Florets and caryopses in this group of taxa have many similar morphological features, some of which can make them indistinguishable.

The general floret shape among all the similar species is narrowly teardrop-shaped (lanceolate), dorsal-ventrally compressed and slightly in-rolled on the palea side; the lemma tapers to a narrow point that usually extends into an awn. The awn is fragile and easily broken, especially in commercial seed lots so florets may appear to be awnless. The lemma wraps around to cover the margins of the palea, but usually leaves the palea keels exposed. Floret sizes within the spikelet are usually larger near the base of the spikelet and get smaller toward the tip of the spikelet. Floret size ranges among the similar species overlap; however, F. rubra and F. heterophylla tend to be longer and wider than florets of F. ovina and F. trachyphylla, and the florets of F. filiformis are the smallest in this group.

The papery lemmas and paleas are about the same colour among the similar species as they are represented by various shades of yellowish-brown and are sometimes tinged with purple or green shading. The lemmas can be smooth to hairy.

For this group of species, the palea is nearly equal in length to the lemma, the two palea keels are in-rolled, and the central part of the palea is recessed in the lower half. The palea is a bit more translucent than the lemma and the dark caryopsis is visible through the palea in mature florets. According to Musil (1963), in F. trachyphylla the palea appears to be more opaque than F. ovina; it may be possible to identify bulk samples of these two species, but the individual seeds appear to be indistinguishable.

The caryopses within this group of similar species are narrowly oblong-oval and pointed at the embryo end, dorsal-ventrally compressed and slightly in-rolled forming a longitudinal groove on the hilum side. Surface texture of the caryopses are smooth to slightly rough, dull to slightly shiny. In this group the tip of the caryopsis (end opposite the embryo) is not hairy, except in F. heterophylla the caryopsis tip is hairy. The embryo is about one-fifth the length of the caryopsis and is in the lateral position (Martin 1946). The hilum is long and linear and about three-fourths the length of the caryopsis. The endosperm is described as solid (Terrell 1971).

The separation of similar looking seeds of Festuca rubra and F. ovina may be achieved by the root fluorescence test, in which young seedlings are sprayed with an ammonia solution and roots of F. rubra will appear yellow-green and roots of F. ovina will appear bluish green under ultraviolet light (ISTA 2022).

Refer to the comparison chart for morphological differences among the similar species. The size measurements provided in the comparison table are based on seed herbarium material located at the California Department of Food and Agriculture (specimens accession numbers are provided for each species).

 

Festuca filiformis Pourr.

[Festuca capillata Lam.; F. tenuifolia Sibth.]

Hair fescue, fine-leaf sheep fescue, fine-leaved fescue, slender fescue

*Note: minimum and maximum sizes are based on 12 florets and five caryopses in a normal range of this species using image measurement protocol (ISMA 2020). CDA-S-23358.

 

Festuca heterophylla Lam.

[Festuca rubra L. var. heterphylla (Lam.) Mutel]

Various-leaved fescue, shade fescue

*Note: minimum and maximum sizes are based on 13 florets and one caryopsis in a normal range of this species using image measurement protocol (ISMA 2020). CDA-S-23305.

 

Festuca rubra L. subsp. commutata Markgr.-Dann.

[Festuca nigrescens Lam.; Festuca rubra L. subsp. fallax auct.]

Chewings fescue, chewing’s fescue

*Note: minimum and maximum sizes are based on combined five samples with a random selection of 36 florets and 22 caryopses in normal range of this species using image measurement protocol (ISMA 2020). CDA-S-23403, CDA-S-23384, CDA-S-23415

 

Festuca rubra L. subsp. rubra

[Festuca rubra L. var. rubra]

Red fescue, creeping red fescue

*Note: minimum and maximum based on a combined five samples with a random selection of 60 florets and nine caryopses in normal range of this species using image measurement protocol (ISMA 2020). CDA-S-23411, CDA-S-23396, CDA-S-23410, CDA-S-23387, CDA-S-57406.

