Athrotaxis Athyrium Atriplex Attalea Aubrieta Aucuba Aulax Auranticarpa Aurinia Austrocedrus Austrocylindropuntia Austrostipa Averrhoa Avicennia Azadirachta Azalea Azara Azolla (aquatic ferns) Azorella Azorina Aztekium Azetura B Babiana Baccharis Backhousia Bacopa (water hyssop) Bactris Baeckea Baikiaea Baileya Ballota Balsamorhiza (balsam root) Bambusa (bamboo) Banksia Baptisia an orchid genus Barbarea (yellow rocket or winter cress) Barkeria (an orchid genus) Barleria Barklya (gold blossom tree) Barnadesia Barringtonia Bartlettina Basselinia Bassia Bauera Bauhinia Baumea × Beallara an orchid hybrid genus Beaucarnea Beaufortia Beaumontia Beccariella Bedfordia Begonia Belamcanda Bellevalia Bellis (daisy) Bellium Berberidopsis Berberis (barberry) Berchemia Bergenia Bergerocactus Berkheya Berlandiera Berrya Bertolonia Berzelia Beschorneria Bessera Beta (beet) Betula (birch) Biarum Bidens Bignonia Bikkia Billardiera Billbergia Bischofia Bismarckia Bixa Blandfordia Blechnum (hard fern) Bletilla (an orchid genus) Blighia Bloomeria Blossfeldia Bocconia Boenninghausenia Bolax Bolbitis Bollea (an orchid genus) Boltonia Bolusanthus Bomarea Bombax Bongardia Boophone Borago Borassodendron Borassus Boronia Bosea Bossiaea Bothriochloa Bougainvillea Bouteloua Bouvardia Bowenia Bowiea Bowkeria Boykinia Brabejum Brachychiton Brachyglottis Brachylaena Brachypodium Brachyscome Brachysema Brachystelma Bracteantha Brahea (hesper palm) Brassavola (an orchid genus) Brassaia (octopus tree) Brassia (an orchid genus) Brassica (mustard, cabbage) × Brassidium (hybrid orchids) × Brassocattleya (hybrid orchids) × Brassolaeliocattleya (trigeneric hybrid orchids) Breynia Briggsia Brillantaisia Brimeura Briza (quaking grass) Brodiaea Bromelia Broughtonia an orchid genus Broussonetia Browallia Brownea Browningia Bruckenthalia Brugmansia Brunfelsia Brunia Brunnera Brunsvigia Brya Buchloe Buckinghamia Buddleja Buglossoides Bulbine Bulbinella Bulbocodium Bulbophyllum (an orchid genus) Bulnesia Bunchosia Buphthalmum Bupleurum Burchardia Burchellia × Burrageara an orchid hybrid genus Burretiokentia Bursaria Bursera Burtonia Butea Butia Butomus Buxus (boxwood) Byrsonima Bystropogon C Cabomba Cadia Caesalpinia (dwarf poinciana, Pride of Barbados) Caladium Calamagrostis (reed grass, smallweed) Calamintha (calamint) Calamus Calandrinia Calanthe an orchid genus Calathea Calceolaria (slipperwort) Calendula (pot marigold) Calibanus Calibrachoa Calla Calliandra Callianthemum Callicarpa (beauty berry) Callicoma (black wattle) Callirhoe (poppy mallow) Callisia Callistemon (bottlebrush) Callistephus (Chinese aster) Callitriche (water starwort) Callitris (cypress pine) Calluna (heather) Calocedrus (incense cedar) Calochone Calochortus Calodendrum (cape chestnut) Calomeria Calophaca Calophyllum Calopyxis Caloscordum Calothamnus Calotropis Calpurnia Caltha (kingcup, marsh marigold) Calycanthus Calymmanthium Calypso (an orchid genus) Calytrix (starflower) Camassia (quamash) Camellia Camoensia Campanula (bellflower) Campsis (trumpet vine) Campylotropsis (See Lespedeza) Cananga (ylang ylang) Canarina Canistrum Canna Cantua Capparis Capsicum (pepper) Caragana (peashrub) Caralluma Cardamine (bittercress) Cardiocrinum Cardiospermum Cardwellia Carex (sedge) Carissa Carlina Carludovica Carmichaelia Carnegiea (saguaro) Carpentaria Carphalea Carpinus (hornbeam) Carpobrotus Carthamus (safflower) Carum (caraway) Carya (hickory, pecan) Caryopteris Caryota (fishtail palm) Cassia (shower tree) Cassinia Cassiope Cassipourea Castanea (chestnut) Castanopsis Castanospermum (black bean) Casuarina (sheoak)