If you are someone who regularly goes out foraging for wild mushrooms it will be important that you have the right kind of mushroom knife for when it comes to harvesting your dinner. There is some debate as to the proper way to pick a mushroom, with some people believing that you can just pull the mushroom out of the ground, and some that think the best way is to cut through the stem near the base because they believe that the mushroom will grow back again from the left-over stem. Whilst some mushrooms do have a kind of stem-regrowth ability, it is fairly safe to say that most mushrooms wouldn't re-grow from the stem that they have been cut from. However, you should never pull a mushroom from the ground because this can damage the mycelium network that is running beneath the ground. Always try and cut them from as near to the base as possible.
The mushroom knife that you will use needs to be sharp, in order for the mushroom to be cleanly cut through at the stem without having to hack away or to saw it, which could cause damage to you or your knife. It will also need to be lightweight and easily accessible, long lasting, able to stand most weather (mainly wet as this is when most mushrooms are collected) and needs to be strong too.
Not all mushrooms consist of a small stem which can be easily cut through. Some mushrooms have a much larger stem, and some are often very tough. The beefsteak fungus which grows on trees will probably be quite hard to pick using just a standard knife. Something with a serated edge might be required to remove this type of fungi, so you may find it beneficial to have a knife either with a part serated edge, or to buy yourself a seperate mushroom knife already with a serated edge, thus meaning that you will want to carry both types of knife with you when out picking mushrooms. A decent penknife might be able to do the job adequately, although the blade is usually quite small. Other mushrooms that may require a stronger, more serated blade to cut through would include most types that grow on trees, such as the Chicken Of The Woods and the Hen Of The Woods.
There are some cleverly designed mushroom knives that come with a brush attached to them ready for use after you have cut the mushroom. Some knives have this brush head tucked away in the handle of the knife and this can be quickly accessed if you want to brush away any excess dirt whilst you are still outside and in the mushrooms natural habitat.
A mushroom knife made from a strong, hard wood such as oak or walnut should make a very decent knife which should accompany even the most avid mycologist for the rest of their life, and theoreticcally should be able to provide them and their families with tons of mushrooms to enjoy season after season. A typical mushroom knife will probably cost you about £10.