Sacred Grove - Piece of Heart Location

There's only a single piece of heart for you to obtain in the Sacred Grove. It's found by destroying the boulder in the center of the large room at the end of the Sacred Woods where you fight the skull kid. You won't be able to get this piece of heart until you've obtained the Shadow Crystal which lets you transform to and from Wolf Form with the press of a button.

In the two screen shots below you'll see the boulder that you have to destroy as well as the location that you'll need to dig in order to uncover the cave that leads to this piece of heart.

After you place a bomb near the boulder and destroy it, you'll not only uncover the hole that leads to this piece of heart you'll also force Poe (#12) to come out from underneath the boulder. Defeat him, capture his soul and make your way inside the cave.

Once you make it inside of the cave you'll need to defeat all of the enemies in order to get the chest to appear. You'll need to use your Bow & Arrows or the Gale Boomerang to attack the enemies that are out of your reach. All in all this piece of heart is pretty easy to get.