The fruits of many hardwood trees have four layers: an outer skin, a soft layer rich in sugars, a hard shell, and a seed. When we eat the soft layer, we call it a fruit. When we eat the seed we call it a nut.
One of the finest Canadian nuts is the black walnut. Here it is, growing on a tree, cut open to show the four layers, and the nut shell:
We don't eat the soft layer of ripe walnuts because it stains our skin brown and we can't wash it off. However, immature black walnuts, hull included, make excellent pickles. Black walnuts are mostly prized for making fine ice cream, and for topping sugar pies, cakes and rolls. They were widely planted by the First Peoples. One of the largest nut plantations in the world was planted by the Mohawk near Caledon Ontario well before the arrival of European immigrants.
The sugar-rich layer of a fruit encourages wildlife to eat it whole, then defecate the seed far away from the original tree, where it can grow. However, it is not clear what would eat whole a fruit as large as a black walnut. The only known source of dissemination of black walnut seed is grey squirrels, who bury nuts for future food and miss some.
Shagbark hickory was the most valued nut of the First Peoples. It has almost no soft layer. The skin splits easily into 4 segments as soon as the seed is ripe. However, it only bears well at 3-5 year intervals, and is very slow growing.
American chestnut is another fine nut, although rarely found today because a fungus kills most trees. It has no soft layer. It's outer skin has such sharp spines that squirrels can't eat it until the seeds are mature and the outer skin cracks open naturally. Then, any nuts that squirrels bury and don't find until spring grow into new chestnut trees.
Chestnuts were traditionally roasted and eaten as a snack.
White oak is another kind of nut. It's outer layers are incomplete, and cover less than half the shell, so we call it an acorn.
Acorns are a valuable source of food for our wildlife, especially jays and squirrels. The acorns of white oaks were ground to make flour by our indigenous peoples, but are rarely used today. The acorns of red oaks are too bitter for our taste, but squirrels don't mind.
The nuts of conifer trees grow in cones.
Pine nuts are valued raw, for salads and granolas.
Our native nuts take time and effort to collect and prepare for eating. Most nuts that you buy in stores are from tropical species that grow where labour is very cheap, and from varieties that are selected and hybridized to minimize the cost of collection and processing.