Yes, DAYLILY is a Scrabble word!

Letter values in Scrabble US: D 2, A 1, Y 4, L 1, I 1, L 1, Y 4.

Is it a valid word?

DAYLILY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of numerous perennials having tuberous roots and long narrow bladelike leaves and usually yellow lily-like flowers that bloom for only a day

Also: day lily.