| Senecio squalidus | GB, VC21 Middlesex, City of London | Noel Yvri Sandwith | Botanical Society & Exchange Club of The British Isles Royal Botanic Gardens, Kew | 22/6/1944 | SLBI |
| Senecio sylvaticus | GB, VC6 North Somerset, Catcott Burtle | James Walter White | Botanical Society & Exchange Club of The British Isles Job Edward Lousley | 23/8/1927 | SLBI |
+ | Silene conica | GB, VC25 East Suffolk, Felixstowe, Landguard Common | Stephen John Batchelder | Botanical Society & Exchange Club of The British Isles National Museum of Wales | 9/6/1928 | MANCH |
+ | Silene gallica | GB, VC19 North Essex, Colchester,Hythe | George Charles Brown | Botanical Society & Exchange Club of The British Isles | 16/6/1913 | MANCH |
+ | Silene gallica | GB, VC54 North Lincolnshire, Woodhall Spa,High Hall Wood | Arthur Reginald Horwood | Botanical Society & Exchange Club of The British Isles Charles Bailey | 16/9/1915 | MANCH |
+ | Silene gallica | GB, VC113 Channel Islands, Jersey,West Mount | Job Edward Lousley | Botanical Society & Exchange Club of The British Isles Job Edward Lousley | 16/6/1926 | MANCH |
+ | Silene nutans | GB, VC11 South Hampshire, Portsmouth, Fort Cumberland | Patrick Martin Hall | Botanical Society & Exchange Club of The British Isles Patrick Martin Hall | 20/6/1929 | MANCH |
+ | Silene nutans | GB, VC15 East Kent, Lydd | George Claridge Druce | Botanical Society & Exchange Club of The British Isles Charles Bailey | 13/6/1924 | MANCH |
+ | Silene nutans | GB, VC113 Channel Islands, Guernsey,Saint Peters Port | Louis Arsene | Botanical Society & Exchange Club of The British Isles | 18/5/1926 | MANCH |
| Sonchus palustris | GB, VC23 Oxfordshire, Stanton Saint John | George Claridge Druce | Botanical Society & Exchange Club of The British Isles George Claridge Druce William Hunt Painter | 9/1894 | ABS |
| Sorbus bristoliensis | GB, VC6 North Somerset, Leigh Woods | James Walter White | Botanical Society & Exchange Club of The British Isles Douglas Montague Heath Frederick Robinson | 27/5/1922 to 20/7/1922 | BIRM |
+ | Spartina maritima | GB, VC15 East Kent | Charles Edgar Salmon | Botanical Society & Exchange Club of The British Isles Charles Edgar Salmon Willis Openshaw Howarth | 15/9/1924 | MANCH |
| Spergularia marina | GB, VC87 West Perthshire, Clackmannan | Tom Drummond | Botanical Society & Exchange Club of The British Isles William Hadden Beeby | 27/9/1876 | SLBI |
| Stachys | GB, VC41 Glamorganshire, Splott | Royston Leslie Smith | Botanical Society & Exchange Club of The British Isles Charles Edward Britton | 9/1931 | K |
| Stachys | GB, VC41 Glamorganshire, Splott | Royston Leslie Smith | Botanical Society & Exchange Club of The British Isles | 9/1931 | K |
+ | Stachys alpina | GB, VC50 Denbighshire, Cerrig-y-Druidion | Albert Wilson | Botanical Society & Exchange Club of The British Isles | 1/8/1927 | MANCH |
+ | Stachys germanica | GB, VC23 Oxfordshire, Oxford | Harry Joseph Riddelsdell | Botanical Society & Exchange Club of The British Isles Charles Bailey | 17/8/1918 | MANCH |
| Stachys germanica | GB, VC23 Oxfordshire, Woodstock | George Claridge Druce | Botanical Society & Exchange Club of The British Isles | 3/10/1931 | K |
| Stachys sylvatica x palustris = S. x ambigua | GB, VC8 South Wiltshire, Bratton | Joseph Donald Grose | Botanical Society & Exchange Club of The British Isles Joseph Donald Grose | | K |
| Stachys sylvatica x palustris = S. x ambigua | GB, VC17 Surrey, Chessington | Charles Edward Britton | Botanical Society & Exchange Club of The British Isles | 4/8/1929 | MANCH |
