Chaenactis douglasii var. douglasii
Chaenactis glabriuscula var. glabriuscula
Chaenactis glabriuscula var. heterocarpha
Chamaebatia australis
Chamaebatia foliolosa
Chamaebatiaria millefolium
Chamaesaracha nana
Chamerion angustifolium
Chamerion angustifolium ssp. circumvagum
Chamerion latifolium
Cheilanthes bonariensis
Cheilanthes fendleri
Cheilanthes gracillima
Cheilanthes intertexta
Chenopodium album
Chimaphila menziesii
Chimaphila umbellata
Chionanthus retusus
Chiranthodendron pentadactylon
Chlorogalum pomeridianum
Chorizanthe membranacea
Chorizanthe xanti var. xanti
Chrysanthemum coronarium
Chrysolepis sempervirens
Chrysothamnus viscidiflorus ssp. viscidiflorus
Cichorium intybus
Circaea alpina ssp. pacifica
Cirsium andersonii
Cirsium arizonicum var. arizonicum
Cirsium occidentale var. californicum
Cirsium occidentale var. candidissimum
Cirsium palustre
Cirsium scariosum var. americanum
Cirsium vulgare
Cistus albidus
Cistus incanus ssp. corsicus
Cistus purpureus
Cistus salvifolius
Citharexylum hidalguense
Clarkia biloba ssp. biloba
Clarkia cylindrica ssp. clavicarpa
Clarkia dudleyana
Clarkia gracilis ssp. albicaulis
Clarkia heterandra
Clarkia lassenensis
Clarkia modesta
Clarkia purpurea ssp. quadrivulnera
Clarkia rhomboidea
Clarkia rubicunda
Clarkia unguiculata
Clarkia williamsonii
Claytonia lanceolata
Claytonia nevadensis
Claytonia parviflora ssp. grandiflora
Claytonia parviflora ssp. parviflora
Claytonia perfoliata ssp. perfoliata
Claytonia rubra
Claytonia rubra ssp. rubra
Cleistocactus straussii
Clematis lasiantha
Clematis ligusticifolia
Clematis viticella
Clematis sp. seeds
Cleomella arborea var. globosa
Clerodendrum splendens
Clianthus puniceus
Clinopodium vulgare
Clintonia andrewsiana
Coleogyne ramosissima
Coleus lanuginosis
Colletia paradoxa
Collinsia childii
Collinsia heterophylla var. heterophylla
Collinsia sparsiflora var. collina
Collinsia tinctoria
Collinsia torreyi var. torreyi
Collinsia torreyi var. wrightii
Collomia grandiflora
Collomia heterophylla
Collomia rawsoniana
Colutea arborescens
Comandra umbellata ssp. californica
Comarostaphylos arbutoides
Comarostaphylos diversifolia var. planifolia
Comarum palustre
Conium maculatum
Consolida sp.
Convolvulus althaeoides
Convolvulus arvensis
Convolvulus cantabrica
Convolvulus sp.
Corallorhiza maculata
Corallorhiza striata
Cordylanthus rigidus ssp. rigidus
Cordylanthus tenuis ssp. tenuis
Coreopsis tinctoria
Corethrogyne filaginifolia
Cornus capitata
Cornus controversa
Cornus florida
Cornus florida var. urbiniana
Cornus kousa
Cornus nuttallii
Cornus paucinervis
Cornus sericea ssp. occidentalis
Cornus sericea ssp. sericea
Coronilla varia
Coronilla sp.
Corydalis flexuosa
Corylus cornuta ssp. californica
Cosmos bipinnatus
Cotinus coggygria
Cotoneaster aff. pannosus
Cotyledon orbiculata
Crassula aquatica
Crassula multicava
Crataegus pinnatifida
Crepis acuminata
Crepis occidentalis ssp. pumila
Crinum asiaticum
Crinum bulbispermum
Crocanthemum scoparium
Crocus sativus
Crossosoma californicum
Crotalaria sp.
Croton setiger
Cryptantha affinis
Cryptantha confertiflora
Cryptantha echinella
Cryptantha flaccida
Cryptantha simulans
Cryptogramma cascadensis
Cryptogramma sp.
Cucurbita foetidissima
Cuphea sp.
Cupressus sempervirens
Cuscuta subinclusa
Cuscuta sp.
Cyathodes parviflora
Cyclamen africanum
Cylindropuntia prolifera
Cylindropuntia sp.
Cymbalaria muralis
Cymbidium mastersii
Cymopterus terebinthinus var. petraeus
Cynara cardunculus
Cynoglossum amabile
Cynoglossum grande (see Adelinia grandis)
Cynoglossum occidentale (see Andersonglossum occidentale)
Cyperus papyrus
Cyperus sp.
Cypripedium californicum
Cypripedium fasciculatum
Cypripedium montanum
Cypripedium sp.
Cystopteris fragilis
Cytisus scoparius