No telling what this one is yet. No rhizomes. Inflorescences are a compact panicle, but you would never know it until you started poking around under a microscope. The inflorescence is a "brush" of awns. The glumes are quite ordinary. The awns are all on the lemmas and the spikelets have several florets. That is what we learn from a quick peek under the microscope.
I am going to cop out for now on using the keys and try just leafing through the photos in my manual of California grasses. Bromus macritensis is a candidate (Foxtail brome). Hordeum jubatum (Foxtail barley) looks similar, but the book says that the glumes have awns (and mine do not) and we know that Hordeum has florets in trios. Foxtail Brome may also be called Bromus rubens (red brome) or B. macritensis var. rubens.
Feeling somewhat confident about this, I drag out the Jepson Guide. Page 1426 for the genus "Bromus". Let's run through the key for the genus
The first question is whether the spikelet is strongly flattened. I will say no, this also goes along with the lemma not being keeled, but rounded over the midrib.
The next question asks if the lemma tip is conspicuously 2 toothed. My lemmas have a prominent stiff awn, but at the base of that, the lemma is translucent and papery and indeed there are two long thin "teeth".
The next question is whether the awn is twisted or straight, mine is dead straight.
Now I am supposed to measure the lemma and awn. Measuring both from the base of the floret, I get the lemma at 15mm and the awn at 30mm. The first branch in the key is for lemma greater than 20 and awn 30-65 -- my specimen is clearly not that big (that would be B. diandrus). The next question asks if the inflorescence is dense or open (mine is dense). This gives us B. madritensis and there are two subspecies.
To distinguish the subspecies, it asks about the length of inflorescence branches. In subsp madritensis the inflorescence branches are visible, whereas in subsp rubens they are hidden because the inflorescence is denser. I would say that my specimen is the latter.
Arizona Flora shows B. rubens and B. madritensis as distinct species. Both are introduced from Europe and found in "roadsides and waste places". I still haven't found a native grass! Interestingly the key in Arizona Flora asks if the culm is glabrous or pubescent below the panicle. Mine is pubescent, which would indicate B. rubens, confirming what we decided using the California key above.
Tom's Plant pages / tom@mmto.org