| Melissa officinalis | GB, VC41 Glamorganshire, Roath | Cecil Ivry Sandwith John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 6/8/1937 | K |
| Mentha arvensis | GB, VC14 East Sussex, Broadwater Forest | John Patrick Micklethwait Brenan | | 25/7/1935 | K |
| Mentha arvensis x aquatica = M. x verticillata | GB, VC5 South Somerset, Triscombe | John Patrick Micklethwait Brenan | | 23/9/1957 | K |
| Mentha arvensis x aquatica = M. x verticillata | GB, VC5 South Somerset, Triscombe | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 23/9/1957 | K |
| Mentha arvensis x aquatica = M. x verticillata | GB, VC14,VC15,VC16, Hawkhurst | John Patrick Micklethwait Brenan | | 3/8/1935 | K |
| Mentha arvensis x aquatica = M. x verticillata | GB, VC23 Oxfordshire, Oxford,Port Meadow | John Patrick Micklethwait Brenan Noel Yvri Sandwith | | 30/8/1941 | K |
| Mentha arvensis x aquatica x spicata = M. x smithiana | GB, VC33 East Gloucestershire, Compton Abdale | John Patrick Micklethwait Brenan | | 10/4/1936 | K |
| Mentha spicata | GB, VC6 North Somerset, Weston | John Patrick Micklethwait Brenan | | 4/9/1936 | K |
| Mentha spicata x suaveolens = M. x villosa var. alopecuroides | GB, VC6 North Somerset, Bath,Twerton | John Patrick Micklethwait Brenan | | 25/8/1935 | K |
| Mentha spicata x suaveolens = M. x villosa var. alopecuroides | GB, VC6 North Somerset, Croscombe | John Patrick Micklethwait Brenan | | 15/10/1944 | K |
| Mentha spicata x suaveolens = M. x villosa var. alopecuroides | GB, VC6 North Somerset, Bowlish GB, VC6 North Somerset, Croscombe | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 15/10/1944 | K |
| Mentha spicata x suaveolens = M. x villosa | GB, VC6 North Somerset, Publow | John Patrick Micklethwait Brenan | | 3/9/1935 | K |
| Mentha spicata x suaveolens = M. x villosa | GB, VC23 Oxfordshire, Freeland | Alan Philip Dalby Jones John Patrick Micklethwait Brenan | | 3/9/1944 | K |
| Mentha spicata x suaveolens = M. x villosa var. alopecuroides | GB, VC41 Glamorganshire, Horton | John Patrick Micklethwait Brenan | | 5/6/1958 | K |
| Mentha spicata x suaveolens = M. x villosa var. alopecuroides | GB, VC41 Glamorganshire, Horton | John Patrick Micklethwait Brenan | | 5/6/1958 | K |
| Mentha suaveolens | GB, VC41 Glamorganshire, Cardiff, Cardiff Docks | Cecil Ivry Sandwith John Patrick Micklethwait Brenan | | 11/9/1935 | K |
| Mentha x piperita var. vulgaris | GB, VC5 South Somerset, Triscombe | John Patrick Micklethwait Brenan | | 23/9/1957 | K |
| Monotropa hypopitys | GB, VC23 Oxfordshire, Nettlebed | Herbert Kenneth Airy Shaw J S Hughes John Patrick Micklethwait Brenan | | 24/10/1937 | K |
+ | Myriophyllum verticillatum | GB, VC30 Bedfordshire | John Norton Mills John Patrick Micklethwait Brenan | Botanical Exchange Club of The British Isles | 11/8/1906 | MANCH |
| Myriophyllum verticillatum | GB, VC30 Bedfordshire, Eaton Socon | John Frederick Gustav Chapple John Patrick Micklethwait Brenan | Druce Herbarium, Oxford | 11/8/1946 | SLBI |
+ | Peucedanum palustre | GB, VC6 North Somerset, Shapwick | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills | 4/8/1944 | MANCH |
| Phalaris arundinacea | GB, VC6 North Somerset, Cheddar | John Patrick Micklethwait Brenan | | 8/7/1944 | K |
| Phalaris arundinacea | GB, VC6 North Somerset, Cheddar | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 8/7/1944 | K |
| Phalaris arundinacea | GB, VC16 West Kent, Tonbridge | John Patrick Micklethwait Brenan | | 28/6/1936 | K |
| Plantago arenaria | GB, VC17 Surrey, Kew | John Patrick Micklethwait Brenan | | 12/8/1955 | K |
| Plantago coronopus | GB, VC6 North Somerset, Steep Holm | Cecil Ivry Sandwith John Patrick Micklethwait Brenan | | 30/5/1937 | K |
| Plantago coronopus | GB, VC10 Isle of Wight, Freshwater | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | | K |
| Plantago lanceolata var. sphaerostachya | GB, VC6 North Somerset | John Patrick Micklethwait Brenan | | 11/7/1946 | K |
| Plantago lanceolata var. sphaerostachya | GB, VC6 North Somerset, Shipham Bottom | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 11/7/1946 | K |
| Plantago lanceolata var. bakeri | GB, VC22 Berkshire, Cumnor | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 3/6/1940 | K |
| Plantago lanceolata var. bakeri | GB, VC22 Berkshire, Cumnor | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 3/6/1940 | K |
| Plantago lanceolata | GB, VC59 South Lancashire, Ainsdale | John Norton Mills John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 28/7/1959 | K |
| Plantago maritima | GB, VC66 County Durham, Teesdale | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 16/7/1938 | K |
+ | Potamogeton compressus | GB, VC59 South Lancashire, Manchester,Droylsden | John Patrick Micklethwait Brenan | John Norton Mills | 27/7/1959 | MANCH |
| Potamogeton friesii x crispus = P. x lintonii | GB, VC16 West Kent, River Darent | John Patrick Micklethwait Brenan | Botanical Society & Exchange Club of The British Isles John Patrick Micklethwait Brenan | 17/9/1946 | SLBI |
| Potamogeton friesii x crispus = P. x lintonii | GB, VC16 West Kent, Riverhead | John Patrick Micklethwait Brenan | Job Edward Lousley | 17/9/1946 | SLBI |
| Potamogeton friesii x crispus = P. x lintonii | GB, VC16 West Kent, Riverhead | John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 17/9/1946 | SLBI |
| Potamogeton polygonifolius | GB, VC6 North Somerset, Shapwick | John Norton Mills John Patrick Micklethwait Brenan | John Norton Mills | 4/7/1944 | MANCH |
| Ranunculus aquatilis | GB, VC23 Oxfordshire, Menmarsh | John Frederick Gustav Chapple John Patrick Micklethwait Brenan | John Patrick Micklethwait Brenan | 29/4/1937 | SLBI |
| Rubus lettii | IE, VCH38 Co. Down, Banbridge | John Patrick Micklethwait Brenan Norman Douglas Simpson | Norman Douglas Simpson | 1/8/1938 | SLBI |