Pests of Rock Plants
Alpine and rock plants are no different from ordinary garden plants in the range of pests to which they are prone. A few samples of these pests are given below (in order by degree of horridness).
For some reason, birds find great sport in shredding cushion and mat- forming alpines and their favourite seasons for this seem to be spring and early autumn. Some people swear by black thread spun like a web across the rock garden; others use various bird-scaring devices. I have even seen one garden where each plant was given a protective helmet of chicken wire, which turned the garden into a weird sculpture park. Since there are only two seasons of main destruction, I suggest bird scaring tape, also known as humming tape. A few lengths of this stretched across the garden is no more obtrusive than any other device, yet is easier to install and remove. It also interferes less with your view of any ground-hugging plants you may have planted, since the tape must be at least 90-120 cm/3-4 ft above the ground. It does work.
SLUGS AND SNAILS
If you already garden, you will no doubt have developed your own line of defence against these creatures. Most people’s chosen method usually involves a liberal scattering of slug pellets. Slug pellets are very effective but are also unsightly and can be dangerous to pets and small children if not used with care. Generally though, if theis sandy enough to provide perfect and the grit around the plants sharp enough, this will deter slugs and snails to some extent since they do not like to slither across gritty places — it is very uncomfortable.
APHIDS OR GREENFLIES
These are common, against which there are a whole range of sprays and powders. Good garden hygiene helps to prevent infestations of these pests, so try to keep your rock garden clean of debris. Systemic sprays are especially effective, taken into the plant’s system through the leaves, it kills the aphids as they suck the sap. In a alpine house you will have to fumigate, especially if many of the plants are hairy or tufted.
These are generally most troublesome with bulbs and conns. I once planted several handfuls of crocus species, some in the ground and some in pans and not one came up. The mice had taken the lot. Mousetraps can be used in both frames and alpine houses, but, unfortunately, I have yet to find a solution for the garden.
RED SPIDER MITES
These pests thrive in the dry, warm conditions of alpine houses, but if you keep your alpine house well-ventilated and spray to raise the humidity during summer, you should avoid infestations. Similarly, if the garden becomes overheated and dry hose it down, setting the spray to a fine mist.