The Alpine House
A number of choice Alpines can only be grown in theof a special greenhouse.
This is not because they will not stand the cold of our climate, as in most cases they are well used to frost and snow in their native habitat. The difficulty is that our climate here is moister overhead, and rains and fogs are apt to cause “damping off.”
The Alpine House is frequently used just for the shelter of the plants white they are in bloom, or during the winter months when the weather is most troublesome. A cold frame should be used in conjunction with the Alpine House for gradual hardening or shelter during a rest period, etc. It is usual to grow the plants in pans, which during favourable summer weather are sunk outdoors in cold frames, or in the open garden. Usually these pans are sunk in ashes to their rims, partly because the ashes main- tain a uniform temperature and moistness, and partly because they prevent slugs from gaining access to the plants.
The Alpine House does not need artificial heat, but if slight heat is available, it may sometimes be acceptable in order to create a dryer atmosphere. The house must be amply ventilated above.
Top ventilation is more important than side ventilation in an Alpine House. It is also important to provide some means of shading, which is usually required for some plants during the summer months.
The pans used for Alpine plants vary according to type, but the general size is a pan from 6-9 in. in diameter, and 4 or 5 in. deep, made of the same material as flower-pots and obtained from any nursery. From 1-3 in. of broken crocks should go into the bottoms of the pans in order to ensure ample drainage.
In the case of Androsace, for instance, which is a difficult genus to flower successfully in this climate, 3 in. of drainage crocks are generally used.
Pans of tender Alpines are often stood in a tray containing water, so that the water required by the plants percolates through thefrom below. This avoids the possibility of damping the foliage, which is a frequent source of trouble.
When repotting is necessary, this is generally done about the end of the summer, and newly-potted plants are kept close in a cold frame, shaded from bright sunshine, until they have established themselves; that is, usually for about two weeks.
Alpine plants may stand in the open all summer, but, if so, they are brought under cover usually about the beginning of October. A frostproof frame is sufficient at first, but as plants come into flower they should be removed into the Alpine House.
The generalfor use in the Alpine House is made by mixing two parts fibrous loam, one part leaf-mould, and one part gritty sand. For the lime-lovers a little broken lime rubble may be added.
PESTS AND DISEASES
Thrips, red spider, mealy bugs, scale insects and wood-lice are the common pests of the Alpine House. Slugs should not be troublesome here, although they are in the open garden.
Fumigation is the best way of treating the pests under glass, but clean culture and attention to drainage, and the mixing of a porous, gritty compost, will do more than anything else to keep down fungus diseases.
The following is a list of some of the most valuable plants for cultivation in the Alpine House. In most cases the height is only from 1-6 in.