きく
chrysanthemum
kiku
JMdict 1226210
菊(きく)chrysanthemumの花(はな)flowerが咲(さ)いたbloomed
The chrysanthemums bloomed
の (of) links 菊(きく) (chrysanthemum) to 花(はな) (flower) — "the chrysanthemum's flower." が (subject) marks that flower as the subject, and the verb 咲く(さく) (bloom) shifts to plain past 咲いた(さいた) (bloomed), reporting something that just happened.