Editing Evergreen

{{short description|Plant that has leaves in all seasons}}
{{About|the type of plant}}
[[File:Abies alba 02.jpg|right|300px|thumb|A [[Abies alba|silver fir]] shoot showing three successive years of retained leaves.]]
[[File:2018-06-01 (123) Spiraea (spiraea) at Bichlhäusl in Frankenfels, Austria.jpg|thumb|304x304px|Evergreen ]]
In [[botany]], an '''evergreen''' is a plant which has [[Leaf|foliage]] that remains green and functional throughout the year.<ref>{{Cite web |date=2023-01-23 |title=Evergreen |url=https://mgnv.org/plants/glossary/evergreen/ |access-date=2024-06-07 |website=Master Gardeners of Northern Virginia |language=en-US}}</ref> This contrasts with [[deciduous]] plants, which lose their foliage completely during the winter or dry season. Consisting of many different species, the unique feature of evergreen plants lends itself to various environments and purposes.

==Evergreen species==
{{cite section|date=December 2022}}
There are many different kinds of evergreen plants, including [[tree]]s, [[shrub]]s, and vines.{{cn|date=June 2024}} Evergreens include:
* Most species of [[conifer]]s (e.g., [[pine]], [[Tsuga|hemlock]], [[spruce]], and [[fir]]), but not all (e.g., [[larch]]).<ref>{{Cite web |last=Rose |first=Nancy |date=2016-01-06 |title=Not All Conifers are Evergreen |url=https://arboretum.harvard.edu/stories/not-all-conifers-are-evergreen/ |access-date=2024-06-07 |website=Arnold Arboretum |publisher=Harvard University |language=en-us}}</ref>
* [[Live oak]], [[holly]], and "ancient" [[gymnosperm]]s such as [[cycad]]s
* Many [[woody plants]] from frost-free climates
* [[Rainforest]] trees
* All [[eucalypt]]s
* [[Lycopodiopsida|Clubmosses and relatives]]
* Most [[bamboo]]s

The Latin binomial term {{Wikt-lang|la|sempervirens}}, meaning "always green", refers to the evergreen nature of the plant, for instance:
:''[[Cupressus sempervirens]]'' (a cypress)
:''[[Lonicera sempervirens]]'' (a honeysuckle)
:''[[Sequoia sempervirens]]'' (a sequoia)

The longevity of individual leaves in evergreen plants varies from a few months to several decades (over 30 years in the [[Pinus longaeva|Great Basin bristlecone pine]]<ref>Ewers, F. W. & Schmid, R. (1981). "Longevity of needle fascicles of ''Pinus longaeva'' (Bristlecone Pine) and other North American pines". ''[[Oecologia]]'' 51: 107–115</ref>).

=== Prominent evergreen families ===
{| class="wikitable"
|-
! Family name !! Example
|-
| [[Araucariaceae]] || [[Agathis australis|Kauri]]
|-
| [[Cupressaceae]] || [[Sequoia sempervirens|Sequoia]]
|-
| [[Pinaceae]] || [[Pine]]
|-
| [[Podocarpaceae]] || [[Podocarpus latifolius|Real yellowwood]]
|-
| [[Taxaceae]] || [[Taxus baccata|Yew]]
|-
| [[Cyatheaceae]] || [[Cyathea cooperi|Australian tree fern]]
|-
| [[Aquifoliaceae]] || [[Ilex aquifolium|Holly]]
|-
| [[Fagaceae]] || [[Live oak]]
|-
| [[Rutaceae]] || [[Citrus]]
|-
| [[Apocynaceae]] || [[Nerium|Oleander]]
|-
| [[Ericaceae]] || [[Rhododendron]]
|-
| [[Oleaceae]] || [[Olive]]
|-
| [[Myrtaceae]] || [[Eucalyptus]]
|-
| [[Arecaceae]] || [[Coconut]]
|-
| [[Lauraceae]] || [[Laurus nobilis|Bay]]
|-
| [[Magnoliaceae]] || [[Magnolia grandiflora|Southern magnolia]]
|-
| [[Cycadaceae]] || [[Cycas rumphii|Queen sago]]
|}

[[Sciadopitys|Japanese umbrella pine]] is unique in that it has its own family of which it is the only species.

