Concept

Arbuste

Résumé
A prostrate shrub is a woody plant, most of the branches of which lie upon or just above the ground, rather than being held erect as are the branches of most trees and shrubs. Prostration may occur because the supporting tissues in stems are not strong enough to support the weight of the plant, causing the plant to bend until it reaches the ground. Alternatively, it may occur because of a genetic disposition for branches to grow horizontally on or just under the ground; for example, as a strategy to avoid overly strong sunlight. Finally, environmental factors such as strong winds laden with sand or salt may tend to prune away erect branches, thereby creating a prostrate habit in plants that may not be predisposed to prostration. Prostrate shrubs are used in horticulture as groundcovers and in hanging baskets, and to bind soils and prevent erosion in remedial landscaping. They are also important components of rock gardens. The shrinking size of urban gardens has meant an increase in demand for and desirability of dwarf and prostrate forms of many garden plants. More recently, prostrate shrubs have received attention for their usefulness in planting green roofs and green walls, where they can contribute to environmental conservation. Prostrate plant forms may arise from deliberate breeding and hybridisation, such as the groundcover grevilleas, including Grevillea "Poorinda Royal Mantle", and G. "Bronze Rambler", or by selection of forms of plants growing in exposed areas. The windswept coastal heathlands and cliffs of far southeastern New South Wales have yielded Banksia 'Roller Coaster' and Banksia 'Pygmy Possum'. These are flattened varieties of less than 0.5 m in height of the species Banksia integrifolia and Banksia serrata, respectively, both of which grow to sizeable trees of 10 m (30 ft) or more in height. The origin of others is unclear; Cootamundra Wattle (Acacia baileyana) is a popular and widely used garden plant in Australia, a prostrate form of which is also in cultivation.
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