Saxifraga rosacea
Irish Saxifrage
Saxifraga spathularis
St Patrick's-cabbage
Saxifraga tridactylites
Rue-leaved Saxifrage
Saxifraga x polita
False Londonpride
Scabiosa columbaria
Small Scabious
Schedonorus giganteus
Giant Fescue
Schoenoplectus lacustris
Common Club-rush
Schoenoplectus tabernaemontani
Grey Club-rush
Schoenus nigricans
Black Bog-rush
Scilla autumnalis
Autumn Squill
Scilla bifolia
Alpine Squill
Scilla forbesii
Glory-of-the-snow
Scilla siberica
Siberian Squill
Scilla verna
Spring Squill
Scirpoides holoschoenus
Round-headed Club-rush
Scirpus sylvaticus
Wood Club-rush
Scleranthus annuus
Annual Knawel
Scleranthus perennis
Perennial Knawel
Scleroderma aerolatum
Leopard Earthball
Scorzoneroides autumnalis
Autumn Hawkbit
Scrophularia auriculata
Water Figwort
Scrophularia nodosa
Common Figwort
Scrophularia umbrosa
Green Figwort
Scutellaria galericulata
Skullcap
Scutellaria minor
Lesser Skullcap
Scutellinia scutellata
Eyelash Cup
Secale cereale
Rye
Sedum acre
Biting Stonecrop
Sedum album
White Stonecrop
Sedum anglicum
English Stonecrop
Sedum sexangulare
Tasteless Stonecrop
Selaginella selaginoides
Lesser Clubmoss
Senecio inaequidens
Narrow-leaved Ragwort
Senecio sarracenicus
Broad-leaved Ragwort
Senecio squalidus
Oxford Ragwort
Senecio sylvaticus
Heath Groundsel
Senecio viscosus
Sticky Groundsel
Senecio vulgaris
Groundsel
Sequoia sempervirens
Coastal Redwood
Sequoiadendron giganteum
Wellingtonia
Serratula tinctoria
Saw-wort
Seseli libanotis
Moon Carrot
Setaria viridis
Green Bristle-grass
Sherardia arvensis
Field Madder
Sibthorpia europaea
Cornish Moneywort
Silaum silaus
Pepper-saxifrage
Silene acaulis
Moss Campion
Silene armeria
Sweet-William Catchfly
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 uniflora
Sea Campion
Silene viscaria
Sticky Catchfly
Silene vulgaris
Bladder Campion
Silybum marianum
Milk Thistle
Simethis mattiazzii
Kerry Lily
Sinapis alba
White Mustard
Sinapis arvensis
Charlock
Sison amomum
Stone Parsley
Sisymbrium officinale
Hedge Mustard
Sisyrinchium bermudiana
Blue-eyed-grass
Sisyrinchium montanum
American Blue-eyed-grass
Smyrnium olusatrum
Alexanders
Solanum chenopodioides
Tall Nightshade
Solanum dulcamara
Bittersweet
Solanum nigrum
Black Nightshade