Trans. of the Horticultural Society of London 1: 57-49 (1820)
IX. On raising new and early Varieties of the Potatoe.
By Thomas Andrew Knight, Esq. F. R. S. &c.
Read January 6, 1807.
THE Potatoe contributes to afford food to so large a portion of the inhabitants of this country, that every improvement in its culture becomes an object of national importance; and thence I am induced to hope that the following communication may not be unacceptable to the Horticultural Society.
Every person who has cultivated early varieties of this plant, must have observed, that they never afford seeds, nor even blossoms; and that the only method of propagating them is by dividing their tuberous roots: and experience has sufficiently proved, that each variety, when it has been long propagated, loses gradually some of those good qualities, which it possessed in the earlier stages of its existence. Dr. HUNTER, in his Georgical Essays, I think, has limited the duration of a variety, in a state of perfection, to about fourteen years; and probably, taking varieties in the aggregate, and as the plant is generally cultivated, he is nearly accurate. A good new variety of an early Potatoe is therefore considered a valuable acquisition by the person who has cne good fortune to have raised it; and as an early variety, according to any mode of culture at present practised, can only be obtained by accident from seeds of late kinds, one is not very frequently produced: but by the method I have to communicate, seeds are readily obtained from the earliest and best varieties: and the seeds of these, in successive generations, may, not improbably, ultimately afford much earlier and better varieties, than have yet existed.
I suspected the cause of the constant failure of the early Potatoe to produce seeds, to be the preternaturally early formation of the tuberous root; which draws off, for its support, that portion of the sap, which, in other plants of the same species, affords nutriment to the blossoms and seeds: and experiment soon satisfied me that my conjectures were perfectly well founded.
I took several methods of placing the plants to grow, in such a situation, as enabled me readily to prevent the formation of tuberous roots; but the following appearing the best, it is unnecessary to trouble the Society with an account of any other.
Having fixed strong stakes in the ground, I raised the mould in a heap round their bases, and in contact with them: on their south sides I planted the Potatoes from which I wished to obtain seeds. When the young plants were about four inches high, they were secured to the stakes with shreds and nails, and the mould was then washed away, by a strong current of water, from the bases of their stems, so that the fibrous roots only, of the plants, entered into the soil. The fibrous roots of the Potatoe are perfectly distinct organs from the runners, which give existence, and subsequently convey nutriment, to the tuberous roots; and as the runners spring from the stems only of the plants, which are, in the mode of culture I have described, placed wholly out of the soil, the formation of tuberous roots is easily prevented; and whenever this is done, numerous blossoms will soon appear, and almost every blossom will afford fruit and seeds. It appears not improbable, that, by introducing the farina of the small, and very early varieties into the blossoms of those of larger size, and somewhat later habits, moderately early varieties, adapted to field culture, and winter use, may be obtained; and the value of these to the farmer in the colder parts of the kingdom, whose crop of Potatoes is succeeded by one of Wheat, would be very great. I have not yet made any experiment of this kind; but I am prepared to do it in the present spring.