Up in Boulder, my parents have a grape vine that produces bountifully every year with almost no inputs whatsoever (only some watering in the summer).
Thompson grapes, I think. Dark purple when ripe, very sweet, great for jam, crap for wine.
It grows along an old picket
fence that encloses their front
yard. They don't prune, fertilize, mulch, or anything.
I also met a guy who had developed a system (I think near Colo Springs) for using
mushrooms to help plants grow inside a
greenhouse. He said he was getting 7 crops of marijuana a year, and "was beginning to experiment with the technique in the vegetable garden". Basically, it goes something like this: build raised beds. inoculate some big pieces of
wood with primary-decomposer fungi (eg oyster mushrooms), and use these as the bottom layer on the raised beds. Add some smaller pieces of wood too, also inoculated with primary-decomposers. Fill in with dirt and cover the whole bed with a thick (4-6"?) layer of leaves (also perhaps inoculated). Wet the whole thing thoroughly. After a couple of weeks, he said, it's practically like cement, the leaves are so stuck together with mycelium (you might have to
water some to keep it from drying out). Then dig a hole (he used a piece of rebar to get through the leaves and make his planting hole). Insert a seedling that has been inoculated with mycorrhizal fungi. As the primary decomposers work through the wood/leaves, they leave material in a state that the mycorrhizal fungi, being secondary decomposers, can take up and make available to the plant
roots. When his plants have reached near-maturity, he plants another batch in between them, which take advantage of the shade to get settled in and develop roots. Then 1-2 weeks later he cuts the mature plants, giving the young ones full sun. Rinse and repeat.
The benefits of this system are:
Water retentionHeat production (fungi produce heat as they break things down)
Weed controlExtra nutrients for the plantsEdible mushroom harvest (from time to time, if you're lucky)
Extra oxygen for the plants (fungi breathe like we do, and plants can absorb more CO2 then they normally have access to. mostly this can only be captured in a greenhouse)
In fact, pretty much all those things carry over outside the greenhouse too, except that the extra CO2 produced usually escapes the system.