It may not surprise you to learn that a certain percentage of my diet comes from wild forage foods. Wild forage is a way to add delicious variety to my life and save a bit of my skimpy budget.
At some points in my life (i.e. between employment), wild forage foods have been the primary component of my diet: breakfasts of wild asparagus, wood sorrel, and lamb’s quarters, lunches of wild cherries, dinners of feral apples, chestnuts, and hen of the woods mushrooms.
Not that I recommend this strategy for any starving grad student…you have to be comfortable identifying the plants that you eat, and careful in cleaning them in case they have been sprayed with something awful. You should never eat a mushroom unless you are 100% confident in its identity. My mom had a friend who died of a misidentified mushroom.
Nonetheless, I have a few old stand-bys that I return to year after year, that I would feel comfortable recommending to anyone.
(NB: I’m most experienced at foraging in eastern North America. I have experience in other countries, but am less comfortable providing recommendations.)
Sorted by time of year.
Morels probably come out earliest. They are pretty unmistakable mushies. See my post here for a recipe and a terrible pun.
One of the earliest and best wild forage foods is Wild Asparagus. Wild asparagus is the same species as the cultivated kind, but it has escaped and gone feral! Learn to recognize the fringy adult plant in the fall and you will surely have fresh asparagus for breakfast in early spring.

A fresh young sprig of wild asparagus (Asparagus officionalis).

My best friend diving for asparagus. Get it!

A drawing I did a loooonnnnggg time ago of asparagus, useful because of the adult form.
There are a few weedy species that are around all year that are always good to eat, but are not very substantial. There is the tart, lemony Yellow Wood Sorrel:

Yellow Wood Sorrel (Oxalis stricta)

And there is the velvety smooth Lamb’s Quarters, which tastes rather like spinach. It has a silvery sheen to it.

Adult Lamb’s Quarters (not as good to eat at this age)

I actually kind of like this drawing, even though it is old.
I think all of the Rubus species are good to eat; they have fruits available at different times of year. First, there are black raspberries, then raspberries, blackberries, Japanese Wineberries, and Dewberries. Yum!

As we get later in the summer, the shimmery leaves of the Autumn olive attract my attention. From the berries, you can make a pretty yummy jam or fruit leather.

Then, of course there are blueberries. There are two wild species here: high bush and low bush blueberry, which taste similar. (Huckleberries are very similar and also good to eat!) The high bush blueberries are bigger, though.

They flower early in summer, and fruit in autumn.
Then there are Staghorn Sumac berries, from which you can make a delightful tea that tastes just like cranberry juice.

And soon thereafter, the wild Black Cherries:

The Chinese chestnuts produce abundant food, but you have to fight the squirrels for the nuts.

And finally, the wild apples of old orchards (my favourite!). Even if you have to fight the horses for them. I like to climb into the top of the tree to grab the ones the horses can’t reach.

Explore at your own risk! The rewards can be great, but make sure you know the species you are eating.