| Geum rivale x urbanum = G. x intermedium | GB, VC50 Denbighshire, Llangollen | W Horton-Smith | | 3/6/1917 | MANCH |
| Geum rivale x urbanum = G. x intermedium | GB, VC83 Midlothian, Edinburgh, Colinton Dell | W Horton-Smith | | 7/7/1878 | MANCH |
| Gnaphalium uliginosum | GB, VC58 Cheshire, Winnington | W Horton-Smith | | 13/8/1915 | MANCH |
| Gnaphalium uliginosum | GB, VC28 West Norfolk, Fakenham | | W Horton-Smith | | MANCH |
| Helleborus foetidus | GB, VC58 Cheshire, Hartford Cultivated | W Horton-Smith | | 28/2/1924 | MANCH |
| Helleborus foetidus | GB, VC58 Cheshire, Hartford | W Horton-Smith | | 28/2/1924 | MANCH |
+ | Hydrocharis morsus-ranae | GB, VC58 Cheshire, Witton | W Horton-Smith | Schill W Horton-Smith | 8/1918 | MANCH |
+ | Hydrocharis morsus-ranae | GB, VC28 West Norfolk, Fakenham | W Horton-Smith | W Horton-Smith | | MANCH |
+ | Hydrocharis morsus-ranae | GB, VC58 Cheshire, Witton | W Horton-Smith | W Horton-Smith | 8/1918 | MANCH |
+ | Hyoscyamus niger | GB, VC83,VC84, Edinburgh,Cramond Island | W Horton-Smith | W Horton-Smith | 2/8/1880 | MANCH |
+ | Hyoscyamus niger | GB, VC85 Fifeshire | W Horton-Smith | W Horton-Smith | 23/6/1877 | MANCH |
+ | Hyoscyamus niger | GB, VC28 West Norfolk, Fakenham,Hempton Green | | W Horton-Smith | | MANCH |
+ | Hyoscyamus niger | GB, VC58 Cheshire | John Harbord Lewis | W Horton-Smith | 30/9/1871 | MANCH |
| Hypericum androsaemum x hircinum = H. x inodorum | GB, VC62 North-east Yorkshire, Scarborough | W Horton-Smith | | 15/9/1916 | MANCH |
| Hypericum androsaemum x hircinum = H. x inodorum | GB, VC50 Denbighshire, Llangollen Cultivated | W Horton-Smith | | 1/9/1919 | MANCH |
| Hypericum androsaemum x hircinum = H. x inodorum | GB, VC50 Denbighshire, Llangollen Cultivated | W Horton-Smith | | 2/8/1920 | MANCH |
+ | Hypericum montanum | GB, VC51 Flintshire, Llandulas | W Horton-Smith | W Horton-Smith | 29/7/1917 | MANCH |
+ | Impatiens glandulifera | GB, VC58 Cheshire, Ashley (E of),Castle Mill | W Horton-Smith | W Horton-Smith | 1841 | MANCH |
+ | Impatiens glandulifera | GB, VC50 Denbighshire, Bangor on Dee | W Horton-Smith | | 6/8/1917 | MANCH |
+ | Impatiens glandulifera | GB, VC58 Cheshire, Farndon | W Horton-Smith | | 20/8/1916 | MANCH |
| Inula conyzae | GB, VC50 Denbighshire, Llangollen | W Horton-Smith | W Horton-Smith | 26/8/1919 | MANCH |
| Inula conyzae | GB, VC51 Flintshire, Mold | W Horton-Smith | W Horton-Smith | 3/9/1916 | MANCH |
| Inula conyzae | GB, VC34 West Gloucestershire, Redbrook | W Horton-Smith | | 7/9/1922 | MANCH |
| Inula conyzae | GB, VC58 Cheshire, Kelsborrow Castle | W Horton-Smith | | 17/8/1916 | MANCH |
| Iris foetidissima | GB, VC50 Denbighshire, Llandegla GB, VC50 Denbighshire, Ruthin | W Horton-Smith | Schill | 24/7/1922 | MANCH |
| Jasione montana | GB, VC28 West Norfolk, Fakenham | | W Horton-Smith | | MANCH |
| Juncus inflexus x effusus = J. x diffusus | GB, VC50 Denbighshire, Horseman's Green | W Horton-Smith | | 6/8/1917 | MANCH |
| Juncus inflexus x effusus = J. x diffusus | GB, VC58 Cheshire, Winsford | W Horton-Smith | | 19/7/1916 | MANCH |
| Juncus inflexus x effusus = J. x diffusus | GB, VC58 Cheshire, Hatchmere | W Horton-Smith | | 2/7/1919 | MANCH |
+ | Lathyrus palustris | GB, VC29 Cambridgeshire, Wicken | W Horton-Smith | W Horton-Smith | 2/9/1924 | MANCH |
| Legousia hybrida | GB, VC28 West Norfolk, West Barsham | | W Horton-Smith | | MANCH |
+ | Lychnis alpina | GB, VC90 Angus, Little Kilrannoch [Little Gilrannoch] | David J Powrie | W Horton-Smith | 7/1878 | MANCH |
+ | Lychnis viscaria | GB, VC83 Midlothian, Edinburgh | W Horton-Smith | W Horton-Smith | 6/1877 | MANCH |
+ | Medicago minima | GB, VC26 West Suffolk, Wangford, Lakenheath | Arthur Bennett | W Horton-Smith | 6/1878 | MANCH |
+ | Melampyrum cristatum | GB, VC28 West Norfolk, Colkirk Wood | W Horton-Smith | Manchester Museum | | MANCH |
| Melica uniflora | GB, VC28 West Norfolk, Colkirk | W Horton-Smith | | | MANCH |
+ | Mentha arvensis x aquatica = M. x verticillata | GB, VC28 West Norfolk, Fakenham | W Horton-Smith | W Horton-Smith | | MANCH |
+ | Minuartia verna | GB, VC51 Flintshire, North Hendre | W Horton-Smith | W Horton-Smith | 18/5/1919 | MANCH |
+ | Minuartia verna | GB, VC83 Midlothian, Edinburgh, Queens Park | W Horton-Smith | W Horton-Smith | 26/6/1877 | MANCH |
+ | Myosurus minimus | GB, VC10 Isle of Wight, Ryde | J B Salter | W Horton-Smith | 5/1839 | MANCH |