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A shrub or bush is a small- to medium-sized woody plant. Unlike herbs, shrubs have persistent woody stems above the ground. They are distinguished from trees by their multiple stems and shorter height, and are usually under 6 m (20 ft) tall. Plants of many species may grow either into shrubs or trees, depending on their growing conditions. Small, low shrubs, generally less than 2 m (6.6 ft) tall, such as lavender, periwinkle and most small garden varieties of roses, are often termed "subshrubs".
An area of cultivated shrubs in a park or a garden is known as a shrubbery. When clipped as topiary, suitable species or varieties of shrubs develop dense foliage and many small leafy branches growing close together. Many shrubs respond well to renewal pruning, in which hard cutting back to a "stool" results in long new stems known as "canes".[clarification needed] Other shrubs respond better to selective pruning to reveal their structure and character.
Shrubs in common garden practice are generally considered broad-leaved plants, though some smaller conifers such as mountain pine and common juniper are also shrubby in structure. Species that grow into a shrubby habit may be either deciduous or evergreen.
In botany and ecology, a shrub is more specifically used to describe the particular physical structural or plant life-form of woody plants which are less than 8 metres (26 ft) high and usually have many stems arising at or near the base.
For example, a descriptive system widely adopted in Australia is based on structural characteristics based on life-form, plus the height and amount of foliage cover of the tallest layer or dominant species.
For shrubs 2–8 metres (6.6–26.2 ft) high the following structural forms are categorized:
- dense foliage cover (70–100%) — closed-shrub
- mid-dense foliage cover (30–70%) — open-shrub
- sparse foliage cover (10–30%) — tall shrubland
- very sparse foliage cover (<10%) — tall open shrubland
For shrubs less than 2 metres (6.6 ft) high the following structural forms are categorized:
- dense foliage cover (70–100%) — closed-heath or closed low shrubland—(North America)
- mid-dense foliage cover (30–70%) — open-heath or mid-dense low shrubland—(North America)
- sparse foliage cover (10–30%) — low shrubland
- very sparse foliage cover (<10%) — low open shrubland
Those marked with * can also develop into tree form.
- Anna Lawrence; William Hawthorne (2006). Plant Identification: Creating User-friendly Field Guides for Biodiversity Management. Routledge. pp. 138–. ISBN 978-1-84407-079-4.
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... Examples of subshrubs include candytuft, lavender, and rosemary. These broad definitions are ...
- Patrick Whitefield (2002). How to Make a Forest Garden. Permanent Publications. pp. 113–. ISBN 978-1-85623-008-7.
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