Panicum niihauense is a cespitose (growing in tufts or clumps) perennial grass that grows 50–125 cm tall, with unbranched and puberulent culms (aerial stems) 50 to 125 cm (20 to 49 in) long and pubescent nodes. Its leaves are simple, alternate, and cauline, with blades 15–35 cm long and 0.1–1.9 cm wide, displaying a flat and velvety puberulent surface, with the upper surface sometimes glabrous. It produces terminal panicles that are 13–35 cm long, with a puberulent axis, at least below, and branches that are appressed to the rachis and scaberulous. The spikelets (pictured) are 2.6–3.2 mm long, acuminate, and glabrous, with the first glume usually slightly shorter than the second, both acuminate and nerved. The first floret is sterile, with the first lemma as long as or shorter than the first glume, and the second floret is elliptic, glossy, and smooth. The anthers measure 0.9–1.2 mm in length. The fruit of this grass is a caryopsis, primarily found on rare dunes or rocky knolls between 10–15 meters.
Bean-shaped (Reniform): Resembling the shape of a kidney or bean.
Square or Oblong: Angular shape with all sides more or less equal or longer than wide.
Triangular: Three-sided shape, broadest below the middle.
Elliptic: Rounded at both ends. shaped like an ellipse or oval.
Ovate or Obovate: egg-shaped, broader at one end.
Linear: Extremely long and narrow, with sides usually parallel.
Round: Appears circular, with length and width roughly the same.
Cardioid (Heart-Shaped): One edge has a prominent double curve into two lobes.
Cylindrical: A cylinder with parallel sides and a circular cross-section.
Discoid: Resembling a disc or plate with two relatively flat surfaces.
Fusiform: Spindle-shaped, tapering at both ends.
Globose: Spherical.
Lenticular: Resembling a lens with two convex surfaces.
Ovoid: Egg-shaped.
Plano-convex: Having a flat ventral (planar) surface and a curved dorsal (convex) surface.
Polygonal: Having more than three flat faces meeting at angles.
Sectoroid: Resembling a segment of an orange with two relatively flat faces and one curved face.
Subglobose/ellipsoid: Inflated shape but less than spherical.
Trigonous: Having three faces that meet at a distinct angle; triangular in cross-section.
Endangered species (E) are species that are so rare they’re in danger of becoming extinct.
Threatened species (T) are species that are likely to become endangered within the foreseeable future throughout all or a significant portion of their range.
Species of Concern (SOC) are species about which there are some concerns regarding status and threats, but insufficient information is available to list the species under the Endangered Species Act (ESA).
Plant Extinction Prevention (PEP) is a state status for rare plants that focuses its efforts on species that have fewer than 50 remaining wild individuals.
Orthodox seeds (desiccation-tolerant): can be dried to an internal seed moisture of less than 12% water and stored at freezing temperatures.
Intermediate seeds (temperature-sensitive) tend to age faster than orthodox seeds and may have only a 5-year lifespan when stored at -20°C. They are recommended for storage at 5°C.
Recalcitrant seeds (desiccation-sensitive): cannot be stored in a conventional freezer as they cannot survive after drying and/or freezing at -20°C. They are recommended for cryopreservation storage.