Can you tell I live in the Deep South from that title? There is a reason certain foods are featured in certain cuisines -- they grow well there! In fact, I've had volunteers from last year's crop for all three of these pop up on their own. But since I went and dug down 8" and built up 18" to make my hugelbeds, I'm starting from new seed this time. Now we will see what they can really do.
Peanuts and sweet potatoes are low spreading crops, and okra is the tall crop (I've had some go as tall as 8' before the frost got them), so that leaves a middle-size, bushy type crop to fill out the triad. This year, I'm filling that niche with eggplant and hot peppers.
Agricultural research has a big blind spot when it comes to intercropping, with most of the serious studies taking place in Third World countries. American universities are still in the thrall of agribusiness, with its unquestioned acceptance of (large) monocultures. But the days of big agribusiness may be coming to a close. High fossil fuel inputs to agriculture in the way of diesel fuel for tractors and fertilizer manufacture aren't sustainable. Pesticide and herbicide use to create an otherwise sterile culture medium for one crop plant isn't sustainable. What is sustainable is growing a polyculture, with decaying organic matter as fertilizer, and clever and labor-intensive methods used to foil weeds and pests.
My 25' row of potatoes is still growing, compared to last year, when potato harvest was around the first of May. Even though spring was late in coming this year, the summer heat is holding off and giving the potato plants time to grow and set 'taters. And this year I am having little to no bug problem. Maybe a few small holes on just a few plants. I don't know whether to attribute it to the regular compost tea applications, or the companion planting of red clover and cilantro that surround the potato row, but something is working right. It bothers me as a scientist that I can't isolate and rank all the success factors, but in consolation, maybe I am learning how to be a successful gardener in a multi-, multi-variate world.