Sanguisorba officinalis
Great Burnet
Sanicula europaea
Sanicle
Saponaria officinalis
Soapwort
Saxifraga granulata
Meadow Saxifrage
Saxifraga hypnoides
Mossy Saxifrage
Saxifraga oppositifolia
Purple Saxifrage
Saxifraga spathularis
St Patrick's-cabbage
Saxifraga tridactylites
Rue-leaved Saxifrage
Scabiosa columbaria
Small Scabious
Schedonorus giganteus
Giant Fescue
Schismatoglottis calyptrata
Dukaruk
Schoenoplectus tabernaemontani
Grey Club-rush
Schoenus nigricans
Black Bog-rush
Scilla autumnalis
Autumn Squill
Scilla verna
Spring Squill
Scirpus sylvaticus
Wood Club-rush
Scleranthus annuus
Annual Knawel
Scleranthus perennis
Scorzoneroides autumnalis
Autumn Hawkbit
Scrophularia auriculata
Water Figwort
Scrophularia nodosa
Common Figwort
Scutellaria galericulata
Skullcap
Secale cereale
Rye
Sedum acre
Biting Stonecrop
Sedum anglicum
English Stonecrop
Sedum sexangulare
Tasteless Stonecrop
Selaginella selaginoides
Lesser Clubmoss
Selenicereus undatus
Pitahaya
Senecio sarracenicus
Broad-leaved Ragwort
Senecio squalidus
Oxford Ragwort
Senecio viscosus
Sticky Groundsel
Senecio vulgaris
Groundsel
Sequoia sempervirens
Coastal Redwood
Sequoiadendron giganteum
Wellingtonia
Serratula tinctoria
Saw-wort
Sherardia arvensis
Field Madder
Sibthorpia europaea
Cornish Moneywort
Silaum silaus
Pepper-saxifrage
Silene acaulis
Moss Campion
Silene dioica
Red Campion
Silene flos-cuculi
Ragged-Robin
Silene gallica
Small-flowered Catchfly
Silene noctiflora
Night-flowering Catchfly
Silene uniflora
Sea Campion
Silene viscaria
Sticky Catchfly
Silene vulgaris
Bladder Campion
Sinapis alba
White Mustard
Sinapis arvensis
Charlock
Sison amomum
Stone Parsley
Sisymbrium officinale
Hedge Mustard
Sisyrinchium bermudiana
Blue-eyed-grass
Smyrnium olusatrum
Alexanders
Solidago canadensis
Canadian Goldenrod
Solidago virgaurea
Goldenrod
Sonchus asper
Prickly Sow-thistle
Sorbus aria
Common Whitebeam
Sorbus aucuparia
Rowan
Sorbus cambrensis
Welsh Whitebeam
Sorbus leptophylla
Thin-leaved Whitebeam
Sorbus minima
Least Whitebeam
Sorbus porrigentiformis
Grey-leaved Whitebeam
Sorbus rupicola
Rock Whitebeam
Sorbus stenophylla
Llanthony Whitebeam
Sorbus torminalis
Wild Service-tree
Sparganium angustifolium
Floating Bur-reed
Sparganium erectum
Branched Bur-reed
Sparganium natans
Least Bur-reed
Spergula arvensis
Corn Spurrey
Spergularia marina
Lesser Sea-spurrey
Spergularia media
Greater Sea-spurrey