== Differences between evergreen and deciduous species ==
Evergreen and deciduous species vary in a range of morphological and physiological characters. Generally, broad-leaved evergreen species have thicker leaves than deciduous species, with a larger volume of [[Ground tissue|parenchyma]] and air spaces per unit leaf area.<ref>{{Cite journal |last=Villar |first=Rafael |last2=Ruiz-Robleto |first2=Jeannete |last3=Ubera |first3=José Luis |last4=Poorter |first4=Hendrik |date=October 2013 |title=Exploring variation in leaf mass per area (LMA) from leaf to cell: An anatomical analysis of 26 woody species |journal=American Journal of Botany |volume=100 |issue=10 |pages=1969–1980 |doi=10.3732/ajb.1200562 |pmid=24107583}}</ref> They have larger leaf biomass per unit leaf area, and hence a lower [[specific leaf area]]. Construction costs do not differ between the groups.{{citation needed|date=February 2023}} Evergreens have generally a larger fraction of total plant biomass present as leaves (LMF),<ref>{{Cite journal |last=Poorter |first=Hendrik |last2=Jagodzinski |first2=Andrzej M. |last3=Ruiz-Peinado |first3=Ricardo |last4=Kuyah |first4=Shem |last5=Luo |first5=Yunjian |last6=Oleksyn |first6=Jacek |last7=Usoltsev |first7=Vladimir A. |last8=Buckley |first8=Thomas N. |last9=Reich |first9=Peter B. |last10=Sack |first10=Lawren |date=2015 |title=How does biomass distribution change with size and differ among species? An analysis for 1200 plant species from five continents |journal=New Phytologist |volume=208 |issue=3 |pages=736–749 |bibcode=2015NewPh.208..736P |doi=10.1111/nph.13571 |pmc=5034769 |pmid=26197869}}</ref> but they often have a lower rate of photosynthesis.

==Reasons for being evergreen or deciduous==
{{Refimprovesect|date=August 2023}}
[[Image:Live oak Georgetown.jpg|right|thumb|A [[Quercus virginiana|southern live oak]] in [[South Carolina]] during winter]]
[[File:Ecuadorian Amazon rain forest, looking toward the Andes.jpg|thumb|[[Oriente (Ecuador)|Ecuadorian Amazon]] rainforest. This humid tropical forest has warm temperatures and receives rainfall year round. Vegetation consists of a majority of broadleaf evergreen species.<ref>{{Cite web |last=Woodward |first=Dr. Susan L. |title=Amazon Rainforest |url=https://php.radford.edu/~swoodwar/biomes/?page_id=2052 |access-date=2024-11-16 |website=Department of Geospatial Science, Radford University}}</ref>]]

Deciduous trees shed their leaves usually as an adaptation to a cold or dry/wet season. Evergreen trees also lose leaves, but each tree loses its leaves gradually and not all at once. Most [[tropical rainforest]] plants are considered to be evergreens, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous. Most warm [[temperate climate]] plants are also evergreen.{{Citation needed|date=February 2023}} In cool temperate climates, fewer plants are evergreen. In such climates, there is a predominance of [[conifers]] because few evergreen [[flowering plant|broadleaf]] plants can [[Psychrophile|tolerate severe cold]] below about {{convert|-26|C|F}}.{{Clarify|reason=check stated temperature|date=February 2023}}{{Citation needed|date=February 2023}} In addition, evergreen foliage experiences significant leaf damage in these cold, dry climates. Root systems are the most vulnerable aspect of many plants. Even though roots are insulated by soil, which tends to be warmer than average air temperatures, soil temperatures that drop too low can kill the plant. The exact temperature which evergreen roots can handle depends on the species, for example, ''[[Picea glauca]]'' (White Spruce) roots are killed at {{cvt|-10|F}}.<ref name="Niemiera-2023">{{Cite book |last=Niemiera |first=Alex X. |url=https://pressbooks.lib.vt.edu/emgtraining/chapter/13/ |title=Virginia Cooperative Extension Gardener Handbook |date=2023-03-13 |language=en |chapter=Chapter 13: Woody Landscape Plants}}</ref>

