N Arctagrostis latifolia – polargrass Arctium X Arctium lappa – great burdock X Arctium minus subsp. minus – common burdock X Arctium minus subsp. nemorosum – lesser burdock X Arctium pubens – wood burdock X Arctium tomentosum – woolly burdock, tomentose burdock X Arctium × nothum (A. lappa × A. minus) – hybrid burdock Arctophila N Arctophila fulva – pendant grass Arctostaphylos N Arctostaphylos alpina – alpine bearberry N Arctostaphylos rubra – red manzanita N Arctostaphylos uva-ursi – bearberry, kinnikinnick, mealberry Arenaria N Arenaria humifusa – creeping sandwort, low sandwort, spreading sandwort X Arenaria serpyllifolia – thymeleaf sandwort Arethusa N Arethusa bulbosa – dragon's mouth, swamp pink Argemone X Argemone mexicana – Mexican prickly-poppy Arisaema N Arisaema dracontium – green dragon Special Concern N Arisaema triphyllum – Jack-in-the-pulpit Aristida N Aristida basiramea – forktip threeawn Endangered N Aristida dichotoma – Shinner's threeawn N Aristida longespica var. geniculata – red threeawn N Aristida longespica var. longespica – slimspike threeawn X Aristida oligantha – prairie three-awn grass N Aristida purpurascens – arrow feather threeawn Aristolochia X Aristolochia clematitis – birthwort X Aristolochia macrophylla – pipevine Armeria N Armeria maritima – sea thrift, Labrador sea thrift, foxflower Armoracia X Armoracia rusticana – horseradish, red cole Arnica N Arnica angustifolia – narrowleaf arnica, arctic arnica, arctic leopardbane N Arnica chamissonis – meadow arnica, Chamisso's arnica, leafy arnica, leafy leopardbane N Arnica cordifolia – heartleaf arnica, heartleaf leopardbane N Arnica lonchophylla – northern arnica, longleaf arnica, white-plumed arnica, spearleaf arnica Arnoglossum N Arnoglossum platagineum – tuberous Indian-plantain Special Concern Aronia N Aronia melanocarpa – black chokeberry Arrhenatherum X Arrhenatherum elatius – tall oatgrass, French rye, tuber oatgrass, bulbous oatgrass, false oat grass Artemisia X Artemisia abrotanum – southern wormwood, southernwood, lad's love, oldman X Artemisia absinthium – common wormwood, absinthe, absinthe wormwood, European wormwood X Artemisia annua – sweet sagewort, annual wormwood, sweet Annie, sweet wormwood, annual mugwort X Artemisia biennis – biennial wormwood N Artemisia campestris subsp. borealis – boreal wormwood, Canada wormwood N Artemisia campestris subsp. caudata – tall wormwood, beach wormwood, wild wormwood, threadleaf sagewort, sagewort wormwood N Artemisia dracunculus – wild tarragon, dragon wormwood, dragon sagewort, false tarragon, French tarragon, Russian tarragon N Artemisia frigida – fringed sagebrush, prairie sagebrush, fringed sagewort, prairie sagewort, wormwood sage, pasture sage, arctic sagebrush N Artemisia ludoviciana – white sage, silver wormwood, prairie sage, western mugwort, darkleaf mugwort, cudweed sagewort, pasture sage, Louisiana wormwood, Louisiana