Lobelia sessilifolia; a species of lobelia
A perennial herb native to East Asia, with blue-purple flowers. Botanical name Lobelia sessilifolia.
I found a colony of Lobelia sessilifolia growing in the marsh.
Katakana spelling is standard for this plant name; usually written in kana.
Kanji form is rare; the plant is almost always written in katakana.
The name サワギキョウ (sawagikyō) literally means 'marsh bellflower', from 沢 (sawa, 'marsh') and 桔梗 (kikyō, 'bellflower'), referring to its habitat and flower shape.