Samolus valerandi
Brookweed
Sanguisorba officinalis
Great Burnet
Sanicula europaea
Sanicle
Saponaria officinalis
Soapwort
Saxifraga cernua
Drooping Saxifrage
Saxifraga granulata
Meadow Saxifrage
Saxifraga hypnoides
Mossy Saxifrage
Saxifraga spathularis
St Patrick's-cabbage
Saxifraga tridactylites
Rue-leaved Saxifrage
Scabiosa columbaria
Small Scabious
Schedonorus giganteus
Giant Fescue
Schoenoplectus lacustris
Common Club-rush
Schoenoplectus tabernaemontani
Grey Club-rush
Schoenus nigricans
Black Bog-rush
Scilla verna
Spring Squill
Scirpus sylvaticus
Wood Club-rush
Scleranthus annuus
Annual Knawel
Scrophularia auriculata
Water Figwort
Scrophularia nodosa
Common Figwort
Scutellaria galericulata
Skullcap
Scutellaria incarnata
Hoary Skullcap
Scutellaria minor
Lesser Skullcap
Scyphiphora hydrophylacea
Nilad
Sedum acre
Biting Stonecrop
Sedum album
White Stonecrop
Sedum anglicum
English Stonecrop
Seemannia sylvatica
Bolivian Sunset
Senecio inaequidens
Narrow-leaved Ragwort
Senecio sarracenicus
Broad-leaved Ragwort
Senecio squalidus
Oxford Ragwort
Senecio sylvaticus
Heath Groundsel
Senecio viscosus
Sticky Groundsel
Senecio vulgaris
Groundsel
Senega paniculata
Root Beer Plant
Senna fistula
Golden Shower Tree
Serratula tinctoria
Saw-wort
Seseli libanotis
Moon Carrot
Setaria verticillata
Hooked Bristlegrass
Sherardia arvensis
Field Madder
Sibthorpia europaea
Cornish Moneywort
Sicyos edulis
Chayote
Silaum silaus
Pepper-saxifrage
Silene conica
Sand Catchfly
Silene flos-cuculi
Ragged-Robin
Silene gallica
Small-flowered Catchfly
Silene noctiflora
Night-flowering Catchfly
Silene nutans
Nottingham Catchfly
Silene viscaria
Sticky Catchfly
Silene vulgaris
Bladder Campion
Sinapis alba
White Mustard
Sison amomum
Stone Parsley
Sisymbrium officinale
Hedge Mustard
Sisyrinchium bermudiana
Blue-eyed-grass
Sisyrinchium montanum
American Blue-eyed-grass
Smyrnium olusatrum
Alexanders
Smyrnium perfoliatum
Perfoliate Alexanders
Solanum chenopodioides
Tall Nightshade
Solanum dulcamara
Bittersweet
Solanum erianthum
Velvet Nightshade
Solanum nigrum
Black Nightshade
Solanum torvum
Pendejera
Solidago canadensis
Canadian Goldenrod
Solidago gigantea
Early Goldenrod
Solidago virgaurea
Goldenrod
Sonchus asper
Prickly Sow-thistle
Sonneratia caseolaris
Mangrove Apple
Sorbus aucuparia
Rowan
Sorbus cambrensis
Welsh Whitebeam
Sorbus leyana
Ley's Whitebeam
Sorbus minima
Least Whitebeam