Shrub
Shrub
A shrub or bush is a small- to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. They are distinguished from trees by their multiple stems and shorter height, less than 6 m-10 m (20 ft–33 ft) tall.[1][2] Small shrubs, less than 2 m (6.6 ft) tall are sometimes termed subshrubs.[3]
Definition
Shrubs are perennial woody plants, and therefore have persistent woody stems above ground (compare with 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.[4]
Height
Some definitions state that a shrub is less than 6 m and tree is over 6 m. Others use 10 m as the cut off point.[2] Many species of tree may not reach this mature height because of 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.
Multiple stems
Most definitions characterize shrubs as possessing multiple stems with no main trunk.[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.
Many trees can grow in multiple stemmed forms also, such as oak or ash.[2]
Use in parks
An area of cultivated shrubs in a park or a garden is known as a shrubbery.[5] When clipped as topiary, suitable species or varieties of shrubs develop dense foliage and many small leafy branches growing close together.[6] Many shrubs respond well to renewal pruning, in which hard cutting back to a "stool" results in long new stems known as "canes". 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.[7]
Botanical structure
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.[8]
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%) — 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 shrubs (bushes)
Those marked with * can also develop into tree form.
- A
Abelia
Acer
Actinidia
Aloe
Aralia (Angelica Tree, Hercules' Club) *
Arctostaphylos (Bearberry, Manzanita) *
Aronia
Artemisia (Sagebrush)
Aucuba
- B
Berberis
Bougainvillea
Brugmansia
Buddleja
Buxus
- C
Calia
Callicarpa
Callistemon
Calluna
Calycanthus
Camellia (Camellia, Tea) *
Caragana
Carpenteria
Caryopteris
Cassiope
Ceanothus
Celastrus
Ceratostigma
Cercocarpus
Chaenomeles
Chamaebatiaria
Chamaedaphne
Chimonanthus
Chionanthus
Choisya
Cistus
Clerodendrum
Clethra
Clianthus
Colletia
Colutea
Comptonia
Cornus
Corylopsis
Cotinus
Cotoneaster
Cowania (Cliffrose)
Crataegus
Crinodendron
Cytisus and allied genera (Broom) *
- D
Daboecia (Heath)
Danae
Daphne
Decaisnea
Dasiphora
Dendromecon
Desfontainea
Deutzia
Diervilla
Dipelta
Dirca
Dracaena
Drimys (Winter's Bark) *
Dryas
- E
Edgeworthia
Elaeagnus (Elaeagnus) *
Embothrium (Chilean Firebush) *
Empetrum (Crowberry)
Enkianthus
Ephedra
Epigaea (Trailing Arbutus)
Erica (Heath)
Eriobotrya
Escallonia
Eucryphia
Euonymus
Exochorda
- F
Fabiana
Fallugia
Fatsia
Forsythia
Fothergilla
Franklinia
Fremontodendron
Fuchsia
- G
Garrya
Gaultheria (Salal)
Gaylussacia (Huckleberry)
Genista (Broom) *
Gordonia (Loblolly-bay) *
Grevillea
Griselinia
- H
Hakea
Halesia (Silverbell) *
Halimium
Hamamelis
Hebe
Hedera
Helianthemum
Hibiscus
Hippophae
Hoheria
Holodiscus (Creambush)
Hudsonia
Hydrangea
Hypericum (Rose of Sharon)
Hyssopus
- I
Ilex (Holly) *
Illicium (Star Anise) *
Indigofera
Itea (Sweetspire)
- J
Jamesia
Jasminum
Juniperus
- K
Kalmia
Kerria
Kolkwitzia (Beauty-bush)
- L
Lagerstroemia
Lapageria
Lantana
Lavandula
Lavatera
Ledum
Leitneria
Lespedeza
Leptospermum
Leucothoe
Leycesteria
Ligustrum
Lindera
Linnaea
Lonicera
Lupinus
Lycium
- M
Magnolia
Mahonia
Malpighia (Acerola)
Menispermum
Menziesia
Mespilus (Medlar) *
Microcachrys
Myrica
Myricaria (Myricaria)
Myrtus
- N
Neillia
Nerium
- O
Olearia
Osmanthus
- P
Pachysandra
Paeonia
Perovskia (Russian Sage)
Persoonia
Philadelphus
Phlomis (Jerusalem Sage)
Photinia
Physocarpus
Pieris
Pistacia (Pistachio, Mastic) *
Pittosporum
Plumbago
Polygala
Poncirus
Prunus
Purshia (Antelope Bush)
Pyracantha
- Q
Quassia
Quercus
Quillaja (Quillay)
Quintinia (Tawheowheo) *
- R
Rhamnus
Rhododendron (Rhododendron, Azalea) *
Rhus
Ribes
Romneya
Rosmarinus (Rosemary)
Rubus (Bramble)
Ruta (Rue)
- S
Sabia *
Salix (Willow) *
Salvia
Sambucus
Santolina
Sapindus
Senecio
Simmondsia
Skimmia
Smilax
Sophora (Kowhai) *
Sorbaria
Spartium
Spiraea
Staphylea
Stephanandra
Styrax
Symphoricarpos
Syringa (Lilac) *
- T
Tamarix
Taxus
Telopea
Thuja
Thymelaea
Thymus
Trochodendron
- U
Ulex
Ulmus pumila celer (Turkestan elm – Wonder Hedge)
Ungnadia
- V
Vaccinium (Bilberry, Blueberry, Cranberry)
Verbena
Viburnum
Vinca
Viscum (Mistletoe)
- W
Weigela
- X
Xanthoceras
Xanthorhiza
Xylosma
- Y
Yucca (Yucca, Joshua tree) *
- Z
Zanthoxylum
Zauschneria
Zenobia
Ziziphus