Digitaria bicornis (Lam.) Roem. & Schult.

Code

DIGBC

Growth form

Grass

Life cycle

Annual

Habitat

Terrestrial

Global description

Digitaria bicornis is a stout annual grass, up to 1 m tall, with glaucous green leaves, glabrous sheath, or stiff, milky-based, tubercle-like hairs, up to 15 cm long, also with hair. based on tuberculosis. The ligule is 4 mm tall; the inflorescence is digitally formed from 3 to 9 racemes obliquely erect up to 20 cm long, rigid axis of silvery appearance, a little glossy, geminal spikelets about 4 mm long are different from each other: spikelet pedicellate very hairy (bristly with hair), the sessile spikelet appearing glabrous.

General habit

Digitaria bicornis is an annual grass in loose tuft, erect, robust (compared to other crabgrass in the region) up to 1 m in height.

Underground system

Fasciculate roots at the base of the plant, and presence of adventitious roots at the lower nodes of the culms in contact with the soil.

Culm

The culm is cylindrical, hollow, geniculate ascending, up to 30 to 100 cm long, sometimes rooted at the lower nodes. The knots are glabrous.

Leaf

The leaves are simple alternate, usually of a glaucous green color. The sheath is glabrous or pubescent, with stiff, tubercle-like silks at the base. The ligule is truncated membranous, large, 2.5-4 mm high. The blade is linear from 3 to 15 cm long and 4 to 8 mm wide. It is flat, margin often wavy to tense. The two faces are most often provided with tubercle hairs at the base.

Inflorescence

The inflorescence is digitalised, consisting of 3 to 9 obliquely erect linear racemes, varying in length from 4 to 20 cm, with a somewhat wavy rigid axis, 0.7 to 1 mm wide, pale green, silvery, slightly shiny because of the hairiness of the spikelets. The spikelets are associated in pairs, one is pedicelled (pedicel 2 mm), the other is sub-sessile.

Spikelet

The spikelets are lanceolate, acute, 3 to 4 mm long, appressed against the axis. The spikelet is more hairy than the spikelet subsessile and has a fringe of shaggy hairs that bristle along the margin at maturity. The subsessile spikelet is glabrous or subglabrous. The lower glume is reduced to a scale. The upper glume reaches 2/3 or 3/4 of the length of the spikelet, it is tri-nerved and pilose on the margin and between the ribs. The hairs are first appressed and spread out at maturity for the pedicel spikelet. The lower flower is empty, the lemma is the size of the spikelet, 7-veined, almost glabrous for the sessile spikelet, very hairy especially on the margin for the spikelet pedicel. The upper flower is fertile lanceolate, acute, a little shorter than the spikelet, with yellow cartilaginous lemmas.

Grain

The fruit is a grain (caryopsis).

Digitaria bicornis is an annual plant. It reproduces only by seeds.

Distinctive characters between Digitaria horizontalis, D. ciliaris and D. bicornis in Madagascar

In addition to the size of the ligule, which is considerably more developed for Digitaria bicornis, the first two species, D. horizontalis and D. ciliaris, are relatively early species in the season, with a short cycle, they have a relatively small size (up to 60 or 80 cm), with subdigitated inflorescences of very variable number of digitized racems, 4 to 15 cm long, while D. bicornis is more robust, up to 1 m tall, growing later in the season, with a longer cycle. Leaves are somewhat glaucous green, with a glabrous sheath or with stiff, stiff hairs on a tuberculous base, with a leaf blade up to 15 cm long, also bearing tuberculous hairs (J. Bosser, 1969); The inflorescence is digitized, consisting of 3 to 9 obliquely upright  linear racems up to 20 cm long, rigid axis of silvered appearance, somewhat shiny, the twin spikelets (like those of the other two species) about 4 mm long are different: the pedicelated spikelet is very hairy (bristling with hair) while the sessile spikelet appears glabrous (J. Bosser, 1969).
In Madagascar, D. horizontalis grows throughout the agro-ecological zones, D. ciliaris grows in the more humid areas, especially on the Uplands and the Eastern Coast, while D. bicornis is a weed of drier stations ( J. Bosser, 1969) in the South, South-West, Middle-West and North-West. In the Middle West (rainfall 1300 to 1500 mm) the 3 species can coexist in the same field.

Ruderal and weed species on sandy soils, from the littoral to 2000 m of altitude.

Madagascar: Digitaria bicornis is a weed of dry and sunny sites, present in the South (sub-climate), South-West, the Middle-West and North-West (subhumid climate). It develops on alluvium, sandy ferruginous soils (red sands). It can be quite abundant in summerfallow.

Worldwide distribution

Digitaria bicornis is a species of tropical regions. It is present in India, China, Malaysia, Indonesia, Myanmar, New Guinea, Sri Lanka, Thailand, Australia, Africa, Madagascar, Comoros, Mascareignes, Arabia. It was introduced to America.

 

Herbarium pictures ReCOLNAT: https://explore.recolnat.org/search/botanique/simplequery=Digitaria%2520bicornis