Shrub

Shrubs are perennial woody plants, and therefore have persistent woody stems above ground (compare with succulent stems of herbaceous plants).[2] Usually, shrubs are distinguished from trees by their height and multiple stems. Some shrubs are deciduous (e.g. hawthorn) and others evergreen (e.g. holly).[2] Ancient Greek philosopher Theophrastus divided the plant world into trees, shrubs and herbs.[6]

Small, low shrubs, generally less than 2 m (6.6 ft) tall, such as lavender, periwinkle and most small garden varieties of rose, are often termed as subshrubs.[7][8]

Most definitions characterize shrubs as possessing multiple stems with no main trunk below.[2] This is because the stems have branched below ground level. There are exceptions to this, with some shrubs having main trunks, but these tend to be very short and divide into multiple stems close to ground level without a reasonable length beforehand. Many trees can grow in multiple stemmed forms also while being tall enough to be trees, such as oak or ash.[2]

An area of cultivated shrubs in a park or a garden is known as a shrubbery.[9] When clipped as topiary, suitable species or varieties of shrubs develop dense foliage and many small leafy branches growing close together.[10] Many shrubs respond well to renewal pruning, in which hard cutting back to a "stool", removes everything but vital parts of the plant, resulting in long new stems known as "canes".[11] Other shrubs respond better to selective pruning to dead or unhealthy, or otherwise unattractive parts to reveal their structure and character.[12]

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.[13]

Shrub vegetation (with some cactus) in Webb County, Texas.

Blackthorn shrub (Prunus spinosa) in the Vogelsberg

Hydrangea macrophylla

Winter-flowering Witch-hazel (Hamamelis)

Senecio angulatus, a scrambling shrub by the sea (yellow-flowered).

In botany and ecology, a shrub is more specifically used to describe the particular physical canopy structure or plant life-form of woody plants which are less than 8 metres (26 ft) high and usually multiple stems arising at or near the surface of the ground. 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.[14]

For shrubs that are 2–8 metres (6.6–26.2 ft) high, the following structural forms are categorized:

• dense foliage cover (70–100%) — closed-shrubs
• mid-dense foliage cover (30–70%) — open-shrubs
• 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 if in ideal conditions.