Wood sorrel and ‘the other’ sorrel (Arorow Sorrel / Sheep Sorrel / Meadow Sorrel / Field Sorrel – whatever!) both have fantastic lemony flavoured leaves.
Wood sorrel is easy to identify (if you can find it this early and perhaps it is a little too sparse to be picked yet)
The other ‘field’ sorrels are more difficult to identify before their flower stalks appears, they look a bit like small docks.
Wonderful added to those early salads, or try a small bunch torn (better than chopped) into strips stirred into an omelette or used to stuff salmon of trout.