Cyperus esculentus (chufa sedge, "Shokuyogayatsuri")

Japanese name: ショクヨウガヤツリ （食用蚊帳吊）
Scientific name: Cyperus esculentus

[Overview]
A perennial 0.3–1.2 m tall, found from roadsides to paddy fields as long as the site is sunny.
It extends underground stems that bear tubers 0.3–1.9 cm in diameter.
A single plant can have as many as 600 tubers.
The stem is usually less than 1 cm in diameter and triangular in cross section.
The leaves are linear, 0.3–1 cm wide, and often longer than the stem.
At the stem tip it extends 4–7 branches in an umbel-like arrangement, and spike-like florets emerge at the branch tips, bearing many spikelets.
Long leaf-like bracts are attached to the inflorescence.
The spikelets are yellowish brown or straw-colored, linear, about 1–4 cm long and 0.2 cm wide.
The fruit is about 0.1 cm long, obovate with 3 ridges, and grayish brown.
It resembles Hama-suge and Mizu-gayatsuri, but can be distinguished from Hama-suge by the color of the spikelets and by the absence of tubers partway along the rhizome, and from Mizu-gayatsuri by its round, small tubers.

[History]
There are records of its cultivation in ancient Egypt.
In Japan it was confirmed around 1980 in the Nasu region of Tochigi, and it has been confirmed as naturalized from southern Tohoku southward.

[Uses]
The tubers, also called tiger nuts, are eaten.

[Notes]
The form whose tubers are eaten is regarded as the cultivated type (Shokuyo-gayatsuri), and the form that has become a weed is regarded as the weedy type (Ki-hamasuge).

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