Beneficial "weed" mix for Colorado

I am trying to come up with a mix of seeds to broadcast over sheet mulch beds. These will have large vegetable plants in them, like squash or tomato. However, there is definitely a niche for "weeds." The plants should help out the "crop", be easy to grow, self seed well, and be edible. Some could be things like clover, edible but not very palatable. But most should be really good to eat, like purslane. They should probably tolerate dry weather, and some shade from the crops (but shouldn't depend on it.) And I need to be able to get the seed relatively easily, and in large amounts, so that I can just broadcast them into the mulch, and have one in a hundred or so find the right place to sprout. I would probably mix them with compost, sand or biochar. (The biochar would be to heat up the sheet mulch in the spring, just a fine dusting to darken it. Moisture from the snow and biochar induced heating should sprout the 'weeds' pretty well. )

Also, I am wondering about alfalfa. Could this be planted and mowed, and vegetable plants transplanted through it? I would be keeping this mowed down, and piling the cuttings around the plants.

Would the alfalfa rob water from the vegetables? Or would it bring up more water from the subsoil and keep the whole system more hydrated? There is a relatively high water table on the site, and some residual alfalfa plants still growing among the weeds. Of course, the alfalfa could fix and accumulate nutrients.

This is not to be confused with the sheet mulch garden I have been talking about in different posts. I have several projects going on in different locations.

I am currently doing something similar using a mix of sand and ash to go along with my seed mix. Along with purslane i would also include boadleaf plantain and dandelion for young edible greens and good medicinal uses. I have seen lambsquarter up there being weedy in Colorado as well. Other things I have included in my own mix are thistle, wild sunflowers, wild amaranth, goldenrod, wild lettuce, red clover and some other weedy herbs like Thai basil. You will have to look and see what dried seeds you can find in your area.

The three plants that most like to take advantage of newly disturbed soil around here are purslane, amaranth and lamb's quarter. There are commercially available seed for varieties of the first two and quinoa is a close relative of lambs quarters. I like the wild purslane better than the seed I've bought, though I prefer burgundy amaranth to the wild. There are a couple of varieties of orach seed available and I've seen it listed as native to Northern NM, though I haven't noticed it around. It didn't compete particularly well in a couple of trials of 30 or 40 mixed greens I broadcast and then mulched.

I've got feral alfalfa here and there in my garden paths. I see it out amongst the surrounding pinon juniper scrubland also. I've assumed it likes the little extra moisture it gets but I don't worry much about moisture leaving the system because of it. In most places around that aren't dominated by pinon/juniper or sage/chamisa there are clumps of grasses, a few broadleafs, and low shrubs and not much else. Living slands against a background of bare ground. Here, the islands are where the water is. The soil in the islands has some mulch cover as well as shade from the plants. (And roots and life in the soil) Amaranth in particular can form a pretty dense stand and seems to provide enough shade to readily preserve more moisture by blocking evaporation and adding OM to the soil than the plants use. Alfalfa may use more water, but may also add more to the soil.

Not alfalfa unless you WANT chop and drop mulch for a long time. After we plowed under a small annual bed, the old alfalfa came back. I expect it will come back for 10 years or more. All summer I weeded out the volunteer alfalfa to replace it with clover. The older stuff that didn't succumb to the plow, the roots are too hard to dig out. We are accepting them like old cranky neighbors until they die. Yes it has deep roots, but it requires frequent cutting to keep it from taking over. In other places, that's ok because the chooks graze them down, but no chooks are allowed in my little veg plot. We have plenty of alfalfa that we let flower for the bees outside our hard-won annual beds. I wouldn't introduce it in my veg area if I didn't already have it. Under the apples, rock on. Shading my 6 pepper plants, no thanks. There are plenty of clovers/legumes to look into before alfalfa for what you are trying to do.

Thanks for all the suggestions. Would red clover be less weedy that alfalfa? Or should I stick to Dutch white clover?