Global description
Pycreus macrostachyos is an annual sedge, erect, more or less tufted, 30 to 75 cm high. The stems are relatively robust, trigonal, leafy at the base. The radical leaves are flat or folded, reaching up to 40 cm long and 3 to 6 mm wide. The inflorescence is umbel consisting of 6 to 10 very unequal flower stalk, reaching 10 to 20 cm long, formed of 4-6 loose clusters of spikes, 2 to 3 cm long. It is sub-tended by 4-8 developed leafy bracts, similar in form to that of the leaves but of variable length reaching up to 30 to 40 cm. The lanceolate spikelets are prostrate, measuring 5 to 20 mm long and 2 to 2.5 mm wide.
First leaves
First leaves are short with more or less rolled aestivation.
General habit
Fairly robust, annual plant, reaching up to 1 m in height.
Underground system
Fibrous filiform roots
Stem
Robust stem, reaching 1m high. It is trigonal in section, with clearly marked angles. It is full, glabrous, smooth, leafy only at the base.
Leaf
The leaves are few, simple alternate, arranged in a tristichous way, mainly radical. The lamina is developed, flat or folded, reaching up to 30 or 40 cm long and 3 to 6 mm wide. The surfaces are glabrous and the margin is entire.
Inflorescence
Big, prostrate and diffuse inflorescence, in composite umbel, sub-tended by leaf bracts that reach 40 cm long.
Spikelet
The spikelet is linear-lanceolate, yellow-green color. The glumes have a white membranous margin and a large rounded green keel. Style is bifidus.
Fruit
The fruit is a black biconvex achene, oblong asymmetrical, not zoned transversely, 1.5 mm long and 0.7 mm wide, matching 3/4 of the glume. At maturity, the achene becomes visible due to the increase of the axis of the spike and the opening of the glumes.