From Wiktionary, the free dictionary
From 昼顔 (hirugao, “bindweed, Calystegia”) + 科 (-ka, “taxonomic family”).
ヒルガオ科 • (hirugaoka)
- Convolvulaceae, a family of herbaceous plants; bindweeds, morning glories
- Hyponyms: 昼顔 (hirugao), 朝顔 (asagao), 薩摩芋 (Satsuma imo)