Flora of North America species comparison

Glyceria striata grows in bogs, along lakes and streams, and in other wet places. Its range extends from Alaska to Newfoundland and south into Mexico. Plants from the eastern portion of the range have sometimes been treated as G. striata var. striata, and those from the west as G. striata var. stricta (Scribn.) Fernald. Eastern plants tend to have somewhat narrower leaves and thinner culms than western plants, but the variation appears continuous. In the west, larger specimens are easy to confuse with G. elata. The two species are sometimes found growing together without hybridizing; this and molecular data (Whipple et al. [in prep.]) support their recognition as separate species. The differences between the two in growth habit and stature are evident in the field; they are not always evident on herbarium specimens. In its overall aspect, G. striata also resembles G. pulchella, but it has somewhat more lax panicle branches in addition to smaller spikelets and florets.

Glyceria xgatineauensis Bowden is a sterile hybrid between G. striata and G. melicaria. It resembles G. melicaria but has longer (up to 12 cm), less appressed panicle branches and is a triploid with 2n = 30. It was described from a population near Eardley, Quebec. An additional specimen, tentatively identified as G. xgatineauensis, was collected in 1929 from French Creek in Upshur County, West Virginia.

Glyceria xottawensis Bowden is a sterile hybrid between G. striata and G. canadensis. It is intermediate between the two parents, and is known only from the original populations near Ottawa. It has sometimes been included in G. xlaxa (Scribn.) Scribn. [=G. canadensis var. laxa]; that taxon often produces viable seed, indicating that it is not a hybrid.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Glyceria includes approximately 35 species, all of which grow in wet areas. All but five species are native to the Northern Hemisphere. The genus is represented in the Flora region by 13 native and 3 introduced species, as well as 3 named hybrids. One additional European species, G. notata, is included in this treatment because it has been reported to be present in the region.

All native species of Glyceria are palatable to livestock. They are rarely sufficiently abundant to be important forage species. Some grow in areas that are soon degraded by grazing. Glyceria maxima can cause cyanide poisoning in cattle. Species in sects. Striatae and Hydropoa have potential as ornamentals.

Glyceria resembles Puccinellia in the structure of its spikelets and its preference for wet habitats; it differs in its inability to tolerate highly alkaline soils, and its usually more flexuous panicle branches, closed leaf sheaths, and single-veined upper glumes. Some species are apt to be confused with Torreyochloa pallida, another species associated with wet habitats but one that, like Puccinellia, has open leaf sheaths. Glyceria includes several species that appear to intergrade. In some cases, the distinctions between such taxa are more evident in the field, particularly when they are sympatric. Recognition of such taxa at the specific level is merited unless it can be shown that all the distinctions between them are inherited as a group.

The three named North American hybrids are Glyceria xgatineauensis Bowden, G. xottawensis Bowden, and G. ×occidentalis (Piper) J.C. Nelson. The first two were named as hybrids; they are not included in the key and are mentioned only briefly in the descriptions. Glyceria ×occidentalis has hitherto been treated as a species. Studies finished shortly before completion of this volume indicate that it, too, consists of hybrids (Whipple et al. [in press]). It is included in the key and provided with a full description.

Culm thickness is measured near midlength of the basal internode; it does not include leaf sheaths. Unless otherwise stated, ligule measurements reflect both the basal and upper leaves. Ligules of the basal leaves are usually shorter than, but similar in shape and texture to, those of the upper leaves. The number of spikelets on a branch is counted on the longest primary branches, and includes all the spikelets on the secondary (and higher order) branches of the primary branch. Pedicel lengths are measured for lateral spikelets on a branch, not the terminal spikelet. Lemma characteristics are based on the lowest lemmas of most spikelets in a panicle. There is often, unfortunately, considerable variation within a panicle.

(Discussion copyrighted by Flora of North America; reprinted with permission.)