SOME of the alpines, though porfcctly hardy, are best grown under glass, or at least flowered under glass. This is chiefly because their blooms are so easily damaged by rough weather. As, however, these alpines need no artificial heat, they are best grown in a house to themselves, not mixed with other half-hardy plants.
As a rule it is satisfactory to stand the pans or pots containing alpines in the open, or in a cold frame, for the greater part of the year. Most of them will be moved into the alpine house for the flowering period only, being wintered in cold frames, where they remain until the flowers show.
The alpine house is best constructed as a span roof structure, running north and south, but no arrangements need be made for heating. All gardening under glass is made easier if special composts are prepared, for use as required, using peat, 1 oam, lime, sand, leaf-mould, etc., in varying proportions according to the types of plants cultivated. In the alpino house the preparation of special composts is an absolute necessity, and above all the house be supplied with splintered limestone, coarse sand, granite chippings, and similar rough materials for top dressing and for mixing with the soil to make it more open.
Staging in the alpine house can be of wooden laths (toak for preference) set from an inch to an inch and a half apart. Air circulates freely through these, and this is beneficial rather than otherwise to alpines. Special pans, from 6 to 10 inches in diameter, are used for alpines such as the showy saxifrages and andro-saces, and these, and all other pots or used in the alpine house must be well supplied with crocks to ensure good drainage.