Colocasia esculenta Colocasia esculenta 'Black Magic'
Colocasia esculenta 'Fontanesii' Colocasia esculenta 'Hawaiian® Black Coral'
Colocasia esculenta 'Illustris' Colocasia esculenta 'Milky Way'
Colocasia esculenta 'Mojito' Colocasia esculenta 'Nancy's Revenge'
Colocasia esculenta 'Tea Cup' Colocasia gigantea 'Thailand Giant Strain'
Colquhounia coccinea Columnea gloriosa
Columnea schiedeana Commelina coelestis
Conicosia pugioniformis Conicosia pugioniformis ssp. muirii
Conium maculatum Conoclinium coelestinum
Conoclinium greggii Conostylis seorsiflora
Convallaria majalis Convallaria majalis 'Aureo-variegata'
Convallaria majalis 'Striata' Convolvulus althaeoides ssp. tenuissimus
Convolvulus cneorum Convolvulus sabatius
Convolvulus tricolor Convolvulus tricolor 'Royal Ensign'
Cordyline australis Cordyline australis 'Purple Tower'
Cordyline australis 'Red Star' Cordyline australis 'Sundance'
Cordyline banksii 'Sprilecpink (Electric Pink)' Cordyline obtecta
Cordyline terminalis Cordyline terminalis 'Dr. Brown'
Cordyline terminalis 'Exotica' Coreopsis 'Creme Brule'
Coreopsis 'Experimental Coreopsis COR118' Coreopsis 'Limerock Dream'
Coreopsis 'Limerock Passion' Coreopsis 'Limerock Ruby'
Coreopsis 'Tequila Sunrise' Coreopsis auriculata
Coreopsis auriculata 'Nana' Coreopsis auriculata 'Zamphir'
Coreopsis x delphinifolia 'Blue Mirror' Coreopsis gigantea
Coreopsis grandiflora 'Early Sunrise' Coreopsis grandiflora 'Heliot'
Coreopsis grandiflora 'Sunray' Coreopsis grandiflora 'Walcoreop(Flying Saucers ™)'
Coreopsis integrifolia Coreopsis lanceolata
Coreopsis lanceolata 'Baby Sun' Coreopsis lanceolata 'Goldfink'
Coreopsis lanceolata 'Sterntaler' Coreopsis rosea
Coreopsis rosea 'Alba' Coreopsis rosea 'American Dream'
Coreopsis rosea 'Sweet Dreams' Coreopsis verticillata 'Golden Gain'
Coreopsis verticillata 'Golden Showers' Coreopsis verticillata 'Grandiflora'
Coreopsis verticillata 'Moonbeam' Coreopsis verticillata 'Zagreb'
Cornukaempferia aurantiflora 'Jungle Gold' Cornus canadensis
Cortaderia selloana Cortaderia selloana 'Aureolineata'
Cortaderia selloana 'Aureo-Picta' Cortaderia selloana 'Pumila'
Cortaderia selloana 'Silver Comet' Cortaderia selloana 'White'
Cortaderia toetoe Corydalis elata 'Rhythm 'n' Blues'
Corydalis flexuosa 'Blue Panda' Corydalis flexuosa 'China Blue'
Corydalis flexuosa 'Purple Leaf' Corydalis lutea
Corydalis lutea 'Alba' Corydalis ochroleuca
Corynephorus canescens 'Spiky Blue' Coryphantha elephantidens
Coryphantha erecta Cosmos atrosanguineus
Costus barbatus Costus comosus
Costus curvibracteatus Costus cuspidatus
Costus malortieanus Costus pictus
Costus pulverulentus Costus speciosus
Costus speciosus 'Nova' Costus speciosus 'Variegatus'
Costus varzearum Costus woodsonii
Cotula coronopifolia Cotyledon orbiculata