I am planning a food forest, climate is mediterranean, and I plan using almost only edible species which are starchy or protein staples (yes I know I am deeply focused in that issue, eheh). If they could be eaten raw, then it's even further great, but that seems to much challenging to find!
I plan having 3 habitats: in spots with walnuts and chestnuts (more shade to understory) and other spots (more light to understory and perhaps even wide sunny spots, kind of a grassland with a few trees) with bamboos, olive trees. honeylocust, carob, dates, siberian pea shrubs, elaeagnus. Third habitat is a pond, open space with water loving species. I might plant annual staples in these 3 habitats too.
So far the property, already has the 3 habitats: an untouched chestnut forest, grassland with olive trees only, and a pond.
Now I have to fill with the ground covers, herbaceous and the climbers, and all the trees I mentioned.
I want to group in guilds, where there is at least one or two n-fixers. But I want most species to be good filling food, stuff like starchy roots, pulses and nuts!
Ground covers: as I see it, the most useful species, feeding staples would be potatoes, sweet potatoes and peanuts (but they are more kind of annuals). It's easy to find species for sunny ground covers, but for forest shade understory, I can think of ramps, some other alliums perhaps, tiger nuts... but I can't think of something that provides really a good food crop, for that spot.
Now as large trees chestnuts and walnuts are very important, because they provide nice starch, oil and protein food. Hazelnuts can go to the understory, as their nuts are also a rich food.
At the grassland I can plant my cereals, corn, pulses, potatoes, pumpkins, the stuff that is really staples.
At the pond, I can plant rice, arrowhead, cattails, and perhaps tiger nuts as well. I know there are a few more species but I haven't experimented with them yet.
The largest problem is finding trees or shrubs for the climbers to climb. Where can I put a dioscorea yam?
What about the groundnut (apios)? Can it stand some shadow?
Perhaps it can be use at the foot of some small shrub; perhaps the hazelnuts, bamboos, avocados or olive trees.
The other species I thought for filling the space would be jujube, enset, pigeon peas, earthnuts, lima beans... again interested mostly in first setting a staple food forest (things that I can base my diet in)
in Portugal, sheltered terraces facing eastwards, high water table, uphill original forest of pines, oaks and chestnuts. 2000m2
in Iceland: converted flat lawn, compacted poor soil, cold, windy, humid climate, cold, short summer. 50m2
Groundnuts can tolerate moderate shade, I haven't grown them myself but have seen them in part shade under trees. They can sprawl pretty aggressively, personally I wouldn't put them on a tree/shrub that I wanted production from. Also harvesting the roots could potentially damage your tree roots. Some folks like to grow them on sunchokes, so then you're digging up two crops at once.
Wild yam grows here on forest edges. It grows sporadically in the understory, but the really large sprawling vines are on the sunnier edges.
I would suggest also thinking about fruits. They aren't necessarily staples, but when they're fresh they can make up a significant portion of your diet.
I recommend growing Chayote. The fruits and roots are both great the leaves are said to be edible but not by my standards. The roots are a great tasting way to get carbs but digging them is very laborious. You have to make a 3feet deep hole 1 foot (or more depending on the size of the primary root system) from the plant then start undermining to get at the stogage roots underneath leaving the plant intact. Its a vine so its a really good plant for that deep dark spot, well not too dark but mine grow in trees that are 15-30 feet tall. Ideal tree hight is about 20 feet. Plant chayote 50% submerged in soil covering, completely submerging the seed will cause it to rot. Plant at least 4 feet from the base of larger trees or 2 feet from small peach trees and such. Its herbaceous and may need straw in winter if it gets temps less than -2. You can also use frost huts in spring which are 3-4 feet high made from stakes with a debris roof they work to an extent but a hard frost will still set the plant back eliminating the fruit harvest for that year and possibly reducing root harvest.
There is data for the tubers available in scientific reports from Veracruz if you want to look them up.
Diversified Food forest maker . Fill every niche and you'll have less weeds (the weeds are the crop too). Fruit, greens, wild harvest, and nuts as staple. Food processing and preservation are key to self self-sufficiency. Never eat a plant without posetive identification and/or consulting an expert.
Some great resouces to be found on the Plants for a future website PFAF.org Plants for a Future you can make your seach very specific and find tons of useful plants for the exact niches you are seeking to fill. another tip for building guilds would be to take the tree (in your case, olive or walnuts) you are basing the guild around, and seach for "Olea europaea, plant communities" or "Juglans nigra (if it's a black walnut) plant associations". this is a good way to find scholarly, reliable information about what plants will pair well with the tree you are basing your guild around.
as for specific starches, you mentionned potatoes, Chinese yams (Dioscorea batatas) are a perennial root that tastes great, will probably thrive in your climate with adequate watering, and gets HUGE! the roots of old plants (5 yrs+) get rediculous. like 2 people to lift rediculous....
anyways I have always found it more helpful when people suggest resources than specific plants so check out the plants for a future website pfaf.org, look up plant associations on google or on some scholarly database, and if you haven't already, read Toby Hemenway's book 'Gaia's Garden'. I can't give enough props to Toby Hemenway. amazing useful book that is very accessible (unlike mollison's permaculture designer's manual) and super helpful as a handbook when designing permaculture systems of any size.
hope this helps,