noun
A night-blooming morning glory species; the name literally means 'night face'.
庭にヨルガオが咲いている。
Moonflowers are blooming in the garden.
ヨルガオは夕方から花を開く。
Moonflowers open their blossoms in the evening.
Compound of 夜 (よる, 'night') and 顔 (かお, 'face'), referring to the flower's night-blooming habit. The reading よるがお is a straightforward combination of the two elements.