Small mounds of trifoliate leaves with yellow flowers.
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I have added a closeup of a set of stipules. Also, a leaf; I noticed that some of the leaves show faint blotching, so although it's not very prominent and not everywhere, I wondered if this could be Spotted Medick. Rose says Spotted Medick has short-toothed stipules; these look not very short, but I don't know how long the teeth on long-toothed stipules can get. Stace says Spotted Medick stipules are "dentate usually < halfway to midrib" and these are toothed all the way. So it's probably not, despite the spots. The fruits will help, eventually. I got there this morning a yard ahead of the mower, so more samples will have to wait.
The stipules are clearly, I think, toothed less than half-way to the midribs (of the stipules).
Photos 2 and 3 I would say are definitely M. arabica. Is photo 1 definitely the same plant? It does look like M. polymorpha, and Medicago species do like to grow together.
This illustrates the problem for people with the "expert" badge when observations are changed after they have added a name - which cannot be withdrawn. (See the Forum for my strong views on this.) No real complaint in this case, as you have made it clear that you have added new photographs, though I wish iSpot would date additions.
However, if you can, you do need to check that these are from the same plant.
I leave it to Cicuta58 to decide if/how he wants to supplement his initial ID.
The toothing goes nearly all the way to the tip of the stipule where the midrib is. Do you mean that the distance from the midrib to the base of the teeth is greater than the size of the teeth?
I can't say that the second and third photos are definitely from the same plant. I was rushed; there are a dozen patches in the grass in that little area, and the mower was a yard away when I took that sample. I looked at the mown area this morning. In the remaining leafage I could not find a single patch that did not have some lightly blotched leaves. I will see what I can find in a few days' time.
This is not to do with whether the toothing runs to the tips of the stipules, which is the case in both species. The midribs run the lengths of the stipules, as midribs do. Yes, it is the distance from the midrib to the base of the teeth relative to the lengths of the teeth themselves. In M. polymorpha the toothing cuts more than half way to the midribs. In M. arabica, the toothing cuts less than halfway to the midrib, making the teeth relatively shorter. This is how the character is usually given.
In photo 2, the stipules are definitely M. arabica. In the original photo, that Cicuta58 based his identification on, we do not see any clear, complete stipule, but in more that one place in the photo there are visible stipule teeth that are very long and narrow, and appear to be M. polymorpha type. I think Gaeme was right with his original ID.
So you had two Medicago species together, which is not unusual. I once found five species in a single square metre.
Thanks. Yes, I see the stipule teeth too, now that you point them out. I will keep an eye on that patch of grass and see what I can find when fruits start to appear.
Lat/Lng: 51.376353333333, 0.0091233333333333
OS grid ref: TQ399660