Global description
Conyza sumatrensis is an erect herb, hairy, more or less branched. The stem is bristling with stiff white hairs. The leaves are narrow, spearhead shape. They are alternately arranged along the stem. The leaf margin is irregularly dentate. The leaf blade is hairy on both sides, especially at the ribs. The flowers are collected into small spherical heads, whitish and very tight. The heads are arranged in small loose inflorescences at the leaf base up to the top of the plant, forming a large pyramidal inflorescence. The fruit is small, bristling at the top with many white hairs.
Cotyledons
The cotyledons are tiny, 2 to 3 mm long and 1.5 to 2 mm wide, glabrous, quickly deciduous. The leaf blade is rounded, shortly stalked (1 mm).
First leaves
The first leaves are alternate, simple, entire, arranged in rosette, markedly petiolate. The leaf blade is rounded at first, then oval to elliptical. The apex has a foliated apicule . The following leaves are elliptical and then lanceolate, dented to almost lobed, ending into a foliaceous petiole. The leaf blade is covered with dense white long or short hairs, tines or lobes extend by an apicule. Greyish green tint.
General habit
Greyish green plant, erect growth habit. Up to 2 m high.
Underground system
The plant has a taproot system.
Stem
The stem is cylindrical, slightly ribbed, full, robust, erect, sometimes branched from the base. Pubescent and very leafy.
Leaf
The leaves are simple, sessile, alternate, hairy on both sides, especially on the ribs. The base leaves are broad, usually lanceolate, lobed or rarely serrated. 3 to 14 cm long and 0.4 to 2.5 cm wide. Middle leaves narrow, lanceolate slightly or not dentate. Leaves at the top are sub-linear attenuated at both ends. Base of lamina is acute, ending in a petiole. Tip is acute, apiculate. Margin is dentate to lobed. Tines and lobes apiculate.
Inflorescence
The inflorescence is a long terminal pyramida panicle, l composed of small ovoid capitulums of 5 to 8 mm long and 4 mm wide, densely pubescent, cream color. Involucre bracts lanceolate, pubescent.
Flower
External flowers female, on several rows, filiform tubular at base with short bidentate ligule at the top, 4 mm long, yellowish to greenish color. Central flowers bisexual, tubulate 4 to 4,5 mm long, corolla 5-dentate yellowish.
Fruit
The fruit is an ellipsoid achene, 1.2 to 1.5 mm long, slightly pubescent, with 4 ribs. Pappus formed by many whitish to pale brown bristles, 4 to 5 mm long.