 

Festuca trachyphylla (Hack.) R. P. Murray

[Festuca brevipila R. Tracey used by CFIA 2021 and F. trachyphylla (Hack.) Krajina used by USDA-FSA 2022]

Hard fescue

*Note: minimum and maximum sizes are based on 10 florets and five caryopses in a normal range of this species using image measurement protocol (ISMA 2020). CDA-S-23326, CDA-S-57398.

 

Comparison Table of Similar Species

Character	F. ovina	F. rubra subsp. rubra	F. rubra subsp. commutata	F. filiformis	F. heterophylla	F. trachyphylla
Floret length (mm)*	4.0 – 5.7	3.4 – 7.7	4.0 – 6.6	2.2 – 3.7	4.1 – 6.3	3.6 – 4.9
Floret width (mm)*	0.7 – 1.1	0.7 – 1.3	0.7 – 1.1	0.6 – 0.9	0.8 – 1.0	0.8 – 1.0
Lemma awn length (mm)*	1.0 – 4.0	0.3 – 2.9	0.4 – 2.4	Unawned or very short awn, 0.1 – 0.7	0.6 – 2.9	0.7 – 2.4
Lemma surface texture	Lemma mostly smooth or with short stiff hairs near tip or sometimes hairy in upper two-thirds.	Lemma smooth or covered with short stiff or soft hairs especially in upper half.	Lemma smooth or sparsely hairy.	Lemma usually smooth or with short stiff or soft hairs near tip and along margins.	Lemma usually smooth, sometimes with short hairs near tip or long hairy in the upper two-thirds.	Lemma usually smooth or with short stiff hairs in upper half, rarely hairy all over.
Callus	Thick ridge, blunt base.	Blunt with a thick rounded ridge on the lemma side.	Blunt with a thick rounded ridge on the lemma side.	Thin ridge, thicker in the center and appearing slightly curved.	Plump ridge, thicker in the center and appearing slightly curved.	Thick ridge.
Rachilla	Rachilla smooth to sparsely long hairy.	Rachilla smooth or covered with short hairs.	Rachilla smooth or covered with short hairs.	Rachilla smooth or hairy.	Rachilla smooth or sparsely long hairy.	Rachilla smooth to sparsely long hairy.
Palea	Palea surface granular, area between palea keels hairy near tip; keel hairs (palea teeth) along upper one-third of keels short and stiff.	Palea surface granular, tuft of short soft hairs near tip; keel hairs (palea teeth) short and stiff.	Palea surface granular, tuft of short soft hairs near tip; keel hairs (palea teeth) short and stiff.	Palea surface granular, area between the palea keels smooth or with short hairs near the tip; keel hairs (palea teeth) lacking or short and widely spaced.	Palea surface granular, area between palea keels hairy near tip; keel hairs (palea teeth) along upper two-thirds of keels short and stiff and widely spaced.	Palea surface granular, area between palea keels sparsely hairy in upper third and especially near tip.
Caryopsis length (mm)*	2.1 – 3.1	2.9 – 4.1	2.4 – 3.8	1.6 – 1.9	2.9	2.5 – 3.8
Caryopsis width (mm)*	0.5 – 0.7	0.8 – 1.0	0.6 – 1.0	0.7 – 0.8	0.6	0.8 – 0.9
Caryopsis apex	Caryopsis apex not hairy.	Caryopsis apex not hairy.	Caryopsis apex not hairy.	Caryopsis apex not hairy.	Caryopsis apex hairy.	Caryopsis apex not hairy.
Caryopsis other features	Hilum linear, about ¾ the length of caryopsis.	Hilum linear, about ¾ the length of caryopsis.	Hilum linear, about ¾ the length of caryopsis.	Hilum linear, about 4/5 the length of caryopsis.	Hilum linear, about ¾ the length of caryopsis.	Hilum linear, about ¾ the length of caryopsis.

*Note: minimum and maximum measurement of structures in a normal range of these species using image measurement protocol (ISMA 2020).