casual alien

Noun

(botany) A plant that appears with no apparent human assistance but does not develop a sustained population.

Japanese Meaning

人為的な介入なしに自然に現れるが、持続的な個体群を維持しない外来性の植物

The botanist noted a casual alien sprouting along the roadside after the flood.

洪水の後、植物学者は路肩に一時的に現れる外来植物が芽吹いているのを確認した。

Sense（1）

(botany) A plant that appears with no apparent human assistance but does not develop a sustained population.

casual aliens

（ plural ）