Shrub

Summary

A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple stems and shorter height, less than 6–10 m (20–33 ft) tall.[1][2] Small shrubs, less than 2 m (6.6 ft) tall are sometimes termed as subshrubs. Many botanical groups have species that are shrubs, and others that are trees and herbaceous plants instead.

A broom shrub in flower

Some definitions state that a shrub is less than 6 m (20 ft) and a tree is over 6 m. Others use 10 m (33 ft) as the cut-off point for classification.[2] Many species of tree may not reach this mature height because of hostile less than ideal growing conditions, and resemble a shrub-sized plant. However, such species have the potential to grow taller under the ideal growing conditions for that plant. In terms of longevity, most shrubs fit in a class between perennials and trees; some may only last about five years even in good conditions, others, usually the larger and more woody ones, may live to 70 or more, but on average they last 7–10 years.[3]

Shrubland is the natural landscape dominated by various shrubs; there are many distinct types around the world, including fynbos, maquis, shrub-steppe, shrub swamp and moorland. In gardens and parks, an area largely dedicated to shrubs (now somewhat less fashionable than a century ago) is called a shrubbery, shrub border or shrub garden. There are many garden cultivars of shrubs, bred for flowering, for example rhododendrons, and sometimes even leaf colour or shape.

Compared to trees and herbaceous plants, perhaps a relatively small number of shrubs have agricultural or commercial uses. Apart from the several berry-bearing species (using the culinary rather than botanical definition), few are eaten directly, and they are generally too small for much timber use unlike trees.[4] Those that are used include several perfumed species such as lavender and rose, and a wide range of plants with medicinal uses. Tea and coffee are on the tree-shrub boundary;[5] they are normally harvested from shrub-sized plants, but these would be large enough to become small trees if left to grow instead.

DefinitionEdit

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]

Use in gardens and parksEdit

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]

Botanical structureEdit

 
Shrub vegetation (with some cactus) in Webb County, Texas.
 
Blackthorn shrub (Prunus spinosa) in the Vogelsberg
 
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

List of shrubsEdit

Those marked with * can also develop into tree form if in ideal conditions.

A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
  • Ulex (Gorse)
  • Ulmus pumila celer (Turkestan elm – Wonder Hedge)
  • Ungnadia (Mexican Buckeye)
V
W
X
Y
Z

ReferencesEdit

  1. ^ Lawrence, Anna; Hawthorne, William (2006). Plant Identification: Creating User-friendly Field Guides for Biodiversity Management. Routledge. pp. 138–. ISBN 978-1-84407-079-4.
  2. ^ a b c d e f Allaby, Michael (2019). A dictionary of plant sciences. Oxford Oxford University Press. ISBN 9780198833338. OCLC 1097073225.
  3. ^ "Life Spans of Small Trees and Shrubs". McCabe's Landscape Construction. 2014-02-27. Retrieved 2022-04-29.
  4. ^ Rosewood does not come from roses.
  5. ^ Clayton, Liz. "Is The Coffee Plant A Tree, Bush, Or Shrub?". sprudge.com. Retrieved 2022-04-29.
  6. ^ Bremness, Lesley (1994). The complete book of herbs. Viking Studio Books. p. 8. ISBN 9780140238020.
  7. ^ Fischer, Peggy (1990). Essential shrubs: the 100 best for design and cultivation. Friedman/Fairfax Publishers. pp. 9–. ISBN 978-1-56799-319-6. ... Examples of subshrubs include candytuft, lavender, and rosemary. These broad definitions are ...
  8. ^ "What is a Subshrub?". World of Flowering Plants. 2017-05-15. Retrieved 2022-04-29.
  9. ^ Whitefield, Patrick (2002). How to Make a Forest Garden. Permanent Publications. pp. 113–. ISBN 978-1-85623-008-7.
  10. ^ Varkulevicius, Jane (17 May 2010). Pruning for Flowers and Fruit. Csiro Publishing. ISBN 9780643101975. Retrieved 19 December 2017 – via Google Books.
  11. ^ "Rejuvenation or Renewal Pruning to Restore Overgrown Shrubs". Organic Plant Care LLC | Organic Lawn & Plant Health Service in Hunterdon, Morris, Somerset & Union Counties, NJ and Bucks County, PA. 2019-02-21. Retrieved 2022-04-29.
  12. ^ Turpin, Jason (2018-08-29). "What is Selective Tree and Shrub Pruning-How to Prune Correctly!". Turpin Landscape Design/Build. Retrieved 2022-04-29.
  13. ^ Elliott, Franklin Reuben (1 November 2008). Popular Deciduous and Evergreen Trees and Shrubs. Applewood Books. ISBN 9781429012904. Retrieved 19 December 2017 – via Google Books.
  14. ^ Costermans, L. F. (1993) Native trees and shrubs of South-Eastern Australia. rev. ed. ISBN 0-947116-76-1