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 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
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
Spathiphyllum blandum
Pleasant Peace Lily
Spathoglottis plicata
Philippine Ground Orchid
Spergularia rubra
Sand Spurrey
Spigelia anthelmia
West Indian Pinkroot
Spiranthes romanzoffiana
Irish Lady's-tresses
Spiranthes spiralis
Autumn Lady's-tresses
Stachys alpina
Limestone Woundwort
Stachys arvensis
Field Woundwort
Stachys byzantina
Lamb's-ear
Stachys germanica
Downy Woundwort
Stachys palustris
Marsh Woundwort
Stachys sylvatica
Hedge Woundwort
Staphylea pinnata
Bladdernut
Stellaria aquatica
Water Chickweed
Stellaria graminea
Lesser Stitchwort
Stellaria neglecta
Greater Chickweed
Stylosanthes guianensis
Stylo
Succisa pratensis
Devil's-bit Scabious
Symphyotrichum lanceolatum
Narrow-leaved Michaelmas-daisy
Symphytum officinale
Common Comfrey
Symphytum orientale
White Comfrey
Symphytum tuberosum
Tuberous Comfrey
Symphytum x hidcotense
Hidcote Comfrey
Symphytum x uplandicum
Russian Comfrey
Synedrella nodiflora
Nodeweed
Tamus communis
Black Bryony
Tanacetum parthenium
Feverfew
Tanacetum vulgare
Tansy
Taraxacum agg.
Dandelion
Taraxacum 'iscanum'
Taraxacum palustre
Taraxacum porteri
Teesdalia nudicaulis
Shepherd's Cress
Tellima grandiflora
Fringecups