This section is from the book "The Florist And Garden Miscellany". Also see: All New Square Foot Gardening: Grow More in Less Space!.
Amongst all the Ferns grown at the present time, this species seems most to baffle the skill of cultivators. It is one of the scarcest of British plants, and is found at the Lake of Killarney in Ireland; hence it is commonly known by the appellation of the Irish Fern.
There is a considerable number of species belonging to this genus, but only four in cultivation, all exotics, except this one. They are difficult of importation, as, from their membranaceous texture, it is almost impossible to transport them to England from their native swamps and forests in a living state.
There is one species found clinging to the trees in the West Indies which corresponds with our Irish Fern, and is described by Swartz as T. radicans; another is found in TenerifFe, and is described by Willdenow as T. speciosum; hence the specific name of speciosum is adopted for our Irish plant. There is not a shadow of doubt that all who grow this truly elegant plant feel anxious that it should thrive with them; but the reason why it is so often seen in an unhealthy state is simply because the atmosphere by which it is surrounded is not congenial to the development of its proper functions.
Let us take a lesson from the book of Nature, and we shall find that the proper habitation of this plant is a wet dripping rock, screened from the sun and wind, and an atmosphere always loaded with moisture. From thence we may justly infer, that it would be impossible to cultivate this plant in a dry spot, where the sun and wind have much influence; hence, although it is found in cultivation amongst most collections of British Ferns, it is mostly, with one or two exceptions, in a small and miserable condition.
About five years ago, a plant was received at the Royal Botanic Gardens, Kew, from the late Mr. Cameron of Birmingham, which had then three small fronds upon it; it was potted in a 4-inch pot filled with broken potsherds and a few pieces of peat. Some time after, two other specimens were sent to Kew direct from Killarney, under the names of T. speciosum and the variety Andrewsii. They were treated similarly to the preceding one, and both placed under a glass case, in the interior of which was formed a little stone-work with broken bricks and stones. They continued to grow until the rhizoma reached the outside of the pot; the roots then began to adhere to the outside, and the plants grew more vigorously than ever; the rhizoma began to ramify, and are at this time (November, 1849), if extended in a straight line, many feet long. The one plant in the 4-inch pot has more than sixty fronds upon it, and the other thirty-five; they seem perfectly at home, and are growing with as great luxuriance as at the Lake of Killarney or in the laurel-forest of Teneriffe. The case is placed within a pit having a western aspect, where it is screened from the sun on the south and east sides, - the wind never reaches it, and the atmosphere is kept constantly loaded with moisture.
By this means it is always cool in summer, and never so low as the freezing-point in winter. The accompanying plate represents one of the fronds and rhizoma of the natural size.
Kew, November 1849. J. Houlston.