They’re dead man’s fingers.
They may look like fingers rising from the earth, but they’re actually fungus. And they’re commonly called “Dead man’s fingers.”
They sometimes grow separately, and sometimes they grow in a bunch, like in this picture, resembling fingers.
Xylaria polymorpha is the botanical name, and they usually grow from the bases of rotting or injured tree stumps and decaying wood.
They are common inhabitants of forest and woodland areas. They can be found in Britain and Ireland, and also throughout mainland Europe and in many parts of North America.
They belong to the family of the morel and the truffle, but these ones aren’t edible.
They are black or brown on the outside -occasionally shades of blue/green- and they are incredibly white on the inside.
Towards the end of their lifespan, they look like what your dog would leave in the backyard.