This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
I notice, in the June number of the Horticulturist, an article from the pen of C. E. Goodrich, upon the culture of Sweet Potatoes. In that article I notice one error, which ought not to pass without correction. He says: "Dig as soon as the vines are killed by the frost." On the other hand, our most experienced and successful cultivators say that the slightest frost must be carefully guarded against, especially if seed be an object, as the frosting of the vine increases the liability of the tubers to rot I have no doubt the "dry rot," of which Mr. G. complains, is the result of the frosting which he permits. If it is not convenient to remove the tubers from the ground previous to early frost, their separation from the vines may be effected by passing a sharp knife between them, just above the surface of the ground. W. J. Townsend, Zanesville, Ohio.
Although sweet-potato-growing may be regarded as a crop for the South, yet their culture is simple, and the crop in many sections of the Northern States a very remunerative one. Sandy soils are best suited to their growth, but any good loam, well drained, will answer. The ground should be well manured with old, rotten manure, and plowed three or four times before planting. The sprouts may be grown by placing the potatoes in a hot-bed having only a gentle heat, and covering them about two inches deep. When the sprouts have grown from four to six inches, pull them from the potato by slipping the thumb and finger down between the tube and sprout. About the 20th of May or 1st of June is the best time to plant out, previous to doing which the ground should be thrown up into ridges or hills, about eighteen inches high, and the plants set, if in hills, two plants in a hill, and if in ridges, one plant about every two feet on the line.
Covering the ridges or hills with finely-pulverized charcoal, we once saw practiced with the greatest success. It increased the heat in the soil, and at the same time appeared to retain steady moisture.
Keep the hoe and rake going; well-stirred soil absorbs dew and retains moisture longer than that left hard and unstirred.