Sibthorpia europaea
Cornish Moneywort
Sicyos edulis
Chayote
Sida acuta
Common Wireweed
Sida rhombifolia
Arrowleaf Sida
Silaum silaus
Pepper-saxifrage
Silene acaulis
Moss Campion
Silene armeria
Sweet-William Catchfly
Silene chalcedonica
Maltese-Cross
Silene conica
Sand Catchfly
Silene dioica
Red Campion
Silene flos-cuculi
Ragged-Robin
Silene gallica
Small-flowered Catchfly
Silene latifolia
White Campion
Silene noctiflora
Night-flowering Catchfly
Silene nutans
Nottingham Catchfly
Silene rupestris
Rock Campion
Silene uniflora
Sea Campion
Silene viscaria
Sticky Catchfly
Silene vulgaris
Bladder Campion
Silybum marianum
Milk Thistle
Sinapis alba
White Mustard
Sinapis arvensis
Charlock
Sison amomum
Stone Parsley
Sisymbrium officinale
Hedge Mustard
Smyrnium olusatrum
Alexanders
Smyrnium perfoliatum
Perfoliate Alexanders
Solandra grandiflora
Showy Chalicevine
Solanum americanum
American Black Nightshade
Solanum chenopodioides
Tall Nightshade
Solanum dulcamara
Bittersweet
Solanum erianthum
Velvet Nightshade
Solanum melongena
Eggplant
Solanum nigrum
Black Nightshade
Solanum nitidibaccatum
Green Nightshade
Solanum torvum
Pendejera
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
Sonneratia caseolaris
Mangrove Apple
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
Sorbus x motleyi
Sparmannia sp.
African Hemp
Spathodea campanulata
African Tulip Tree
Spergula arvensis
Corn Spurrey
Spergularia marina
Lesser Sea-spurrey
Spergularia media
Greater Sea-spurrey
Spergularia rubra
Sand Spurrey
Spergularia rupicola
Rock Sea-spurrey
Spermacoce exilis
False Buttonweed
Spermacoce hispida
Shaggy Buttonweed
Spermacoce remota
Sphagneticola trilobata
Bay Biscayne Creeping-oxeye
Spigelia anthelmia
West Indian Pinkroot
Spiraea canescens
Himalayan Spiraea
Spiraea x rosalba
Intermediate Bridewort
Stachys alpina
Limestone Woundwort