Silene uniflora
Sea Campion
Silene viscaria
Sticky Catchfly
Silene vulgaris
Bladder Campion
Sison amomum
Stone Parsley
Sisyrinchium bermudiana
Blue-eyed-grass
Solanum dulcamara
Bittersweet
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 rupicola
Rock 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
Spiranthes romanzoffiana
Irish Lady's-tresses
Spiranthes spiralis
Autumn Lady's-tresses