as these, and at the same time so carelessly regarded. True, the entire failure of a crop is not of frequent occurrence, for they will grow after a sort under the most careless treatment; but the difference between really well cultivated samples of these roots, and those produced by indifferent culture, is exceedingly marked.
A superior crop depends chiefly on the nature of the soil, and particularly on the manner in which it is prepared. To produce fine roots, a deep sandy loam is the best; it' should be trenched, and thoroughly broken to at least a depth of 2 feet; and the subsoil, if retentive, should be broken up with a fork. Soil into which manure has been put for successive years, and by which the top spit has been enriched, should not have any manure added to it, but be trenched, turning the rich surface-soil to the bottom of the trench. Where manure is necessary, it should be mixed in the bottom of the trench, not adding any to the surface-soil. The manure thus placed deep in the ground entices the roots in search of it, and in this way considerably influences the growth of the roots, causing them to grow straight and strong, instead of producing a mere bunch of fibres, scarcely fit for culinary purposes, as is the case in shallow soil, with the manure near the surface.
Sowing the seed too early must be avoided, or the crop will run to bloom and the roots become hard and useless. The end of April, or, in places where there is generally a good autumn growth, May is early enough to sow. The Salsafy should be in drills 3 inches deep and 16 inches apart Scorzonera should be allowed a few inches more, as its tops are more bulky. When thinned, 6 to 7 inches between each plant is close enough to leave them. It is not a rare occurrence to meet with these vegetables sown thickly and never thinned out at all, but they are as much improved as Carrots, or any similar crop, by being allowed room; and the reverse of this can only result in very inferior roots. Really well-grown roots are much esteemed in winter, and, manipulated by good cooks, both these vegetables form palatable dishes.
The after-treatment is very simple, and consists of keeping the ground between the rows well stirred and clean. Being winter vegetables, they are seldom asked for till November; and as they are very hardy, the roots may be left in dry soils, covered over with litter, and dug up as required, or they may be lifted and laid away in damp sand under cover. D. T.
I am very much pleased to see "D. T." telling us how to grow these two excellent vegetables, the culture and use of which are so little understood in England. On the Continent they are very much used, and, with a mutton-cutlet, either of these vegetables makes up a most enjoyable supper. My object in writing to you is, to ask "D. T." or some other correspondent to tell us how these vegetables are dressed on the Continent; and this information can easily be gleaned from some chef de cuisine in a large establishment. A boon will be conferred on myself and many others if this information can be given to us.