Solanum carolinense (Carolina horsenettle, "Warunasubi")

Japanese name: ワルナスビ （悪茄子）
Scientific name: Solanum carolinense

[Overview]
A perennial 50–100 cm tall, found in fields and grassland.
It has long rhizomes and grows profusely.
The stem is erect, much branched, and bends at each node.
The stem is densely covered with stellate hairs, and bears prickles, as do the leaf stalks and the veins on the underside of the leaves.
The leaves are simple and alternate, oblong, 8–15 cm long and 4–8 cm wide, with stellate hairs on both surfaces.
The leaf margin has 3–4 large teeth.
Umbels arise partway up the stem, bearing 6–10 flowers.
The corolla is white to pale purple, 1.8 cm across, and 5-lobed in a star shape.
The fruit is spherical, 1.5 cm across, and ripens yellow.

[History]
Naturalization was confirmed in the Meiji period, and it has spread through warm regions from Honshu southward.

[Notes]
It is designated as an alien species requiring caution under the Invasive Alien Species Act.

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