Separating Grasses from other Monocots

Most grasses are easily recognizable as such, although members of several other plant families do resemble grasses, and in the absence of flowering structures, could be mistaken for grasses. Flowering plants are divided into dicots (germinating seed produces two seed leaves or cotyledons) and monocots (germinating seeds produce a single seed leaf). Grasses are monocots, and their basic structural characteristics are typical of the majoriity of monocotyledonous plants: leaves with parallel veins, fibrous roots, and other consistent floral and internal structures that differ from those of dicots (see Monocots vs. Dicots or Monocots and Dicots Chart).

Plants that are not grasses—but closely resemble grasses—are very likely other moncots. Sedges (Family Cyperaceae) are the most common grass-like plants encountered in nature. Sedges differ from grasses in a number of respects. Generally, sedges are coarser, the leaves concentrated around the base of a stem (or culm) or occuring as bracts (one or more stem or leaf-like appendages below the flowering heads), or so reduced in size as to appear absent. The culm may be triangular ("sedges have edges") in cross-section and solid, not hollow (although there are hollow culms in the family). Sedges may be more abundant than grasses in wetlands or wet areas.

Rushes of the Family Juncaceae are rather uncommon in Hawai‘i, and more likely to be mistaken for sedges. Bulrush (Schoenoplectus spp.) is actually a sedge with a hollow (and mostly rounded) culm. A few other monocots are named, in common parlance, "grasses", but are not. Mondo grass (Ophiopogon spp., Family Liliaceae) is one. A number of fully aquatic grass-like plants resemble (but are not) grasses, for examples: widgeon grass (Ruppia maritima, Family Ruppiaceae) and tapegrass (Vallisneria spiralis, Family Hydrocharitaceae). These aquatic plants can be keyed out at Vascular Plants; either choose a plant family from the list below the introductory text OR start at couplet [70].

 GRASS BASICS