Panicum and Steinchisma

1. Spikelets < 1.5 mm long…Steinchisma laxa (Panicum laxum)

1. Spikelets > 1.5 mm long…2

2. Plants rhizomatous saltwater beach and dune species. Spikelets > 4 mm long…P. amarum (large grasses with the inflorescences congested. Leaves to 1 cm wide)

2. Plants not beach species (may be rhizomatous). Spikelets usually < 4 mm long…3

3. Leaves involute and pseudoterete. Inflorescence axes upright…P. tenerum

3. Leaves flat or at least not pseudoterete; inflorescence axes usually spreading, but sometimes upright...(sometimes P. anceps)…4

4. Fertile lemma wrinkled (transversely rugose). Inflorescence branches whorled...Urochloa maxima (aka Panicum maximum) (Usually enormous invasive weeds often > 6’ tall. For additional species with rugose lemmas see Urochloa)

4. Fertile lemmas not transversely rugose. Inflorescence branches whorled or attached singly…5

5. Spikelets distinctly warty…P. verrucosum (wetland species with open airy inflorescences having the spikelets very widely spaced. Spikelets ca. 2 mm long)

5. Spikelets not warty…6

6. Mature spikelets “gaping” (with an open gap at the tip) due to lower palea being indurate (spikelets often gaping also in P. repens, which has a characteristic truncate first glume). When immature, the gaping character may not be apparent, but the upper lemma characteristically papillose…Steinchisma hians (leaf blades often ca. 2-3 mm wide, but can be wider)

6. Mature spikelets not gaping, or if gaping, the lower lemma not indurate (except possibly in P. repens)…7

7. Inflorescence axes upright, the inflorescence more or less cylindric (may be true also of P. anceps but this with a tuft of hairs on the fertile lemma)…P. hemitomon

7. Inflorescence axes spreading…8

8 Lower glume 1.8 mm long or longer…P. virgatum (inflorescences open and airy, the main branches whorled. Spikelets large 3.5-5 mm)

8. Lower glume < 1.8 mm…9

9. Lower glume acute. Fertile lemma with minute tuft of hairs at the apex…10

9. Lower glume truncate or rounded. Fertile lemma with no tuft of hairs apically…11

10. Plants with creeping rhizome resembling a “chicken foot.” Spikelet 2.3-4 mm long. Lower glume 1/3 the spikelet length…P. anceps (incl. P. rhizomatum)

10. Plants not rhizomatous. Spikelet (1.3)1.6-3 mm long. Lower glume half or more the spikelet length…P. rigidulum (spikelets often dark-reddish tinged)

11. Nodes swollen. Leaf blades flat, sometimes (not necessarily) with a conspicuous white midvein. Panicle > 5 cm wide. If "rhizomatous," the apparent rhizome merely a prostrate, rooting culm (not scaly). Spikelets green or reddish…P. dichotomiflorum (highly variable in size. Inflorescence branches usually scabrous. Lower glume truncate)

11. Nodes not swollen. Leaf blades folded, the midveins not white. Panicle usually < 5 cm wide. Plants with a scaly rhizome. Spikelets often white…P. repens (Plants strongly rhizomatous. Leaves all lying in a single plane and often diverging evenly, like rungs in a ladder. Some stems, with their leaves, having a herringbone pattern. Lower glume truncate.)