Early last year two tubers of this plant were received at Kew from Caracas, and from out of doors in a prepared bed in June. The result of this experiment, together with a few particulars as to the esculent properties of the tubers, may be worth recording, as I believe several gardeners, among them being the Messrs. Sutton, have obtained tubers of the Ullucus from Kew with a view to giving it a trial. The two Caracas tubers mentioned above were as large as hens' eggs, rather longer, and somewhat flattened; the skin was red, as in some potatoes. These, when placed in heat, rapidly developed shoots, which were removed as soon as they were strong enough to form cuttings; in this way about a hundred sturdy young plants were obtained and made ready for planting out of doors in June. They were planted in a light, sandy, well manured soil in a position exposed to full sunshine. Here they grew quickly, forming by the middle of August tufts of shoots and leaves one foot across. They were earthed up as for potatoes, and the strongest shoots were pegged down and partly covered with soil, though the latter proved unnecessary. At this time there were no tubers nor any signs of them.
On again examining the plants in September (about the middle), we were surprised to find no tubers had yet been formed. The plants were now very strong, and it was therefore concluded that instead of forming tubers the strength of the plants had "run to leaves." We gave them up, no further notice being taken of them till the frost came, when on perceiving that a frost of four or five degrees did not injure the foliage, we again examined the plants, and found an abundant crop of tubers just below the surface of the soil, and varying in size from that of peas to pigeons' eggs. The plants were left till the haulms had been destroyed by cold, after which the tubers were gathered. On cooking some of the larger ones by boiling for half an hour, we found them still rather hard, and with a flavor of potatoes, almost concealed under a strong earthy taste, quite disagreeable and soap-like. Considering how short a time these tubers had had to grow in it is not improbable that their hardness and disagreeable taste were owing to their being unripe; no doubt young, green potatoes (these Ullucus tubers were partly green) would be quite as nauseous as these were.
We are told that the Ullucus is extensively cultivated in Peru and Bolivia, in the elevated regions where the common potato also thrives, and with which the Ullucus is equally popular as a tuber-yielding plant. In the Gardeners' Chronicle for 1848, p. 862, Mr. J.B. Pentland stated that the Ullucus "is planted in July or August, the seed employed being generally the smaller tubers, unfit for food, and is gathered in during the last week of April. These two periods of the year are the spring and autumn in the southern hemisphere. The mode of cultivation is in drills, into which the root is dropped, with a little manure. The climate, even during the summer season, is severe, scarcely a night passing over without the streams being frozen over, the sky being in general cloudless at all periods of the year except during the rainy season (December to March). Mean temperature about 49°." This information seems to support the view formed of this plant from its behavior at Kew last year, namely, that the tubers are formed on the approach of cold weather, and that, so long as the weather is warm and bright, leaves only are developed. Plants grown in houses where the temperature has not been allowed to fall below 50° in winter did not form any tubers, although they were in good health.
We found no tubers on the plants grown out of doors till some time after the return of cold, wet weather. It seems likely that this plant does not develop tubers unless its existence is threatened by cold; at all events, such a conclusion seems reasonable from the above statements.
Possibly a wet and rather cold autumn would be favorable to this plant and the production of its tubers - such a season, for instance, as would be most unfavorable for the common potato. It would be worth while testing the Ullucus for low and cold situations where the potato would not thrive. There is not much probability of the former ever proving a substitute for or even a rival to the potato, at least in this country; but there is room for another good esculent, and the Ullucus is prolific enough, hardy enough, and, we suppose, when properly grown, palatable enough to be worthy a trial. In the Gardeners' Chronicle for 1848, p. 828, will be found a most interesting detailed account of experiments made with this plant in France by M. Louis Vilmorin. - W. Waston, Kew; The Gardeners' Chronicle.