When I was little, we gathered blackberries from an empty lot in the neighborhood before it got built up. But I think most Americans don't really get into gathering stuff from the wild. We're a culture extremely preoccupied with food safety issues and cleanliness, and the idea of just picking up something from the ground and eating it is very unappealing. The Japanese are more open about that sort of thing. Groups of friends or families often go on mushroom-hunting or 山菜 (sansai: mountain veggies) gathering trips at the appropriate seasons. One of the reasons 'organic' hasn't taken off in such a big way in Japan is because the Japanese already see it as self-evident that wild, uncultivated or at least barely touched ingredients are best, and don't feel they need to label something so obvious. While I don't do a lot of food-gathering in the Tokyo streets, I had a pleasant experience when I went back to my old home in Ibaraki Prefecture north of Tokyo. Fall was already well under way, and while dirt biking we pass some chestnut trees. 
We got off our bikes, stuffed them in our bags (those spines go through bike gloves), and I soaked them overnight and spent the next afternoon peeling them. We made 栗ご飯 (kuri gohan; chestnut rice) for a BBQ the next day. The aroma was incredible, it blew store-bought chestnuts out of the water. Though they were tiny compared to the cultivated version:
栗ご飯 作り方:
栗ー いっぱい（むいたもの）
米ー ３カップ
だし汁ー ９００cc
薄口醤油ー４０cc
みりんー １５cc（必要ではない）
塩ー 小さじ１/２
酒ー ３０cc
１. 米は洗ってざるに上げ、３０分おく。
２. 栗は半分か４分の１に切る。
３. だしに薄口醤油、みりん、塩をあわせ、かき混ぜて塩を溶かす。
４. ご飯用の鍋に洗い米３.の調味しただしじる、栗を入れて炊く。
５. 炊き上がったら酒をふり、１０分を待つ。
Chestnut Rice Recipe:
Chestnuts-As many as possible (peeled)
Rice (short-grained)- 3 cups
Dashi Stock- 900 cc
Usukuchi Soy Sauce (regular works fine too)- 40 cc
Mirin- 15 cc (optional)
Salt- 1/2 teaspoon
Sake- 30 cc
1. Wash the rice and let it sit 30 minutes in a colander.
2. Cut the chestnuts into halves or quarters depending on size.
3. Mix the dashi with the soy, mirin, and salt until it dissolves.
4. Mix the rice with the seasoned dashi from Step 3, add chestnuts, and cook.
5. When done cooking, sprinkle the sake on top and let sit 10 minutes before eating.
