Trifolium dubium vs Look Alikes
From www.naturespot.org.uk
https://gobotany.nativeplanttrust.org/dkey/trifolium/
http://www.namethatplant.net/4DCGI/Query?scientificname=Trifolium
https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&highlighttaxonid=65985#K39894L3a
Trifolium dubium
Low to short, usually hairy with spreading to ascending stems. Trifoliate, leaflets oval to heart shaped, the terminal leaflet short-stalked. Flowers yellow, becoming browner with age, small 2 to 3 mm in small heads with up to 6 flowers.
Standards are ridged like a roof and fold down either side of the pods, unlike Trifolium campestre. Flowers brighter and smaller than Hop Trefoil. When not in fruit, both trefoils are similar to Black Medick in flower, but Black Medick leaves are much more hairy and have an apiculate point (i.e a short fine 'needle' from the end of the leaflet)
Hop Trefoil - Trifolium campestre
Short, hairy, erect plant. Trifoliate, leaflets oval, narrowed towards the base, the central one short stalked. Flowers pale yellow, becoming pale brown eventually, 4 to 5 mm long in small, globose, stalked heads to 15 mm across.
Broad, flat standards that fold downwards over the pods, looking a bit like a hop-flower. Larger and paler than Lesser Hop-trefoil, and turns brownish with age. Both trefoils are similar to Black Medick in flower, but Black Medick leaves are much more hairy and have an apiculate point (i.e a short fine 'needle' from the end of the leaflet)
Slender Trefoil - Trifolium micranthum
It has between 2 and 6 small yellow flowers in each head which helps to distinguish it from Lesser trefoil (T. dubium) which has up to 15.
Black Medick - Medicago lupulina
Low, often prostrate, hairy plant. Leaves are trifoliate and widest above the middle, with a nerve protruding at the broad end of each leaflet in the centre. Flowers yellow, 2 to 3 mm, many to a raceme. Pods coiled, sickle or kidney shaped, 1.5 to 3 mm, black when ripe
If there aren't any fruits, distinguished from the Hop-trefoils by the apiculate leaves - i.e. with a short fine 'needle' at the apex of the leaf. The leaves are also much hairier than the leaves of Hop-trefoils.
