Culms 20-200 cm tall, 1-8 mm thick, erect or geniculate at the lower nodes; nodes glabrous or pilose; internodesglabrous. Sheaths shorter than the internodes, keeled, glabrous or pilose, hairs near the throat papillose-based; liguleswith a 0.1-2 mm membranous base and 0.10–3 mm ciliate fringe; blades (6)20-75 cm long, 1.5–15 mm wide. Panicles9-75 cm long, width to about 2/3 length; branches straight or flexible, strongly ascending to reflexed; pedicels 0.2-5 mm. Spikelets 2.5-5.5 mm long, 1-2 mm wide. Lower glumes 1.2-3.5 mm, 1/2-4/5 as long as the spikelets, 3-5-veined; upper glumes 1.4–4 mm; lower florets sterile or staminate; lower lemmas 2.9–3.3 mm; upper florets 2.1–5 mm long, 1-1.5 mm wide, lemma apices puberulent. 2n = 36, 54, 70, 72.

Zuloagaea bulbosa grows in roadside ditches, on gravelly river banks and moist mountain slopes, often in ponderosa pine and oak woodlands, from southern Nevada and Arizona to western Texas and central Mexico. It is considered an important forage grass and is sometimes cut for hay but is not known to be cultivated. Flowering is from July to mid-October.

In the past, three species have been recognized within Panicum sect. Bulbosum. Bess et al. (2006) demonstrated that the variation is continuous and highly influenced by environment. Their recommendation, that Hopia be treated as a unispecific genus, is followed here. Plants growing in sunlight tend to have purple spikelets, those growing in the shade tend to have green spikelets.