Because the nut is a storage tuber for the plant then it is findable all year round (but of course new plants do need to build up the reserves that have been used over winter ) so would probably wait a bit otherwise will more likely be a futile exercise. Often find them easily in ancient or unimproved/not ploughed pastureland/meadowland/turf; or as the following link says amongst bluebells in lightly deciduous wooded areas and edges.
http://www.naturessecretlarder.co.u...pignut-foraging-tutorial-conopodium-majus.htm - as it says beware of eating bluebell tubers, but looks like a scraggy small hazelnut if that helps. peel off the brown skin and eat raw or boil like potato. You really have to follow the delicate stem down gently. then near the bottom of the stem it turns right angles and the nut is at the end of it. So a lot of delicate effort to obtain a pea-sized nut. v. tasty but not much food per plant.
It is easier to find when in flower though (up here in Scotland that's nearer to late May/early July) - a very delicate umbellifer head. Main problem is that it can be confused with other umbellifers (umbrella headed flowers like cow pasley etc) but if the wispy feathery leaves are consistently the same size all the way down the stem then it probably is pignut - finding the nut is the answer!
Have to let you know that with all plants that you need the landowner's permission - in some cases like on protected nature reserves, SSSIs, etc you also need the permission of English Nature, Scottish Natural Heritage etc.
Hope this helps. >C
