Editing Willow (section)

==Ecology==
[[File:Bourgoyen knotted willow and woodpile.jpg|thumb|upright|[[Pollarding|Pollard willow]] and woodpile in the [[Bourgoyen-Ossemeersen]], [[Ghent]], Belgium]]
[[File:Kopfweiden 1.jpg|thumb|[[Berlin]] [[Britzer Garten]] [[Pollarding|pollarded]] willow tree in the spring of March 2018]]

Willows are [[shade tolerant]] and typically short-lived. They require disturbances to outcompete conifers or large deciduous species. The seeds are tiny, plentiful, carried by wind and water, and viable only for a few days; they require warm and moist conditions to take root. The plants can also [[reproduce vegetatively]] from decapitated stumps and branches.<ref name="Arno-2020">{{Cite book |last1=Arno |first1=Stephen F. |url=https://books.google.com/books?id=qDD4DwAAQBAJ |title=Northwest Trees: Identifying & Understanding the Region's Native Trees |last2=Hammerly |first2=Ramona P. |publisher=[[Mountaineers Books]] |year=2020 |isbn=978-1-68051-329-5 |edition=field guide |location=Seattle |pages=193–196 |language=en |oclc=1141235469 |orig-date=1977}}</ref>

Willows produce a modest amount of [[nectar]] from which bees can make [[honey]], and are especially valued as a source of early pollen for bees.<ref name="Hageneder-2001" /> Various animals browse the foliage<ref name="Angier-1974" /> or shelter amongst the plants. Beavers use willows to build dams.<ref name="Arno-2020" /> The trees are used as food by the [[larva]]e of some species of [[Lepidoptera]], such as the [[Nymphalis antiopa|mourning cloak butterfly]].<ref>"Mourning Cloak". Study of Northern Virginia Ecology. Fairfax County Public Schools.</ref> Ants, such as [[Formica rufa group|wood ants]], are common on willows inhabited by [[aphid]]s, coming to collect aphid [[Honeydew (secretion)|honeydew]], as sometimes do [[wasp]]s.

===Pests and diseases===
Willow species are hosts to more than a hundred aphid species, belonging to ''Chaitophorus'' and other genera,<ref>{{cite book|title=Aphids on the World's Trees|author1=Blackman, R. L.|author2=Eastop, V. F.|year=1994|publisher=CABI|isbn=9780851988771|url=http://www.aphidsonworldsplants.info/w_HOSTS_S.htm#Salix}}{{Dead link|date=August 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> forming large colonies to feed on plant juices, on the underside of leaves in particular.<ref>{{cite book|title=Pests of Ornamental Trees, Shrubs and Flowers|author=David V. Alford|year=2012|pages=78|publisher=Manson Publishing Limited |url=https://books.google.com/books?id=AUqYrRc8-AcC&pg=PA78|archive-url=https://web.archive.org/web/20130604015345/http://books.google.com/books?id=AUqYrRc8-AcC&pg=PA78|url-status=dead|archive-date=4 June 2013|isbn=9781840761627}}</ref> ''[[Corythucha elegans]]'', the willow lace bug, is a bug species in the family [[Tingidae]] found on willows in North America. ''[[Rhabdophaga rosaria]]'' is a type of gall found on willows.

[[Rust (fungus)|Rust]], caused by fungi of genus ''[[Melampsora]]'', is known to damage leaves of willows, covering them with orange spots.<ref>{{cite web|url=http://plantclinic.cornell.edu/factsheets/willowleafrust.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://plantclinic.cornell.edu/factsheets/willowleafrust.pdf |archive-date=2022-10-09 |url-status=live |title=Leaf Rust |author=Kenaley, Shawn C.|year=2010 |display-authors=etal}}</ref>

=== Conservation ===
Some [[Indigenous peoples of the Americas|Native Americans]] allowed [[Fire ecology|wildfires to burn]] and set fires intentionally, allowing new stands to form.<ref name="Arno-2020" />

A small number of willow species were widely planted in Australia, notably as [[erosion]]-control measures along watercourses. They are now regarded as invasive weeds which occupy extensive areas across southern Australia and are considered 'Weeds of National Significance'. Many catchment management authorities are removing and replacing them with native trees.<ref>{{cite web |url=http://www.dse.vic.gov.au/dpi/nreninf.nsf/childdocs/-1C62D26CD3AF6FE44A2568B300051289-8E21A59E53B35BEFCA256BC80005C14F-E1EB709D7DCE1BC9CA256F070003E8D8-FAC3FFA202EA6384CA256BCF000AD522?open |title=Willows along watercourses: managing, removing and replacing |author=Albury/Wodonga Willow Management Working Group |date=December 1998 |publisher=Department of Primary Industries, State Government of Victoria}}</ref><ref>{{cite web |url=http://www.hoadley.net/cremer/willows/docs/WillowInBiodiversity.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.hoadley.net/cremer/willows/docs/WillowInBiodiversity.pdf |archive-date=2022-10-09 |url-status=live |title=Introduced willows can become invasive pests in Australia |first=Kurt W. |last=Cremer |year=2003 }}</ref>