I think it was a retelling of Norse myths, something about an apple tree and a girl who reminded me of Clarisse La Rue from the The Percy Jackson and the Olympians series. Jack was the main character, and there was something about hobgoblins and a girl named Hazel (or something like that.)
Help is appreciated! Thanks in advance.

Andalee, is it The Land of the Silver Apples by Nancy Farmer?

Summary:
Jack is amazed to have caused an earthquake. He is thirteen, after all, and only a bard-in-training. But his sister, Lucy, has been stolen by the Lady of the Lake; stolen a second time in her young life, as he learns to his terror. Caught between belief in the old gods and Christianity (790 AD, Britain), Jack calls upon his ash wood staff to subdue a passel of unruly monks, and, for his daring, ends up in a knucker hole. It is unforgettable -- for the boy and for readers -- as are the magical reappearance of the berserker Thorgil from a burial by moss; new characters Pega, a slave girl from Jack's village, and the eager-to-marry-her Bugaboo (a hobgoblin king); kelpies; yarthkins; and elves (not the enchanted sprites one would expect but the fallen angels of legend). Rarely does a sequel enlarge so brilliantly the world of the first story.

Yes! That is it! Actually, looking at it now, I must have smooshed together both books in my mind... Thanks!

Yay, you're welcome!