Solanum nigrum
Black Nightshade
Solanum nitidibaccatum
Green Nightshade
Soldanella alpina
Alpine Snowbell
Soleirolia soleirolii
Mind-your-own-business
Solidago canadensis
Canadian Goldenrod
Solidago gigantea
Early Goldenrod
Solidago virgaurea
Goldenrod
Sonchus arvensis
Perennial Sow-thistle
Sonchus asper
Prickly Sow-thistle
Sonchus oleraceus
Smooth Sow-thistle
Sorbus aria
Common Whitebeam
Sorbus aucuparia
Rowan
Sorbus cambrensis
Welsh Whitebeam
Sorbus leptophylla
Thin-leaved Whitebeam
Sorbus leyana
Ley's 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
Spartina anglica
Common Cord-grass
Spergula arvensis
Corn Spurrey
Spergularia marina
Lesser Sea-spurrey
Spergularia media
Greater Sea-spurrey
Spergularia rubra
Sand Spurrey
Spergularia rupicola
Rock Sea-spurrey
Sphagnum denticulatum
Cow-horn Bog-moss
Spiraea canescens
Himalayan Spiraea
Spiraea x rosalba
Intermediate Bridewort
Spiranthes romanzoffiana
Irish Lady's-tresses
Spiranthes spiralis
Autumn Lady's-tresses
Spirodela polyrhiza
Greater Duckweed
Splachnum ampullaceum
Cruet Collar-moss
Stachys arvensis
Field Woundwort
Stachys germanica
Downy Woundwort
Stachys palustris
Marsh Woundwort
Stachys sylvatica
Hedge Woundwort
Staphylea pinnata
Bladdernut
Stellaria alsine
Bog Stitchwort
Stellaria aquatica
Water Chickweed
Stellaria graminea
Lesser Stitchwort
Stellaria holostea
Greater Stitchwort
Stellaria media
Common Chickweed
Stellaria neglecta
Greater Chickweed
Stellaria palustris
Marsh Stitchwort
Stereum gausapatum
Bleeding Oak Crust
Stereum hirsutum
Hairy Curtain Crust
Stropharia semiglobata
Dung Roundhead
Stuckenia pectinata
Fennel Pondweed
Suaeda maritima
Annual Sea-blite
Succisa pratensis
Devil's-bit Scabious
Symphoricarpos albus
Snowberry
Symphyotrichum lanceolatum
Narrow-leaved Michaelmas-daisy
Symphytum asperum
Rough Comfrey
Symphytum officinale
Common Comfrey
Symphytum orientale
White Comfrey
Symphytum x hidcotense
Hidcote Comfrey
Symphytum x uplandicum
Russian Comfrey
Syntrichia ruralis
Sand-hill Screw-moss
Tamarix gallica
Tamarisk
Tamus communis
Black Bryony
Tanacetum parthenium
Feverfew
Tanacetum vulgare
Tansy
Taraxacum agg
Dandelion
Taraxacum agg.
Taraxacum britannicum
Taraxacum falcatum
Dandelion