For small seedlings that have stems too small to grab with your hand, try using a pair of channel-lock pliers. They are adjustable, so you can grab a long section of stem with the teeth. Use gentle tugs to loosen before pulling out of the soil.
For larger diameter stems, there is a weed wrench. The original manufacturer of the “Weed Wrench” closed shop many years ago, but there are several manufacturers of very similar tools on the market today. The brand of the one I chose comes in several sizes that vary in pulling power. I purchased one that will pull up to two-inch diameter trees. The long handle, the fulcrum plate, which allows for an attachment of a board in case of soft soils, and the fact that the jaws grab the stem at the soil line gives it great pulling action. Watch the weed wrench in action.
It will also pull up smaller diameter trees, but anything less than ½ inches may get sheared off by the jaws with a forceful pull. Gentle tugs work best with small stems.
So instead of trying to dig up an oak tree that has come up under a shrub, or worse yet, pruning it to the ground to only have it respond by growing several new stems, try one of these simple tools – you will be amazed!