* Abelia
* Abeliophyllum (white forsythia)
* Abelmoschus (okra)
* Abies (fir)
* Abromeitiella (obsolete)
* Abronia (sand verbena)
* Abutilon
* Acacia (wattle)
* Acaena
* Acalypha
* Acantholimon
* Acanthophoenix
* Acanthus
* Acca
* Acer (maple)
* Achillea (yarrow)
* Achimenantha (hybrid genus)
* Achimenes
* Acinos (calamint)
* Aciphylla
* Acmena
* Acoelorraphe (saw palm)
* Acokanthera
* Aconitum (aconite, monkshood)
* Acorus
* Acrocomia
* Actaea (baneberry)
* Actinidia (kiwifruit)
* Ada
* Adansonia
* Adenia
* Adenium
* Adenocarpus
* Adenophora
* Adenostoma
* Adiantum (maidenhair fern)
* Adlumia
* Adonis
* Adromischus
* Aechmea
* Aegopodium
* Aeonium
* Aerangis (an orchid genus)
* Aerides (an orchid genus)
* Aeschynanthus
* Aesculus (buckeye, horse-chestnut)
* Aethionema
* Agapanthus
* Agapetes
* Agastache
* Agathis
* Agave
* Ageratum
* Aglaonema
* Agonis
* Agrostemma (corn cockle)
* Agrostis
* Aichryson
* Ailanthus
* Aiphanes
* Aira (hair grass)
* Ajania
* Ajuga (bugleweed)
* Akebia
* Alangium
* Albizia (silk tree)
* Albuca
* Alcea (hollyhock)
* Alchemilla
* Aleurites
* Aliceara (hybrid genus)
* Alisma (water plantain)
* Alkanna
* Allamanda
* Allium (onion)
* Alluaudia
* Alnus (alder)
* Alocasia
* Aloe
* Aloinopsis
* Alopecurus (foxtail grass)
* Aloysia
* Alpinia (ginger lily)
* Alsobia
* Alstroemeria
* Alternanthera
* Althaea
* Alyogyne
* Alyssum
* Amaranthus
* Amarcrinum (hybrid genus)
* Amarygia (hybrid genus)
* Amaryllis
* Amberboav
* Amelanchier
* Amesiella
* Amherstia
* Amicia
* Ammi
* Ammobium
* Amorpha
* Amorphophallus
* Ampelopsis
* Amsonia
* Anacampseros
* Anacyclus
* Anagallis (pimpernel)
* Ananas (pineapple)
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* Anaphalis
* Anchusa
* Andromeda
* Andropogon
* Androsace
* Anemone (windflower)
* Anemonella
* Anemonopsis
* Anemopaegma
* Anethum (dill)
* Angelica
* Angelonia
* Angophora
* Angraecum (an orchid genus)
* Anguloa (an orchid genus)
* Angulocaste (hybrid genus)
* Anigozanthos
* Anicacanthus
* Anisodontea
* Anoda
* Anomatheca
* Anopterus
* Anredera
* Antennaria
* Anthemis
* Anthericum
* Anthriscus
* Anthurium
* Anthyllis
* Antigonon
* Antirrhinum (snapdragon)
* Aphelandra
* Aphyllanthes
* Aponogeton
* Aporocactus
* Aporoheliocereus (hybrid genus)
* Aptenia
* Aquilegia (columbine)
* Arabis (rock cress)
* Arachnis (scorpion orchid)
* Araeococcus
* Aralia
* Araucaria (monkey-puzzle)
* Araujia
* Arbutus (madrone)
* Archontophoenix (king palm)
* Arctostaphylos (bearberry, manzanita)
* Arctotheca
* Arctotis (African daisy)
* Ardisia
* Areca
* Arenaria (sandwort)
* Arenga
* Argemone (prickly poppy)
* Argyranthemum
* Argyreia
* Argyroderma
* Ariocarpus
* Arisaema
* Arisarum
* Aristea
* Aristolochia
* Armoracia
* Arnebia
* Arnica
* Aronia (chokeberry)
* Arrabidaea
* Arrhenatherum (oat grass)
* Artemisia (mugwort, sagebrush, wormwood)
* Arthropodium
* Arum
* Aruncus
* Arundinaria
* Arundo
* Asarina
* Asarum (wild ginger)
* Asclepias (milkweed, silkweed)
* Ascocenda (hybrid genus) (an orchid genus)
* Asimina
* Asparagus
* Asperula (woodruff)
* Asphodeline
* Asphodelus (asphodel)
* Aspidistra
* Asplenium
* Astelia
* Aster
* Asteranthera
* Astilbe
* Astilboides
* Astragalus (milk vetch)
* Astrantia
* Astrophytum
* Atherosperma
* Athrotaxis
* Athyrium
* Atriplex
* Aubrieta
* Aucuba
* Aurinia
* Austrocedrus
* Azalea
* Azara
* Azolla
* Azorella
* Azorina
* Aztekium
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