Given all the edible plants we've seen during our short stroll, I'm surprised to hear Seebeck say that wild plants are seldom useful in real survival scenarios. People can almost always live without food until rescuers arrive, he explains; shelter, water, and warmth are much higher priorities, and foraging for edible plants just wastes valuable energy. Plus, even though Colorado has a relative paucity of poisonous plants, there are a few dangerous species that look very similar to edible plants: death camas, poison hemlock, and sweet pea, among them.
And there are other dangers in the city for would-be gatherers. Walking back along the bike path toward REI, we pass an evening primrose, whose roots, leaves, buds, and flowers all are edible, but Seebeck demurs: "It looks like it may have been sprayed. I wouldn't want to eat that." The leaves of urban plants may be covered with herbicides and pollutants from nearby highways; toxins may accumulate in the soils; and you have to worry about giardia on plants that grow in water. It seems to me that even though you may well be able to dine daily on back-alley and roadside plants in Denver, you probably wouldn't want to do it too often—and only then for the sheer novelty of it.
Moreover, Seebeck says, overharvesting wild plants can threaten their survival, especially if foragers pull up entire roots. Pick only a few leaves or berries from a plant; if you're going to eat a lot of wild food, Cattail Bob suggests planting the seeds and growing your own.
In other words, foraging for plants should be a fun pastime, not a way to cut down on your grocery bills. Try a salad of wild greens or serve a novel appetizer at a dinner party. Just remember Cattail Bob's sage advice: "If you're making a dish from wild plants for guests, you have to use as much color, texture, and taste variety as possible. Because remember, you're asking them to eat weeds."