Foraging
-a primer by professor IMNVS
The things you find around the map? That's called foraging. In spring that's wild horseradish, daffodils, leeks and dandelions. You want to save at least 1 of each of these. In summer you'll find different things: spice berries, grapes and sweet peas. Again, save at least 1 of each. You'll want them for the CC too. Fall? Wild plums, hazelnuts and blackberries. Again, save 1 of each. Winter? Crystal fruit, crocus and holly... save 1 of each except the holly which is only good for selling. The crystal fruit and crocus, save at least 1... and dig with your hoe wherever you see the little wiggly things sticking out of the ground in order to get winter roots and snow yams, because these you'll want to save at least 1 of each for the CC as well.
After that? It's fair game on all of that stuff. Eat it if you need to, sure, if you can't find something better... but a few of those are used in cooking so I'd avoid using them as food now if you can help it. Horseradish, leeks, dandelions, blackberries, wild plums and winter roots are all used in cooking, so if you can avoid eating those, I'd recommend it.
However, of special note... salmonberries and blackberries, they can be found en masse for a few days a year each of them. The salmonberries from Spring 15-18 and the blackberries from Fall 8-11. A lot of the bushes (found all over including on the farm, in town, the backwoods, the bus stop, the cindersap, the secret woods and the mountains... and I hope I didn't miss any locations) will be seen to have berries on them during these times... shake the bush and get berries! Lots and lots of berries! Some folk will eat food that gives them a boost to forage because a higher forage skill means more berries found on each bush. You find 1 berry automatically and you find an additional berry for every 4 levels of forage you have. At forage 12, which can only be attained with buffs, this means 4 berries per bush. In year 2 you can rake in HUNDREDS of berries in a day if you really wanted to and worked for it. Once you're capable of pulling in blackberries by the hundreds for a few days, you probably don't need to keep avoiding eating them because you'll still have plenty for cooking a blackberry cobbler or so when you want to.
I'll note that I'm a hoarder. What I gather in foraging and the crops I grow, if I can use them as ingredients for cooking or crafting, or if they are easy gifts for people? I save that stuff. I try to avoid selling anything that isn't processed. Early on, especially when inexperienced, this may not be the way to go... but I could still recommend holding on to just about 1 of everything you find... just in case, unless you've already found out there is literally no use for it (like holly).