I need to dig some holes in soft wet clay soil with lots of small tree roots in it. I've got a variety of spades, including a heavy narrow one for digging drains, but the roots make it very difficult to make progress. When I hit the roots with a spade they sink into the soil rather than cutting cleanly.
What's the best way of dealing with roots? Is there a special kind of spade that will cut through them easily? Should I sharpen the edge of a spade with an angle grinder?