Flora of North America species comparison

Festuca versuta grows in moist, shaded sites on rocky slopes in open woods, from Oklahoma and Arkansas to Texas. It is an uncommon species.

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

Festuca is a widespread genus, probably having more than 500 species. The species grow in alpine, temperate, and polar regions of all continents except Antarctica. There are 37 species native to the Flora region, 2 introduced species that have become established, and 5 introduced species that are known only as ornamentals or waifs. One species, E rubra, is represented by both native and introduced subspecies.

Many native species provide good forage in western North American grasslands and montane forests. Important cultivated species include Festuca rubra, grown for forage and as a turf grass, and F. trachyphylla, used as a turf grass and for erosion control. Both these species have been widely introduced to many parts of the world. A number of species are cultivated as ornamentals—including F. amethystina L., F. cinerea Vill., F. drymeia Mert. & W.D.J. Koch, F. elegans Boiss., F. gautbieri (Hack.) K. Richt., F. glauca Vill., F. kasmiriana Stapf, F. mairei St.-Yves, F. muelleri Vickery, F. pollens Host, F. pseudoeskia Boiss., F. rupicaprina (Hack.) A. Kern., F. spectabilis Jan, and F. varia Haenke. These species have not become established in the Flora region; only F. amethystina and F. glauca are included in this account.

The distribution of some taxa that are grown for turf, revegetation, and, to a lesser extent, horticulture—such as Festuca rubra subsp. rubra, F. trachyphylla, F. filiformis, and F. valesiaca—is continually expanding because of their wide commercial availability. The occurrence of these in the Flora region is no doubt much more extensive than current herbarium collections indicate.

The taxonomy of the genus is problematic and contentious, and this treatment is far from definitive. Keying the species ultimately relies on characters that are sometimes difficult to detect on herbarium specimens, such as ovary pubescence and leaf blade sclerenchyma patterns. Because of the intraspecific variability in many characters, combinations of overlapping characters must be employed for identification.

The distribution of sclerenchyma tissue within the vegetative shoot leaves is often an important diagnostic character in Festuca. Taxa in a small region can often be identified reliably without resorting to consideration of these patterns but, for the Flora region as a whole, their use is essential. These patterns should be observed in cross sections made from mature, but not senescent, leaves of vegetative shoots, xh to halfway up the blades; they can be made freehand, with a single-edged razor blade. Sections are best viewed at 40x or greater magnification, and with transmitted light (polarized if possible). Important features seen in the blade cross section are identified in Fig. 1, p. 390.

There are five main sclerenchyma distribution patterns in Festuca (Fig. 2, above). Almost all species have a strand of sclerenchyma tissue along the margins and opposite the midvein against the abaxial epidermis (Fig. 2C). Strands may be narrow (about as wide as the adjacent veins or narrower, Fig. 2D) to broad (wider than the adjacent veins, Fig. 2E). Additional strands are often present at the abaxial surface opposite the veins; these strands may be confluent (Figs. 1, 2E), sometimes combining to form a cylinder around the leaf and appearing as a continuous ring or band in the cross sections (Figs. 2F, I). Some species have additional strands on the adaxial surface opposite some or all of the veins (Figs. 2G, H). Another variant is for the abaxial sclerenchyma strands to extend inwards to some or all of the vascular bundles (veins), forming pillars in the cross sections (Figs. 2H, I). If both the abaxial and adaxial strands extend inward to the vascular bundles, they are said to form girders (Figs. 2A, B, I).

Some of the patterns described may co-occur within a leaf. For instance, some veins may be associated with pillars, others with girders; some sclerenchyma strands within a leaf may be confluent, whereas others are not. Although there may be considerable variation in the extent of sclerenchyma development, the general pattern within a species is usually constant. It is this that makes such patterns useful diagnostic characters, particularly for those needing to identify plants in vegetative condition. They have not, however, been examined for all species.

Descriptions of leaf blades are based on the leaves of the basal vegetative shoots, where present. For those without basal tufts of vegetative shoots, the cauline leaves are described. Width measurements are provided for leaves that are usually flat, or almost so, when encountered in the field or herbarium. "Diameter" is given for leaves that are usually folded or conduplicate when encountered; for leaves that are oval in cross section when folded, it is the largest diameter (or width).

Closure of the leaf sheaths should be checked on young leaves, because the sheaths often split with age, leading to underestimations of the extent of their closure. The fraction of the leaf sheath that is closed varies within and between species of Festuca, but the species can be divided into three categories in this regard: those such as F. rubra, in which the leaves are closed for at least 3/4 their length; those such as F. saximontana, in which they are closed from 1/3 to slightly more than 1/2 their length; and those such as F. tracbypbylla, in which they are not closed or closed for less than 1/4 their length. The descriptions indicate to which of these categories each species belongs. Lemma awns tend to be longer, and should be measured, on the distal florets within a spikelet.

Under adverse conditions, many species may proliferate vegetatively, where leafy bulbils or shoots form in place of some or all spikelets. Some populations of Festuca are largely (or completely) sterile, reproducing almost entirely through such bulbils, a process termed pseudovivipary. Pseudoviviparous plants may be common or even abundant in certain areas and habitats. Since these stabilized forms are largely reproductively isolated, often of unusual ploidy, and largely morphologically distinct, they are treated as separate species. Although the lower bracts in pseudoviviparous spikelets are usually more or less normal in form, they are sometimes elongated or distorted, as are the upper bracts.

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