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 anglica
English Whitebeam
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
Spergularia rubra
Sand Spurrey
Spergularia rupicola
Rock Sea-spurrey
Spiraea x rosalba
Intermediate Bridewort
Spiranthes romanzoffiana
Irish Lady's-tresses
Spiranthes spiralis
Autumn Lady's-tresses
Spirodela polyrhiza
Greater Duckweed
Stachys arvensis
Field Woundwort
Stachys germanica
Downy Woundwort
Stachys sylvatica
Hedge Woundwort
Stellaria alsine
Bog Stitchwort
Stellaria aquatica
Water Chickweed
Stellaria holostea
Greater Stitchwort
Stellaria nemorum
Wood Stitchwort
Stellaria palustris
Marsh Stitchwort
Streptocarpus saxorum
False African Violet
Stuckenia pectinata
Fennel Pondweed
Succisa pratensis
Devil's-bit Scabious
Swietenia macrophylla
Mahogany
Symphyotrichum lanceolatum
Narrow-leaved Michaelmas-daisy
Symphytum officinale
Common Comfrey
Symphytum orientale
White Comfrey
Symphytum x hidcotense
Hidcote Comfrey
Symphytum x uplandicum
Russian Comfrey
Syntrichia ruralis
Sand-hill Screw-moss
Tamus communis
Black Bryony
Tanacetum vulgare
Tansy
Taraxacum agg.
Dandelion
Taraxacum britannicum
Taraxacum falcatum
Dandelion
Taraxacum palustre
Taraxacum Section Ruderalia
Dandelion
Taxus baccata
Yew