For the amateur wild mushroom hunter, an illustrated Field Guide to Edible Mushrooms may not be adequate protection against falsely identifying poisonous fungi as safe for human consumption. There are a few very poisonous mushrooms that account for almost all of the poisoning deaths from mushrooms in the United States, and a couple of them are misleadingly similar to edible mushrooms. Beware.
Instead, the best way to learn to identify edible mushrooms is to accompany an expert out into the field and enlist his or her help with the process. An expert will train fellow mushroom hunters regarding the best seasons to search (during the spring and fall when weather is warm and rainy), where to look (near shady trees in forests is usually a good place to start), and what to look for (or what to avoid).
Can the amateur collect edible mushrooms? Of course. However, it is a very good idea to collect those mushrooms in separate sacks or boxes at first, including notes about where they were found, whether they grew singly or in a group, and any notes about distinctive features that are noted while the mushrooms are harvested. It is important to collect the entire mushroom, including its base, as the information received may lend clues about the mushroom's edibility.
How to identify an edible mushroom
Many mushrooms can be identified using a spore print. To make a spore print, one cuts the mushroom cap off of the base, and leaves the cap on a piece of white or black paper, then covers the mushroom with a jar. If it is at the appropriate age, it will soon shed spores onto the paper that are useful in identification. The color of the spores is especially helpful. A spore print will be visible within one to twelve hours, and can be used to identify the type of mushroom.
It may be useful to begin mushroom hunting with a search for a few very distinctive varieties that are readily identified.
Puffballs (lycoperdon spp. and calvatia spp.) are round or pear-shaped mushrooms that are white, tan, or grey. When they are cut open from top to bottom, they should reveal a completely white interior, like a slice of white bread. There should be no sign of a developing mushroom with gills, stalk, or cap, which would indicate that the mushroom is an amanita (poisonous).
A shaggy mane mushroom is so distinctive that with only a little practice it can be readily identified. The gills of this mushroom are whitish and fragile. As the shaggy mane top deteriorates, it leaves an oily black rim along the bottom of the cap which is most distinctive. These mushrooms are appropriately part of a group of edible mushrooms called the inky caps.
Morels are a delicious and easily-identified mushroom, making them a popular find among mushroom hunters. There are several varieties (one should check the internet or a reliable field guide for illustrated examples), but all have definite pits and ridges over their caps. Caution: some morels are known to be mildly poisonous when consumed with alcohol.
Chanterelles are funnel-shaped and are becoming increasingly popular in the United States. Most are bright orange or yellow. It is important to look under the caps for a distinctive, criss-crossing ridge that indicates that the mushroom is indeed a chanterelle, and edible.
Boletes are considered a good starter mushroom for new mushroom hunters because they are fairly easy to identify, with brownish or reddish-brown caps and a spongy layer of pores rather than gills on the underside of the cap. The King Bolete is probably the most edible of the boletes.
There are other edible varieties of mushrooms to be found in wild forests and fields of north America, but it is best to start off slow and learn to identify a few species that are edible in order to avoid dangerous mistakes. If there is any doubt, a local agricultural station or university can usually help identify mushroom specimens.