• Cerastium glomeratum Sticky Mouse-ear
  
• Cerastium semidecandrum Little Mouse-ear
  
• Ceratophyllum demersum Hornwort
  
• Chamaemelum nobile Chamomile
  
• Chenopodium album Fat-hen
  
• Chenopodium bonus-henricus Good King Henry
  
• Chenopodium rubrum Red Goosefoot
  
• Chrysanthemum segetum Corn Marigold
  
• Chrysosplenium oppositifolium Opposite-leaved Golden-Saxifrage
  
• Cicerbita macrophylla Blue-sow-thistle, Common
  
• Circaea lutetiana Enchanter's-nightshade
  
• Cirsium arvense Thistle, Creeping
  
• Cirsium dissectum Thistle, Bog
  
• Cirsium palustre Thistle, Marsh
  
• Cirsium vulgare Thistle, Spear
  
• Clematis vitalba Traveller's-joy
  
• Clinopodium menthifolium Wood-calamint
  
• Cochlearia danica Scurvygrass, Danish
  
• Cochlearia officinalis Common Scurvygrass
  
• Coeloglossum viride Frog orchid
  
• Conium maculatum Hemlock
  
• Conopodium majus Pignut
  
• Convolvulus arvensis Bindweed, Field
  
• Cornus sanguinea Dogwood
  
• Coronopus didymus Lesser Swine-cress
  
• Coronopus squamatus Swine-cress
  
• Corylus avellana Hazel
  
• Cotoneaster microphyllus Cotoneaster, Small-leaved
  
• Crambe maritima Sea-kale
  
• Crataegus monogyna Hawthorn
  
• Crepis capillaris Smooth Hawk's-beard
  
• Crepis paludosa Marsh Hawk's-beard
  
• Crepis vesicaria Hawk's-beard, Beaked
  
• Crithmum maritimum Rock Samphire
  
• Crocosmia crocosmiflora Montbretia
  
• Cuscuta epithymum Dodder
  
• Cymbalaria muralis Ivy-leaved Toadflax
  
• Cytisus scoparius Broom
  
• Daboecia cantabrica St. Dabeoc's Heath
  
• Dactylorhiza fuchsii Common spotted-orchid
  
• Dactylorhiza fuchsii hebridensis Hebridean spotted-orchid
  
• Dactylorhiza fuchsii okellyi O' Kelly's Orchid
  
• Dactylorhiza incarnata Early-marsh orchid
  
• Dactylorhiza incarnata coccinea Early marsh-orchid
  
• Dactylorhiza incarnata pulchella Early marsh-orchid
  
• Dactylorhiza maculata ericetorum Heath spotted-orchid
  
• Dactylorhiza majalis brevifolia Northern marsh-orchid
  
• Dactylorhiza majalis occidentalis Western marsh-orchid
  
• Dactylorhiza majalis traunsteineroides Narrow-leaved marsh-orchid
  
• Daucus carota Wild Carrot