Oh ye of little faith -
Crabgrass (Goose Grass)
11% Protein
29% Fiber
7% Carbs
0.5% Calcium, 0.26% Phosphorus, good potassium source
Quackgrass references an article evaluating its use as forage for sheep, now unavailable. But with the title, the article can be found here. Full text here...
Couldn't tell you. I don't have a green thumb. Nor are our growing zones even remotely similar. Yes, that's a rather small area to work - but anything is better than nothing.
At the risk of outing one of my secrets, I find this source remarkably useful. Sometimes, you need to hunt a bit, but all the common, most of the uncommon, and a decent amount of the truly obscure is gathered here, nutrition wise. Unfortunately, its not all presented in the same way, so...