| Glebionis segetum | GB, VC16 West Kent, Sevenoaks | John Patrick Micklethwait Brenan | | 19/7/1936 | K |
| Glebionis segetum | GB, VC16 West Kent, Sevenoaks | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 12/9/1937 | K |
| Glebionis segetum | GB, VC16 West Kent, Tunbridge | John Patrick Micklethwait Brenan | | 28/6/1936 | K |
| Glebionis segetum | GB, VC18 South Essex, Dagenham | John Patrick Micklethwait Brenan | | 30/8/1936 | K |
| Glebionis segetum | GB, VC35 Monmouthshire, Chepstow | John Patrick Micklethwait Brenan | | 11/9/1935 | K |
| Glechoma hederacea | GB, VC1 West Cornwall, Ponsanooth | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 26/3/1937 | K |
| Glechoma hederacea | GB, VC15 East Kent, Sellindge | John Patrick Micklethwait Brenan | | 17/4/1936 | K |
| Glechoma hederacea | GB, VC16 West Kent, Tonbridge | John Patrick Micklethwait Brenan | | 5/4/1935 | K |
| Glechoma hederacea | GB, VC17 Surrey, Wisley | John Patrick Micklethwait Brenan Noel Yvri Sandwith | John Patrick Micklethwait Brenan | 6/4/1946 | K |
| Glechoma hederacea | GB, VC33 East Gloucestershire, Coln Saint Aldwyn | John Patrick Micklethwait Brenan Ronald Burn | John Patrick Micklethwait Brenan | 6/5/1941 | K |
| Glechoma hederacea | GB, VC33 East Gloucestershire, Coln Saint Aldwyn | John Patrick Micklethwait Brenan Ronald Burn | John Patrick Micklethwait Brenan | 6/5/1941 | K |
| Groenlandia densa | GB, VC6 North Somerset, Shepton Mallet | John Patrick Micklethwait Brenan | | 12/6/1949 | K |
| Hypochaeris glabra | GB, VC3 South Devon, East Portlemouth | John Patrick Micklethwait Brenan | | 12/6/1938 | K |
| Hypochaeris glabra | GB, VC9 Dorset, Sandford | John Patrick Micklethwait Brenan Norman Douglas Simpson | John Patrick Micklethwait Brenan | 28/6/1942 | K |
| Hypochaeris glabra | GB, VC15 East Kent, Dungeness | John Patrick Micklethwait Brenan | | 20/9/1936 | K |
| Hypochaeris glabra | GB, VC22 Berkshire, Cothill | John Patrick Micklethwait Brenan | | 5/8/1944 | K |
| Hypochaeris glabra | GB, VC22 Berkshire, Cothill | Alan Philip Dalby Jones John Patrick Micklethwait Brenan | | 5/8/1944 | K |
| Hypochaeris glabra | GB, VC22 Berkshire, Cumnor | E W Jones John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 26/7/1948 | K |
| Hypochaeris glabra | IE, VCH40 Co. Londonderry, Magilligan point | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 23/8/1938 | K |
| Kickxia elatine subsp. elatine | GB, VC29 Cambridgeshire, Newmarket | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 5/8/1946 | K |
| Kickxia elatine subsp. elatine | GB, VC41 Glamorganshire, Horton | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 8/9/1958 | K |
| Lamium album | GB, VC16 West Kent, Tonbridge | John Patrick Micklethwait Brenan | | 9/5/1936 | K |
| Lamium purpureum var. hybridum | GB, VC16 West Kent, Hildenborough | John Patrick Micklethwait Brenan | | 28/3/1936 | K |
| Lamium purpureum var. hybridum | GB, VC41 Glamorganshire | John Patrick Micklethwait Brenan | | | K |
| Lamium purpureum var. hybridum | GB, VC41 Glamorganshire, Rhossili | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 4/9/1958 | K |
| Leonurus cardiaca | GB, VC23 Oxfordshire, Oxford | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 21/6/1939 | K |
+ | Leucanthemum lacustre x maximum = L. x superbum | GB, VC59 South Lancashire, Birkdale | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills | 28/7/1959 | MANCH |
+ | Limonium binervosum subsp. anglicum | GB, VC28 West Norfolk, Holme-by-the-Sea | John Norton Mills John Patrick Micklethwait Brenan June R J Mills | John Norton Mills | 8/8/1946 | MANCH |
| Limosella aquatica | GB, VC41 Glamorganshire, Morfa Pool | John Patrick Micklethwait Brenan | | 12/9/1935 | K |
| Linaria repens | GB, VC15 East Kent, Richborough Port | John Patrick Micklethwait Brenan | | 27/8/1936 | K |
| Linaria repens | GB, VC41 Glamorganshire, Llanmadoc | John Patrick Micklethwait Brenan Rex Alan Henry Graham | John Patrick Micklethwait Brenan | 31/8/1958 | K |
| Linaria supina | GB, VC2 East Cornwall, Par Sands | John Patrick Micklethwait Brenan | | 28/8/1934 | K |
| Linaria supina | GB, VC17 Surrey, Kew Cultivated GB, VC2 East Cornwall, Par | John Patrick Micklethwait Brenan | | 1949 | K |
| Linaria supina | GB, VC17 Surrey, Kew Cultivated GB, VC2 East Cornwall, Par | John Patrick Micklethwait Brenan | | 1949 | K |
| Luzula forsteri x pilosa = L. x borreri | GB, VC24 Buckinghamshire, Marlow | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills | 7/6/1957 | MANCH |
| Marrubium vulgare | GB, VC6 North Somerset, Winscombe | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 24/8/1952 | K |
+ | Melampyrum cristatum | GB, VC29 Cambridgeshire, Hardwick Wood | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills June R J Mills | 7/8/1946 | MANCH |
+ | Melampyrum cristatum | GB, VC29 Cambridgeshire, Hardwick Wood | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills June R J Mills | 7/8/1946 | MANCH |
+ | Melampyrum cristatum | GB, VC29 Cambridgeshire, Hardwick Wood | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills June R J Mills | 7/8/1946 | MANCH |
| Melissa officinalis | GB, VC16 West Kent, Tonbridge | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 23/8/1939 | K |