Like grasses (see grass flower page), sedges have small flowers or florets that lack showy petals. But they also lack the surrounding bracts of the grass floret termed "palea" and "lemma". Rather, a single, small bract or bracteole subtends (is attached below) each floret. A floret and bract alone may constitute a spiklelet, or may be combined with other florets into a spikelet (see below). In the latter, each floret is typically obscured by its bract. The term glume is applied loosely to any of these bracts that occur beneath the floret. This practice differs from the term "glume" as applied in grass taxonomy.

In the photograph at left of Scleria testacea spikelets, each spikelet has but a single floret with a bracteole. The flowers are unisexual (either male or female; flowers are imperfect), so that details of the female floret, at least, are readily observable. This species is monoecious, meaning both male and female flowers occur on the same plant. In our Scleria, the uppermost or terminal floret of each "partial panicle" is pistillate (female). The hypogynium is a cup-like or scale-like structure that surrounds the ovary. The fertilized ovary develops into a fruit called an achene; those shown here are about 2 mm across.

The two spikelets of Eleocharis dulcis (water chestnut) shown in the photograph at the right are displaying anthesis, when the (male) stamens and (female) stigmas are exserted from the floral bracts. Stamens are the prominent yellowish structures extending outward along the lower third of the spikelet—in this case 1 per floret but in some species up to 3. The styles (3 per stigma, in some species 2) are the whitish feathery structures especially evident here in the middle of the spikelet. In this sedge, a spikelet is composed of numerous florets, the floral bracts arranged spirally around the rachis. At anthesis, pollen grains are released from the stamens and distributed by the wind to be captured by the styles, thus fertlizing the ovary of the floret.

As noted above, florets are grouped within a structure called a spikelet (Figures M and N). The spikelet is a basic floral structure, but is less important in sedge taxonomy than is the case for grass taxonomy. Just as in grasses, a sedge flowering structure (the inflorescence) consists of numerous spikelets arranged in a particular manner at the upper end of a vertical stem called the culm or axis (or rachis within the spikelet). In sedges the spikelets can be attached directly to the culm or attached at the ends of small stalks called pedicels. If branched, the terms branch or ray may apply to the part supporting multiple pedicels.

Observing the structure of the infloresence is usually necessary for identifying a sedge species. Fortunately, it is generally the case that not only is the inflorescence easily seen in most sedges, but is nearly always present. One reason for this is that most sedge "plants" are actually part of a single plant growing from a common rhizome, so all ages of plantlets may be represented. Also, sedges tend to grow in wetter environments than grasses, so seasonality is less of a factor in determining flowering. A strategy employed by many grasses is to produce a lot of vegetative parts in the wet months, then start flowering as the season starts to shift to a drier state. Only nut grass (actually "nut sedge"), among commonly encountered sedges in Hawai‘i, seems to have periods when flowers are absent.

Rushes are another category of plants that, like many sedges, are typically associated with streams and wetlands. Indeed, if you stumble upon a true rush, you are likely to assume at first glance that it is some kind of sedge. A few "rushes" are in the Family Cyperaceae, such as bulrush (Schoenoplectus spp.). However, true rushes are classified in the Family Juncaceae and only on examining the inflorescence will you be corrected in your initial assumption.

Rushes prefer somewhat cooler temperatures and are found in wet situations at higher elevations in the Islands. Luzula is somewhat of an exception: found typically on open slopes above 2400 ft (730 m) elevation. The culms of rushes are round in cross-section (terete) or, in a few, laterally compressed. Thus, a culm with "edges" puts your unknown back into the category of a true sedge. Unfortunately, there are sedges (and rushes in Cyperaceae) with terete or weakly angled culms, so you must rely on the structure of the flower itself.

True rushes have flowers with petals and sepals, but these are much reduced and scalelike (or "chaffy"). "Scalelike" means a thin, flat, dry membranous structure (not green). Because the sepals and petals are identical, they are called tepals. The big difference that separates grasses and sedges from rushes is the nature of their fruit. In the former, the fruit has a single seed that is relatively tightly bound to the fruit wall. In rushes, the fruit is a many-seeded capsule; essentially a little container of seeds.

A key to Hawai‘i plants in the Family Juncaceae is now available