| Stachys sylvatica x palustris = S. x ambigua | GB, VC19 North Essex, Berechurch | George Charles Brown | Botanical Society & Exchange Club of The British Isles George Charles Brown Job Edward Lousley | 11/7/1926 | SLBI |
| Stachys sylvatica x palustris = S. x ambigua | GB, VC70 Cumberland, Melmerby | Charles Waterfall | Botanical Society & Exchange Club of The British Isles Charles Waterfall | 31/7/1914 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Chew Magna | James Walter White | Botanical Society & Exchange Club of The British Isles James Walter White | 1/6/1926 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Flax Bourton | James Walter White | Botanical Society & Exchange Club of The British Isles Charles Bailey | 6/1912 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Gatcombe | Ida Mary Roper | Botanical Society & Exchange Club of The British Isles Charles Bailey James Walter White | 23/5/1918 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Gatcombe Mill | Ida Mary Roper | Botanical Society & Exchange Club of The British Isles Charles Bailey Ida Mary Roper | 28/5/1915 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Gatcombe Mill | James Walter White | Botanical Society & Exchange Club of The British Isles | 24/5/1926 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC6 North Somerset, Wraxall | James Walter White | Botanical Society & Exchange Club of The British Isles Charles Bailey James Walter White | 11/6/1915 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC17 Surrey, Godalming | J Comber | Botanical Society & Exchange Club of The British Isles Charles Bailey | 5/1912 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC17 Surrey, Peper Harow | Rowland John Burdon | Botanical Society & Exchange Club of The British Isles Job Edward Lousley | 22/6/1926 | SLBI |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC23 Oxfordshire, Latchford | George Claridge Druce | Botanical Society & Exchange Club of The British Isles Charles Bailey George Claridge Druce | 8/1913 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC28 West Norfolk, Shropham | Frederick Robinson | Botanical Society & Exchange Club of The British Isles Charles Bailey Frederick Robinson | 8/7/1915 | MANCH |
| Symphytum officinale x asperum = S. x uplandicum | GB, VC57 Derbyshire, Matlock | George Claridge Druce | Botanical Society & Exchange Club of The British Isles Charles Bailey George Claridge Druce | 6/1912 | MANCH |
| Taraxacum | GB, VC23 Oxfordshire, Marston | John Frederick Gustav Chapple | Botanical Society & Exchange Club of The British Isles John Frederick Gustav Chapple | 13/5/1936 | SLBI |
| Tephroseris integrifolia | GB, VC52 Anglesey, South Stack | Job Edward Lousley | Botanical Society & Exchange Club of The British Isles Charles Edward Britton Job Edward Lousley | 19/6/1931 | K |
| Teucrium botrys | GB, VC12 North Hampshire, Micheldever | George Claridge Druce | Botanical Society & Exchange Club of The British Isles George Claridge Druce | 9/1930 | K |
| Teucrium botrys | GB, VC12 North Hampshire, Micheldever | George Claridge Druce | Botanical Society & Exchange Club of The British Isles Charles Edward Britton | 9/1930 | K |
| Teucrium botrys | GB, VC17 Surrey, Addington | Job Edward Lousley | Botanical Society & Exchange Club of The British Isles Job Edward Lousley | 27/8/1932 | K |
| Thlaspi caerulescens | GB, VC46 Cardiganshire, Llanrhystyd | Joseph Donald Grose | Botanical Society & Exchange Club of The British Isles Harold Stuart Thompson Joseph Donald Grose | 5/5/1935 | BIRM |
| Thymus | GB, VC2 East Cornwall, Polperro | Francis Rilstone | Botanical Society & Exchange Club of The British Isles Job Edward Lousley | 28/7/1928 | SLBI |