Yep, Tom nailed it as Crimson Clover. A quick google search and it looks like a perfect match. I had thrown in the garden a desert tortoise seed mix from Native Seeds and it must have been in that batch. It took over a good part of my tiny garden and I haven't seen it there before.
I have four desert tortoises that I inherited. They apparently ate mostly Kale and lawn grass prior to the adoption.. I'm trying to broaden their diet by growing different desert seed blends. I would also like to plant some succulents but am a bit overwhelmed at all the choices available...