Perhaps this is why I always find gardening such hard work. Seems like every time I determine the perfect spot for a plant, the subsequent hole-digging inevitably produces a rock that needs to be moved. Often the rocks, while troublesome, are more of an inconvenience than a true difficulty.
But every once in a while I hit a whopper.
Having finally found a Rusty Blackhaw (Viburnum rufidulum), I had already picked the spot where it could grow up as an understory tree - filling in an opening in my existing tree canopy.
However, a little over two foot deep, I ran into a solid layer of limestone. In my usual planting technique, I started expanding the hole to find an edge so that I could get a rock bar in there and pry out the offending stone. But in this case, the hole quickly widened out to four foot. And once an edge was found, the stone wouldn't even budge.
After a few hours of additional digging, hole-widening and judicious leverage, along with quick placement of rocks under the stone (to prevent it from falling back flat), I was finally able to partially flip it over towards the edge of the hole.
At that point, I reached an impasse. The rock was incredibly dense and thicker then most that I have excavated, so it had substantial weight. I was unable to move it up and out of the hole. No amount of leverage, muscle-straining or outright cussing did more than shift it a few inches - from which it would promptly settle right back into its original position.
This led to the purchase of a come-along so that I could attach one end to a nearby tree, then maneuver the strap under and around the large stone. A few minutes of ratcheting and the stone slowly slid up and out of the hole. I eventually moved it a few feet out of the way.
Of course, at that point I discovered a deeper layer of limestone at the bottom of the hole - but now it was really too deep to get any kind of leverage. I decided to use a sledgehammer and the rock bar to break it up as much as possible so that, in time, the tree's roots could force their way on down past this latest obstacle.
At some point, I'll have to move that rock somewhere else in the garden. But for the foreseeable future, it's gonna stay right there...