Avena barbata
(slender oat)

Preferred Common Name

• slender oat

Other Scientific Names

• Avena alba var. barbata Maire & Weiller
• Avena almeriensis Gand.
• Avena barbata subvar. Hirsute (Moench) E. Morren
• Avena deusta Ball
• Avena hoppeana Scheele
• Avena sallentiana Pau
• Avena sativa var. barbata (Pott ex Link) Fiori
• Avena sesquitertia hort. ex Steud.
• Avena strigosa subsp. barbata THELL.
• Avena striqosa subsp. Barbata (Pott ex Link) Thell.

International Common Names

• English: bearded oat
• Spanish: Avena delgada; Avena loca
• French: Avoine a deux barbes; Avoine barbue
• Portuguese: balanco-bravo

Local Common Names

• Austria: bart-Hafer
• Brazil: aveia-barbada; aveia-brava
• Germany: Wilder Hafer
• Italy: Avena a due barbe
• Norway: skjegghavre
• USA: slender oats; slender wildoat

EPPO code

• AVEBA (Avena barbata)

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Avena
•                                 Species: Avena barbata

Avena barbata is a tetraploid grass (2n=28 chromosomes), originally thought to be derived from Avena fatua but is most likely to have arisen independently by polyploidization from the diploid (2n = 14 chromosomes) Avena hirtula-Avena wiestii complex (Garcia et al., 1991; Alicchio et al., 1995; Ladizinksky, 1995; Katsiotis et al. 1997).

A. barbata is an annual grass species, growing 30-60 cm tall, erect, stems erect, glabrous to short-soft-hairy. Leaves alternate; ligules 1-4 mm long, lacerate, auricles absent; sheaths glabrous to pubescent; blades linear, flat, 1-5 mm wide, glabrous to soft-puberulent. Inflorescence an open terminal panicle, 3-10 cm long. Spikelets 20-30 mm long, slightly compressed, composed of 3-8 florets, the glumes linear to narrowly lanceolate, the lower one 5-10 mm long, 1-nerved, the upper one 8-13 mm long, 3-nerved; lemmas 12-17 mm long, lanceolate, 3-5-nerved, the back keeled to rounded, the apex with two lateral teeth 4-5 mm long, the back of the lemma with a bent awn 12-20 mm long. In California, it flowers from March to June, while in Australia it flowers July-October (Arnow, 1987; Hitchcock, 1944; Holmgren and Holmgren, 1977; Munz, 1959; Rocha Afonso, 1980; Wilken, 1993).

A thorough description is given by Clayton et al. (2012) as follows:

Habit

Annual; culms solitary, or caespitose. Culms erect, or geniculately ascending; 30–100 cm long. Culm-nodes glabrous. Lateral branches lacking. Leaf-sheaths pilose. Ligule an eciliate membrane; 1–6 mm long; obtuse. Leaf-blades 6–30 cm long; 2–20 mm wide. Leaf-blade surface glabrous, or pilose; sparsely hairy.

Inflorescence 

Inflorescence a panicle.Panicle open; elliptic; effuse; nodding; 15–30(–50) cm long; 6–12 cm wide. Primary panicle branches 9–18 cm long. Panicle branches smooth, or scaberulous. Spikelets pendulous; solitary. Fertile spikelets pedicelled. Pedicels filiform.

Fertile Spikelets

Spikelets comprising 2–3 fertile florets; with a barren rhachilla extension. Spikelets lanceolate; laterally compressed; 16–26 mm long; breaking up at maturity; disarticulating below each fertile floret. Rhachilla internodes pilose. Floret callus evident; bearded; obtuse. Floret callus hairs 2–3 mm long.

Glumes

Glumes persistent; similar; exceeding apex of florets; thinner than fertile lemma; gaping. Lower glume lanceolate; 16–26 mm long; 1 length of upper glume; membranous; without keels; 5(–7) -veined. Lower glume apex acuminate. Upper glume elliptic; 16–26 mm long; 1.3 length of adjacent fertile lemma; membranous; without keels; 7(–9) -veined. Upper glume apex acuminate.

Florets

Fertile lemma lanceolate; 12–20 mm long; coriaceous; much thinner above; without keel; 9 -veined. Lemma surface scabrous; rough above; pilose; hairy below. Lemma apex dentate; 2 -fid; awned; 3 -awned. Principal lemma awn dorsal; arising 0.5 way up back of lemma; geniculate; 30–60 mm long overall; with twisted column. Lateral lemma awns arising on apex of lobes; 3–12 mm long; shorter than principal. Palea 10–18 mm long. Palea keels ciliolate.
 
Flower

Anthers 3. Ovary pubescent all over.
 
Fruit

Caryopsis with adherent pericarp; sulcate on hilar side; hairy all over. Hilum linear.

A. barbata was unintentionally introduced to Denmark in 1854 but the species is not currently recorded as invasive (Karlsson, 1998; NOBANIS, 2012). It was recorded in Austria in 1954 but its impact and population status are unknown (Essl and Rabitsch, 2002; NOBANIS, 2012). Vasey (1885) first reported the species in California but it had probably become widespread much earlier and is thought to have been introduced into California more than once during the eighteenth century (Robbins, 1940). Studies suggest that nearly all naturalized California strains are most closely related to those found in southwestern Spain (Pérez de la Vega, 1991; Garcia et al., 1989). Cluster and Allard (1995) and Rai (1985) also provided evidence showing that significant ecotypic differentiation may have taken place in California within the last 150-200 generations (perhaps less than 150-200 years).

Soil drainage

• free
• impeded

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• light
• medium

Special soil tolerances

• infertile

Accidental Introduction

A. barbata historically was unintentionally introduced to new areas via contaminated seed mixtures, meant to be of commercial quality oat.

Intentional Introduction

The species has been widely introduced to North America and a number of European countries as a fodder crop.

Impact on Habitats

A. barbata has been found to out-compete native grass and woody species by exhausting the surface soil-water before native species have had a chance to establish (Standish et al., 2008). It has also been found to alter the fire regime of areas of Australia (FloraBase, 2012). Instead of woody species dominating areas, grass species are dominant and much easier to flash fire. 

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Is a habitat generalist
• Pioneering in disturbed areas
• Tolerant of shade
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Modification of fire regime
• Modification of hydrology
• Modification of nutrient regime
• Modification of successional patterns
• Negatively impacts tourism
• Reduced amenity values
• Reduced native biodiversity
• Threat to/ loss of endangered species

• Competition - monopolizing resources
• Competition - shading
• Competition - smothering

Economic Value

The straw of A. barbata can be used for biomass, fibre, mulch, paper-making and thatching (Hill, 1952).

Social Benefit

The seeds of A. barbata are rather small but very edible. The seed ripens in the latter half of the summer and, when harvested and dried, can still be viable after several years of storage. It has a floury texture and a mild, creamy flavor. It can be used as a staple food crop in either savory or sweet dishes. The seed can be cooked whole, though is commonly ground into flour and used as oat (A. sativa) is used, especially as a biscuit, bread or porridge component. The seed can also be sprouted and used raw or cooked in salad. The roasted seed can also be used as a coffee substitute (PFAF, 2012).