Simethis mattiazzii
Kerry Lily
Sisyrinchium bermudiana
Blue-eyed-grass
Sisyrinchium montanum
American Blue-eyed-grass
Solanum dulcamara
Bittersweet
Soleirolia soleirolii
Mind-your-own-business
Solidago canadensis
Canadian Goldenrod
Solidago gigantea
Early Goldenrod
Solidago virgaurea
Goldenrod
Sonchus arvensis
Perennial Sow-thistle
Sorbus aria
Common Whitebeam
Sorbus aucuparia
Rowan
Sorbus minima
Least Whitebeam
Sorbus rupicola
Rock 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
Spergularia media
Greater Sea-spurrey
Spergularia rupicola
Rock Sea-spurrey
Spiranthes romanzoffiana
Irish Lady's-tresses
Spiranthes spiralis
Autumn Lady's-tresses
Spirodela polyrhiza
Greater Duckweed
Stachys alpina
Limestone Woundwort