▁the ▁dry ads , ▁the ▁tree ▁n ym ph s ▁of ▁ancient ▁Greek ▁myth ology . ▁The ▁classification ▁of ▁D ry as ▁within ▁the ▁Ros aceae ▁has ▁been ▁unclear . ▁The ▁genus ▁was ▁formerly ▁placed ▁in ▁the ▁sub family ▁Ros o ide ae , ▁but ▁is ▁now ▁placed ▁in ▁sub family ▁D ry ado ide ae . ▁ ▁The ▁species ▁are ▁super f icial ly ▁similar ▁to ▁Ge um ▁( with ▁which ▁they ▁share ▁the ▁common ▁name ▁av ens ), ▁Pot ent illa ▁and ▁F rag aria ▁( st raw berry ). ▁However , ▁D ry as ▁are ▁distinct ▁in ▁having ▁flowers ▁with ▁eight ▁pet als ▁( rare ly ▁seven ▁or ▁up ▁to ▁ten ), ▁instead ▁of ▁the ▁five ▁pet als ▁found ▁in ▁most ▁other ▁gener a ▁in ▁the ▁Ros aceae . ▁The ▁flowers ▁are ▁ere ct ▁and ▁white ▁with ▁a ▁yellow ▁centre ▁( D ry as ▁integr ifolia , ▁D ry as ▁oct op et ala ) ▁or ▁p end ul ous ▁and ▁all - yellow ▁( D ry as ▁drum mond ii ), ▁and ▁held ▁consp ic u ously ▁above ▁the ▁small ▁plants . ▁This ▁makes ▁them ▁very ▁popular ▁in ▁ro cker ies ▁and ▁al pine ▁gard ens . ▁The ▁hy brid ▁D ry as ▁× ▁su end ermann ii , ▁with ▁cre am ▁col oured ▁flowers , ▁has ▁gained ▁the ▁Royal ▁H ort icult ural ▁Society ’ s ▁Award ▁of ▁Garden ▁Mer it . ▁ ▁D ry as ▁toler ates ▁a ▁wide ▁variety ▁of ▁un sh aded ▁habit ats ,