View source for Dryas (plant)

{{Taxobox
| color = lightgreen
| name = ''Dryas''
| image = Dryas drummondii6.jpg
| image_width = 240px
| image_caption = ''Dryas × suendermannii''
| regnum = [[Plant]]ae
| divisio = [[Magnoliophyta]]
| classis = [[Magnoliopsida]]
| ordo = [[Rosales]]
| familia = [[Rosaceae]]
| genus = '''''Dryas'''''
| genus_authority = [[Carolus Linnaeus|L.]]
| subdivision_ranks = Speciea
| subdivision = See text
}}

'''''Dryas''''' is a genus of dwarf [[perennial]] [[herbaceous]] [[plant]]s in the [[rose]] family [[Rosaceae]], native to the [[arctic-alpine|arctic and alpine]] regions of [[Europe]], [[Asia]] and [[North America]]. The genus is named after the Greek nymph [[Dryas]].

There are three [[species]] and one [[hybrid]]:
*''[[Dryas drummondii]]'' – Drummond's Avens
*''[[Dryas integrifolia]]'' – Entire-leaved Avens
*''[[Dryas octopetala]]'' – Mountain Avens
*''Dryas × suendermannii'' – ''D. drummondii'' × ''D. octopetala''

The species are superficially similar to ''[[Geum]]'', ''[[Potentilla]]'' and [[strawberry|''Fragaria'']], but are distinct in having [[flower]]s with ''eight'' petals (rarely seven or up to ten), instead of the five petals found in most other genera in the Rosaceae. The flowers are erect and white with a yellow centre (''[[Dryas integrifolia]]'', ''[[Dryas octopetala]]'') or pendulous and all-yellow (''[[Dryas drummondii]]''), and held conspicuously above the small plants. The hybrid has pale yellow flowers. This makes them very popular in [[Rock garden|rockeries]] and [[alpine garden]]s.

The classification of ''Dryas'' within the Rosaceae is presently unclear. The genus was originally placed in the subfamily [[Rosoideae]], and later in subfamily [[Dryadeae]] along with the genera ''[[Chamaebatia]]'', ''[[Purshia]]'' and ''[[Cercocarpus]]'', all four genera sharing [[root nodule]]s that host the [[nitrogen fixation|nitrogen-fixing]] [[bacterium]] ''[[Frankia]]''. However, recent genetic research indicates that Dryadeae may be paraphyletic, with ''Dryas'' not closely related to the other three genera.

==References==
*[http://www.ars-grin.gov/cgi-bin/npgs/html/splist.pl?4000 Germplasm Resources Information Network: ''Dryas'']
*Huxley, A. (1992). ''New RHS Dictionary of Gardening''. Macmillan [''D. × suendermannii''].

[[Category:Rosaceae]]
{{Rosales-stub}}