While this tree is not a willow at all, the many trunks growing in a tangle of limbs will remind any Potterhead of it's namesake as soon as they set eyes on it. The limbs scatter in such a way that they look ready to strike out at any moment, just like it's namesake. This pine tree stands alone in a small clearing along one of the well-marked paths, and it is easily distinguishable from the rest of the wood. Do not attempt by light of full moon, and be on the lookout for werewolves.
Start your trek by heading up Adams Road in Greenfield, and follow it as it turns into Lampblack Road. Parking for the Griswold Conservation Area is on the left, marked by a large red-and-black sign. Donated to the town of Greenfield by The Griswold Family and Greenfield Tap and Die, the area is 200 acres of public land designed to be maintained by funds collected from periodic harvesting (for maintenence purposes) and the land is fill of wildflowers, raptors, ferns, and any number of tree species. It feels very wild. Pick up one of the free Stewardship Trail Maps that lead you through the two-mile long trail with numbered landmarks for educational stops.
Alternatively, you can download the map as a PDF, here.
For the cacher in a hurry, the best and easiest way to reach the cache is to follow the trail, marked by yellow and blue diamonds until Stop 12. The tree and the cache are located beyond 12, but before the curve of the trail.
You're looking for a small, camo'd lock-and-lock container. It isn't hidden on the tree itself, because I wanted to preserve as much environment as I could in a conservatory. It is within sight of the trail, and direct sight of the tree, so if you lose either you have gone too far.