The major rule of thumb in foraging is never take more than a third of a patch of the plant, mushroom, lichen, moss, etc from a patch. This allows the plant or organism to still survive and it also allows for others to enjoy the bounty of that patch too.
It is also about weighing up your own wants and the plants needs in order to survive. In our modern world we don’t forage to survive, we have many other sources of food available to us.
Foraging is about maintaining a balance with the natural world, so that we can benefit from Gathering Nature in a healthy and safe way, whilst protecting the plants and fungi that are vital to our ecosystems.