The common yellow-flowered Medicago species of Texas

Several months ago, I went through a lot of the Medicago observations. I learned a lot about how to tell them apart without fruits, but have since forgotten. Because of this, I have decided to write the information down as I relearn it so that when I do forget, I'll be able to relearn more quickly.

M. lupulina: The species with the most observations and the only yellow-flowered species listed here that has more than 10 flowers per inflorescence. The stipules not lacerate. Fruit without prickles.
M. minima: Stipules not lacerate. Fruits with prickles. Hairy on the upper sides of leaves (and often densely so).
M. polymorpha: Stipules regularly lacerate, less deeply lacerate than M. orbicularis; margin usually not undulating making it relatively easy to detirmine the form of the stipule. Fruits prickled. Not hairy on upper sides of leaves.
M. orbicularis: Stipules irregularly and deeply lacerate, the lacera on the margins often undulating making it difficult to determine the form. Fruits not prickled.

Other Medicago species:
M. arabica: Few flowered. Reddish spot in the middle of each leaflet (apparently fading later in the growing season). Shallowly lacerate stipules. Fruits with prickles.
M. falcata: Many flowered. Similar to a yellow version of Alfalfa (M. sativa). Fruits not curled (falcate) at maturity.
M. sativa (Alfalfa): Many purplish flowers. This is probably easier to confuse with some of the native purple-flowered legumes than the other Medicago species found here.
M. x varia: Hybrid between M. sativa and M. falcata.

My understanding of M. falcata is not as good as the others, but it seems like a pretty distinctive species that needs little more than what is provided to ID. Let me know if you think otherwise. It is also much less common than the others if the number of observations is anything to go by.

Posted on November 30, 2017 09:51 PM by nathantaylor nathantaylor


Looks like I got all the Texas species represented here. BONAP doesn't even have M. falcata listed yet. The observation for Texas doesn't have fruits, but I suppose that's it. Whether it is or not, I don't think it hurts to list it here. The observation can be found here.

Posted by nathantaylor over 6 years ago

Yet another wonderful entry -- bookmarking!

Posted by sambiology over 6 years ago

Notes like this are great to have, thanks

Posted by janetwright over 6 years ago

Here's the guide to the common yellow-flowered Medicago species of New Mexico:

Medicago lupulina.

Posted by aspidoscelis over 6 years ago

I'll have to find another species in NM just to make things more complicated for you. ;)

Posted by nathantaylor over 6 years ago

We do have Medicago minima and Medicago polymorpha, but I haven't seen either one yet.

Posted by aspidoscelis over 6 years ago

comment on M. arabica: that characteristic red spot will eventually fade to a pigmentless blotch as the season progresses

Posted by ellen5 over 6 years ago

@ellen5 Euphorbia maculata acts the same late in the fall. Hopefully, the stipules will be enough to distinguish for those individuals. I'll make the comment.
@aspidoscelis Good to know you're not completely left out. :) I guess you're just going to have to spend more time in lawns.

Posted by nathantaylor over 6 years ago

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