YA (i think) novel about a boy who falls in love with a goddess/witch

So i read this book years and years ago, been trying to find it but with no success. Here's what i remember:

There's a witch/woman/goddess who ages with the seasons. She seduces a young man who goes to live in the woods with her. He is rescued by his friends (i think).

Not much to go on but if anyone can help it'd be much appreciated!
Meredith Ann Pierce's Treasure at the Heart of the Tanglewood? Main character is the goddess/embodiment of the seasons (though unaware of it), so e.g. her hair grows grain during the summer. She doesn't seduce the male lead though - she rescues him.