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
Sparganium erectum
Branched Bur-reed
Sparganium natans
Least Bur-reed
Sparmannia sp.
African Hemp
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
Spiraea x rosalba
Intermediate Bridewort
Spiranthes spiralis
Autumn Lady's-tresses
Stachys arvensis
Field Woundwort
Stachys byzantina
Lamb's-ear
Stachys germanica
Downy Woundwort
Stachys palustris
Marsh Woundwort