My backyard is full of dandelions and other various weeds—please come by and have a field day!!! ;-)
This is a topic I could write about at some length. There are a tremendous number of edible wild plants. Fifteen years ago when I was out of work and going through a divorce, I had about $10 left every month for groceries, so I supplanted my menu with pond fish and wild plants.
There is a big difference between ‘edible’ and ‘nutritious’. Things like dandelions and purslane are fine salad greens, vitamin rich, but have few calories. Some of my favorites are:
One of the best greens is lambsquarters, which is tasty, and does not get tough in hot summer weather like most other greens do. The seeds are nutrient rich as well.
Dandelion flowers should be considered a food source, as well. The pollen-rich flowers have more nutrients and calories than the leaves. You can use them in stir-fries, or as a generic vegetable filler in breads, meat-loafs, etc.
Sassafras leaves can be dried and powdered, and used as a thickening agent in stews.
Acorns are very nutritious, full of fat, carbs and protein. They also have a lot of tannic acid, so they must be crushed and soaked for some days before consumption. Ground, they can be mixed with flour in breads and biscuits.
Walnuts and hickory nuts. A bit labor intensive to open, but very calorie-rich.
Cat-tails are tremendously useful. The tuberous roots are starchy, and the catkin pollen is a good flour substitute.
Blackberries, blueberries, mulberries, raspberries, serviceberries, strawberries, sumac berries, elderberries, rose hips, ground cherries. ‘Nuff said. Not every wild berry is edible, some are poisonous, make a positive ID before you eat.
The inner bark on some trees is edible. Hickory, poplar, birch, and white pine are a couple. In winter, this may be the only food source you can find.
Any grass seed is edible. Foxtail grows anywhere. It’s very high fiber, but can provide starches.
Day Lily roots - related to the onion. Not every lily root is edible, wait until the bloom to make a positive ID.
Wild asparagus - a good springtime veg.
THe problem with wild plants as a food source is that they are pretty calorie-poor They are a good vitamin source, but hard to get enough calories from them. They can supplement salads, stir-fries and stews, but you really need a primary calorie source.
In an survival situation, look for unconventional sources. Pumpkins are something often overlooked. On November 1st, you can get all you want for free. The pumpkin meat is very nutritious, and the seeds rich in fat and protein. You can thin-slice the flesh and dry it to preserve it.
Plain old corn is great. If you live near a corn field you can forage a quick meal in an emergency (I do not advocate theft!) THe young ears can be eaten whole when the kernals are just forming. The stalks are full of sugar-rich sap. Dried field corn can be roasted in oil, where it pops somewhat like popcorn. Salted, it is a great snack. You can make hominy from corn by boiiling it with wood-ashes. THis loosens the hull, and converts the amino acids to make it more nutritious.
There is also a lot of wild game, although hunting in an urban or suburban environment is not always appreciated!
Read up on the American Indians. They were better nourished than the Europeans of the day, and they really knew what they were doing.