In areas where there is a reason for being deciduous, e.g. a cold season or dry season, evergreen plants are usually an adaptation of low nutrient levels. Additionally, they usually have [[Sclerophyll|hard leaves]] and have an excellent water economy due to scarce resources in the area in which they reside.<ref name="Álvarez-Yépiz-2017">{{Cite journal |last=Álvarez-Yépiz |first=Juan C. |last2=Búrquez |first2=Alberto |last3=Martínez-Yrízar |first3=Angelina |last4=Teece |first4=Mark |last5=Yépez |first5=Enrico A. |last6=Dovciak |first6=Martin |date=2017-02-01 |title=Resource partitioning by evergreen and deciduous species in a tropical dry forest |url=https://doi.org/10.1007/s00442-016-3790-3 |url-status=live |journal=Oecologia |language=en |volume=183 |issue=2 |pages=607–618 |bibcode=2017Oecol.183..607A |doi=10.1007/s00442-016-3790-3 |issn=1432-1939 |pmid=27915413 |s2cid=3798020 |archive-url=https://web.archive.org/web/20220913050311/https://link.springer.com/article/10.1007/s00442-016-3790-3 |archive-date=2022-09-13 |access-date=2021-02-16}}</ref> The excellent water economy within the evergreen species is due to high abundance when compared to deciduous species,<ref name="Álvarez-Yépiz-2017" /> whereas deciduous trees lose nutrients whenever they lose their leaves. In warmer areas, species such as some [[pine]]s and [[Cupressaceae|cypresses]] grow on poor soils and [[disturbed ground]].{{Fact|date=August 2023}} In ''[[Rhododendron]]'', a genus with many broadleaf evergreens, several species grow in mature forests but are usually found on highly acidic soil where the nutrients are less available to plants.{{Fact|date=August 2023}} In [[taiga]] or [[boreal forest]]s, it is too cold for the [[Soil organic matter|organic matter in the soil]] to decay rapidly, so the nutrients in the soil are less easily available to plants, thus favoring evergreens.{{Fact|date=August 2023}}

In temperate climates, evergreens can reinforce their own survival; evergreen leaf and needle litter has a higher carbon–nitrogen ratio than deciduous [[leaf litter]], contributing to a higher soil acidity and lower soil nitrogen content. This is the case with Mediterranean evergreen seedlings, which have unique C and N storages that allow stored resources to determine fast growth within the species, limiting competition and bolstering survival.<ref>{{Cite journal |last=Uscola |first=Mercedes |last2=Villar-Salvador |first2=Pedro |last3=Gross |first3=Patrick |last4=Maillard |first4=Pascale |date=2015-05-01 |title=Fast growth involves high dependence on stored resources in seedlings of Mediterranean evergreen trees |journal=Annals of Botany |language=en |volume=115 |issue=6 |pages=1001–1013 |doi=10.1093/aob/mcv019 |issn=0305-7364 |pmc=4407060 |pmid=25817313 |doi-access=free}}</ref> These conditions favor the growth of more evergreens and make it more difficult for deciduous plants to persist. In addition, the shelter provided by existing evergreen plants can make it easier for younger evergreen plants to survive cold and/or drought.<ref>Aerts, R. (1995). [http://www.falw.vu.nl/nl/Images/Aerts1995_tcm19-94783.pdf "The advantages of being evergreen"]; {{Webarchive|url=https://web.archive.org/web/20150924010354/http://www.falw.vu.nl/nl/Images/Aerts1995_tcm19-94783.pdf |date=2015-09-24 }}. ''Trends in Ecology & Evolution'' 10 (10): 402–407.</ref><ref>Matyssek, R. (1986) "Carbon, water and nitrogen relations in evergreen and deciduous conifers". ''Tree Physiology'' 2: 177–187.</ref><ref>Sobrado, M. A. (1991) "Cost-Benefit Relationships in Deciduous and Evergreen Leaves of Tropical Dry Forest Species". ''Functional Ecology'' 5 (5): 608–616.</ref>

== Uses ==
Evergreen plants can have decorative as well as functional uses. In months where most other plants are dormant, evergreens with their sturdy structure, and vibrant foliage are popular choices to beautify a landscape. Additionally, evergreens can serve as a [[windbreak]], stopping heat loss from buildings during cold months when placed on the northwest side of a structure.<ref name="Niemiera-2023" />

==See also==
{{portal|Plants|Trees|Botany
}}
* [[Semi-deciduous]] (semi-evergreen)

==References==
{{reflist}}

==External links==
* {{Cite Americana|wstitle=Evergreens|author=Helen Ingersoll |short=x}}

[[Category:Plants]]
[[Category:Botany]]
[[Category:Trees]]