Alpines or alpine plants are usually low growing specimens, which have the uncanny ability to thrive in tough surroundings, comparable to their origins atop the Alps, Himalayas and Andes. An alpine is the common name given to any plant found on the slopes of mountains such as these, at a height above which trees fail to grow. As water can be limited where they grow in the wild, quite a few alpines have taken on a low cushion form, while others have fleshy or hairy leaves to prevent excessive water loss, leading to the plant drying out. Most alpines can also withstand low temperatures and cold winds, but have a strong dislike of excessive rain.
Sunny mountain flowers.Many alpines produce brightly coloured flowers because in alpine areas pollinating insects can be scarce; the strikingly bright alpine flowers are one sure way of attracting these winged pollinators from miles around. To my eye, a massed bedding display or a host of naturalised bulbs are the only equals to the colours displayed by an alpine filled rockery. To enable brilliant alpine blooming, the industrious gardener should do his/her best to offer the plants a free draining growing position. We are aiming as best we can to recreate the situation where alpines occur in the wild, a sunny mountain slope with a gritty free draining soil.
How to create your drainage layer.The advance creation of a drainage layer beneath the rockery will provide free drainage for the many alpine plants that require such conditions. A typical fast drainage layer beneath an alpine garden requires you to excavate down to a depth of 20 cm. Back fill the area with a 10 cm layer of rubble or large broken stone, followed by a 5 cm layer of rough gravel or chip. This gravel need not be the fancy decorative sort, as it will be buried out of sight, so something like the chip that is used by road workers to fill potholes will suffice. Then, cover this gravel with a layer of weed prevention fabric such "Plantex" or "Mypex" to prevent soil washing down and filling (blocking) the drainage cavities. Finally, spread another 5 cm layer of rough gravel or chip on top, this sandwich's the fabric and fills the 20 cm excavation right to the top.
This advance creation of drainage beneath the rockery is a very important step in its construction especially if your local soil is on the sticky side.
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