Desmanthus illinoensis (Illinois bundleflower, "Haikusanemu")

Japanese name: ハイクサネム （這草合歓）
Scientific name: Desmanthus illinoensis

[Overview]
A perennial about 1 m tall, found along roadsides and in fields.
The stems branch well, grow obliquely upward, and have ridges.
The leaves are alternate and bipinnate, with 4–12 pairs of pinnae.
The leaflets are 3–4 mm long and set densely in two rows.
Flower stalks extend from the leaf axils and bear white flower heads 1 cm across.
The fruit is an oblong legume 15–25 mm long, which turns blackish brown when ripe.

[History]
Confirmed in Okinawa in 1966, it forms colonies locally and has become a seriously harmful weed.

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