Grass flowers (called florets) are very small, too small for their detailed structure to be seen by the unaided eye. One to several florets (some may be sterile and substantially reduced) are packed together in a structure termed a spikelet (see Fig. 4A), which is the basic unit of the flower or seed head (termed an inflorescence; see also Page v). Both the spikelet and the arrangement of spikelets on the inflorescence provide useful diagnostic characters for identifying grasses. So important is the inflorescence and details of its structure, that a grass plant not in flower could be very difficult to identify. Grass keys that encompass a limited number of species may rely on the structure of the leaf, particularly at the blade/sheath boundary called the collar (see Fig. 1A on page 1). However, this approach may also require magnification. Where our key presents a structural detail of the grass requiring magnification (for examples, using a dissecting microscope, magnifying lens, or lupe), the first lead of a couplet has this magnifying lens symbol:

The grass inflorescence is usually borne at the upper end of a stem called the culm or axis, above the leaves in one of three arrangement types: panicle, spike, or raceme. Spikelets attached not to an axis (termed a rachis in the inflorescence) but to side branches (rays or peduncles), form an inflorescence type termed a panicle. Most grass species have an inflorescence that is technically a panicle. Species described as having spikes or racemes, typically have a culm (the axis) with spicate or racemose branches, so the term panicle is used in our key to indicate a flowering structure that is clearly branched as in Fig. 4B (below, far left). You can read more about open panicle inflorescences on page 14. Excellent drawings are provided by this website: UC IPM Online.

A raceme is an unbranched inflorescence with spikelets attached by short stalks (pedicels) to the rachis. Spikelets that are sessile—attached directly to the rachis without pedicels or branches—form a spike (an example is shown in Fig. 4A, above). Because pedicels can be very short, the distinction between spikes and racemes is not always an easy one to determine in the field; on the other hand, this distinction is a technicality compensated for in our key by not requiring a decision where the pedicels are extremely short.

Grass plant with numerous separate inflorescences, some terminal (from end of culm) and others axillary (from a lower node, arising inside the leaf sheath); each inflorescence consisting of an ovoid (egg-shaped), 1/4 inch (5 to 15 mm) green, purple, or (at maturity) lusterous white or bluish, hard cupule on a stout peduncle and supporting two racemes: one male (with anthers) and one female. { A large grass with wide leaves, found typically in or very near streams (Figs. 4C, 4H, 4I). Job's tears, pū‘ohe‘ohe [HAW - NAT] [FACW]; bilen [GUM - NAT] [FACW]

   Coix lacryma-jobi L.

Not as above. Grass plant with but one or with multiple separate inflorescences associated with a culm. Inflorescence not having a fruit-like, hard cupule supporting two spikelets .. .

Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult.

Not as above .. .

Upon a very close examination, spikelets can be seen enclosed in the uppermost leaf sheaths, such that only filaments and/or stigmas are exposed (Figs. 4F and 4G). { forming dense growth from rhizomes and stolens in dry to mesic open areas. Popular pasture forage at higher elevations on Maui and Hawai‘i Islands. USDA noxious weed. Kikuyu grass [HAW - NAT] [FACU]

Cenchrus clandestinus (Hochst. ex Choiv.) Morrone