Editing Pinus flexilis (section)

== Description ==
Its pliant branches gives it the common name "limber" and specific epithet ''flexilis''. Its needles are about {{Convert|8|cm|sp=us|frac=4}} long and a dark, blueish green.<ref name=":0">{{Cite book |last1=Arno |first1=Stephen F. |url=https://www.worldcat.org/oclc/1141235469 |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=26, 43–49 |language=en |oclc=1141235469 |orig-date=1977}}</ref> Its bark is heavily creased and dark grey. Its pale wood is lightweight and soft.

''Pinus flexilis'' is typically a high-elevation pine, often marking the tree line either on its own, or with [[whitebark pine]] (''Pinus albicaulis''), either of the [[bristlecone pine]]s, or [[lodgepole pine]] (''Pinus contorta''). In favorable conditions, it makes a tree to {{convert|20|m|ft|round=5|abbr=off}}, rarely {{convert|25|m|ft|round=5|abbr=on}} tall. On exposed tree line sites, mature trees are much smaller, reaching heights of only {{convert|5|-|10|m|ft|round=5|abbr=on|sp=us}}.<ref name="Moore2008">{{cite book |last1=Moore |first1=Gerry |title=National Wildlife Federation Field Guide to Trees of North America |last2=Kershner |first2=Bruce |last3=Tufts |first3=Craig |last4=Mathews |first4=Daniel |last5=Nelson |first5=Gil |last6=Spellenberg |first6=Richard |last7=Thieret |first7=John W. |last8=Purinton |first8=Terry |last9=Block |first9=Andrew |publisher=Sterling |year=2008 |isbn=978-1-4027-3875-3 |location=New York |page=81 |display-authors=4}}</ref>  In steeply-sloping, rocky, and windswept terrain in the Rocky Mountains of southern Alberta, limber pine is even more stunted, occurring in old stands where mature trees are consistently less than {{convert|3|m|ft|0|abbr=on}} in height.<ref>{{cite journal|last1=Letts|first1=M.G.|first2=K.N.|last2=Nakonechny|first3=K.E.|last3=Van Gaalen|first4=C.M.|last4=Smith|year=2009|url=http://people.uleth.ca/~matthew.letts/Letts%20et%20al%202009%20CJFR.pdf|title=Physiological acclimation of ''Pinus flexilis'' to drought stress on contrasting slope aspects in Waterton Lakes National Park, Alberta, Canada|journal=Canadian Journal of Forest Research|volume=39|issue=3|pages=629–641|doi=10.1139/X08-206|bibcode=2009CaJFR..39..629L |url-status=dead|archive-url=https://web.archive.org/web/20110716093742/http://people.uleth.ca/~matthew.letts/Letts%20et%20al%202009%20CJFR.pdf|archive-date=2011-07-16}}</ref>

One of the world's oldest living limber pine trees grows on the banks of the upper North Saskatchewan River at Whirlpool Point in Alberta.
Recent measurements give a maximum girth of 185". In 1986, a core sample 10&nbsp;cm was retrieved by two researchers who counted 400 rings.
Extrapolating this data gives an age close to 3,000 years.

{{gallery|mode=packed
|File:Pinus flexilis male cones.jpg|Male cones of a limber pine, eastern [[Sierra Nevada (U.S.)|Sierra Nevada]], California
|File:Limberpinecone.jpg|Limber pine cone from [[San Jacinto Mountains]]
}}

=== Similar species ===
''Pinus flexilis'' is a member of the [[Pinus classification|white pine]] group, ''[[Pinus]]'' subgenus ''[[Strobus]]'', and like all members of that group, the leaves ('needles') are in [[fascicle (botany)|fascicles]] (bundles) of five,<ref name=":0" /> with a deciduous sheath. This distinguishes it from the [[lodgepole pine]], with two needles per fascicle, and the bristlecone pines, which share five needles per fascicle but have a semi-persistent sheath.

==== ''Pinus albicaulis'' ====
Distinguishing limber pine from the related whitebark pine (''P. albicaulis''), also a white pine, is very much more difficult, and can only easily be done by the cones. In limber pine, the cones are {{convert|6-15|cm|in|frac=4|abbr=on}} long<ref name=":0" /> where the species overlap, green when immature, and open to release the seeds; the scales are not fragile. In whitebark pine, the cones are {{convert|4|-|7|cm|in|frac=4|abbr=on}} long, dark purple when immature, and do not open on drying, but are fragile and are pulled apart by birds to release the seeds.<ref>{{cite web |title=''Pinus'' subgenus ''Strobus'' |url=http://www.pinetum.org/cones/PNStrobus.htm |work=Michael P. Frank's Cone Collection |publisher=Arboretum de Villardebelle}}</ref> A useful clue is that whitebark pines almost never have intact old cones lying under them, whereas limber pines usually do.
<ref>{{cite web |last1=Roady |first1=Laura |title=Whitebark Pine |url=http://fwp.mt.gov/mtoutdoors/HTML/articles/portraits/whitebarkpine.htm |access-date=15 March 2015 |website=Montana Outdoors |publisher=Montana Fish, Wildlife & Parks}}</ref>

==== ''Pinus monticola'' ====
In the absence of cones, limber pine can also be hard to tell from [[Western white pine]] (''P. monticola'') where they occur together in the northern Rockies and the Sierra Nevada east slope. The most useful clue here is that limber pine needles are entire (smooth when rubbed gently in both directions), whereas Western white pine needles are finely serrated (feeling rough when rubbed gently from tip to base). Limber pine needles are also usually shorter, {{convert|4|-|7|cm|in|frac=4|abbr=on}} long, while western white pine needles are {{convert|5|-|10|cm|in|0|abbr=on}}, though the ranges overlap.