The things growing all around you that you know nothing about. For example, a long time ago, truffles were mentioned here and Broddie Gibbons wrote from Fair Green, Westport, to say that he and his friends, on the way to school, dug them up at the back of their houses, where they used to play. And they would eat them.
Someone wrote in quickly to say they weren't truffles, they were pig nuts, as everyone should have known. Have you ever seen or eaten a pig nut? Once on TV, BBC, a chap who specialises on living off the land - how to light a fire by rubbing sticks, what to eat from the hedges and so on - pulled up a growing flower or weed in the woods, rubbed off the dirt from the root and chewed it noisily. Said it was good. That was a pig nut or earth nut.
A book just to hand tells us it comes from the family of Umbelliferae, and is conopodium majus. It is perennial and has a tuberous rootstock, growing as large as a chestnut and brown in colour. It may be eaten raw, but is said to be best when boiled, or roasted like a chestnut, which it much resembles. It has a tough, slender stem with few leaves. The leaf is divided into three parts, and each of these is cut up into threadlike portions, but the general outline is broad, wedge shape, on a slender foot stalk. The illustration is black and white and not very much help for an amateur. There are small white flowers in the form of a compound umbel.
Among all the roadside white weeds/flowers of summer, you might have difficulty in distinguishing it. It flowers, apparently throughout the summer. All this information is from a pocket sized The Observer's Book of Wild Flowers, compiled by W. J. Stokoe and published by Frederick Warne and Co. No date.
Remember the rule: if you don't know, ask an expert. Don't experiment. Don't eat anything you are not sure of, whether fungi under ground truffles, or over the ground like the many varieties of mushrooms we have. And, unless you are Broddie Gibbons or some other experienced person, don't try pig nuts or earth nuts. Tempting though it may be. That BBC man crunched away with, apparently, great satisfaction.