Oddly, this is the one word that uses the on'yomi reading, which you didn't learn with the kanji. To remember this particular swamp, note how there are two kanji in here that make this area particularly swampy. Because it's the swampiest, boggiest place in all of Japan, of course the Shogun (しょう) wants it for himself. Even though it's useless land, he wants the best of everything, being the Shogun and all.
This plant with yellow flowers lives in swamps.