Most food forest guides spend 90 percent of their attention on the canopy. The real caloric base of the system is underground. A 4 by 8 foot patch of sunchokes alone can produce 50 pounds of tubers per year for a decade without replanting. Add yacon, groundnut, skirret, and a handful of overlooked Andean tubers and a typical backyard food forest will outproduce a same-sized vegetable bed for staple calories every season.
Robert Hart's 1991 forest gardening framework and Martin Crawford's Creating a Forest Garden codified the seven-layer structure now used across temperate permaculture: canopy trees, sub-canopy, shrubs, herbaceous plants, ground covers, vines, and the root layer. The first six get most of the attention in beginner guides. The seventh is where the real caloric work happens.
The root layer makes economic sense for three reasons. First, calories. Roots and tubers concentrate carbohydrates in a way leaves and fruits cannot. A square foot of sunchoke patch easily outproduces a square foot of leafy greens for raw energy. Second, real estate efficiency. Roots occupy soil space that nothing else uses, slotting in below the surface activity of the herb and ground cover layers. Third, soil function. Deep-rooted perennial vegetables work like a permanent broadfork: they break up compaction, mine subsoil minerals, and leave behind air channels and organic matter when harvested.
The USDA NRCS PLANTS Database documents that two of the most productive root crops for North American food forests, sunchokes and groundnut, are native species used as staple foods by Indigenous nations for millennia before European contact. Using them in your food forest is closer to restoration than introduction.
Permaculture's "stack functions" principle: a single design element should do multiple jobs. A row of sunchokes is food, soil builder, late-season pollinator forage, summer windbreak, and ornamental backdrop for shorter plants. That is five functions from one species. Compare with a row of corn (one function: food) or a bag of synthetic fertilizer (one function: nitrogen). The 7th layer of a food forest is the cleanest functional stack in the whole system, which is why the 7-layer model always names the root layer separately.
The other case for the root layer is risk reduction. Above-ground crops fail in years with hail, late frost, hungry deer, or insect outbreaks. Underground crops mostly do not. A sunchoke patch will yield through almost any weather event short of a complete soil freeze in zones 3 to 9. For homesteaders aiming at calorie sovereignty rather than salad sovereignty, the root layer is the most reliable single planting in the system.
Native to North America, hardy zones 3 to 9, reaches 6 to 10 feet tall, produces 2 to 5 pounds of knobby tubers per plant. University of Minnesota Extension documents commercial yields of 25 to 30 tons per acre under good conditions. Tubers store carbohydrate as inulin rather than starch, giving the cooked roots a mild sweetness and a low-glycemic profile. Indigenous Lakota and Dakota nations cultivated and traded the tubers across the Plains long before European contact. Plant once, harvest forever: missed tubers become next year's plants. Place sunchokes at the north edge of your food forest where their height won't shade smaller plants.
Native nitrogen-fixing legume vine, eaten by the Pilgrims through their first winters and praised by Henry David Thoreau in Walden. The vines climb to about 10 feet, useful for training up young fruit trees. Tubers form along underground rhizomes in pearl-like strings, with protein content roughly 3 times that of potato. LSU AgCenter ran a multi-decade breeding program led by William Blackmon and Bill Reynolds that produced larger-tubered cultivars suitable for backyard production. Hardy zones 4 to 8. Tolerates shade better than sunchokes, fits well under the canopy of fruit trees.
Andean perennial daisy relative grown for crisp, juicy, low-glycemic tubers that taste like a cross between an apple and a water chestnut. Single plants produce 5 to 15 pounds of tubers in one season. Frost-tender at the crown but easy to overwinter in cold zones: dig the small reproductive rhizomes from the crown after frost, store in damp peat in a cool basement, replant in spring. Hardy in-ground only in zones 8 to 10, grown as a dig-and-store perennial elsewhere. The tubers store fructooligosaccharides rather than sucrose, of interest to diabetic and prediabetic eaters.
A staple in European kitchen gardens through the 1700s before falling out of fashion. The white finger-like roots taste sweet and parsnippy when steamed. Plant in part shade under the herb layer of your food forest. Hardy zones 4 to 9. Reaches about 3 feet tall with feathery white umbel flowers in summer. Cornell history records skirret as a common American colonial garden vegetable that disappeared as commercial potato cultivation expanded. Easy to divide each spring for more plants.
The most calorically productive crop in the US South. Perennial in zones 9 to 10, grown as an annual elsewhere from slips planted in late May or June. Sprawling vines work as living mulch under the canopy. A single 4 by 4 foot patch can produce 30 to 50 pounds of tubers in a warm summer. Both leaves and roots are edible. NC State Extension maintains the most comprehensive US sweet potato production resources for both commercial and backyard growers.
Mashua (Tropaeolum tuberosum). Andean climbing tuber from the nasturtium family. Spicy, peppery raw, mellows to nutty when cooked. Ornamental orange-red flowers. Hardy as perennial in zones 8 to 10, grown as warm-season annual elsewhere.
Oca (Oxalis tuberosa). Andean tuber, lemony tart. Photoperiod-sensitive: needs short days to tuberize, so harvest comes after the first US fall frost. Multicolored varieties. Hardy at crown to about 25 F if heavily mulched.
Burdock (Arctium lappa). Biennial taproot, eaten as gobo in Japanese cuisine, harvest the deep root in the first year. Excellent subsoil-buster for compacted clay. Tolerates partial shade. Self-seeds aggressively, so cut flower stalks before seed set.
Salsify (Tragopogon porrifolius). Biennial taproot with oyster-like flavor. Purple flowers. Cool-hardy and shade-tolerant.
Chinese yam (Dioscorea polystachya). Long taproots, edible aerial bulbils. WARNING: listed as invasive in several US Southeastern and Mid-Atlantic states. Check your state's invasive plant list before planting. Do not introduce east of the Rockies if you live in a humid temperate region.
The basic rule: match shade tolerance to the canopy density above each root crop. Sunchokes and sweet potatoes are full-sun crops and want to live at the south edge of the food forest or in clearings between trees. American groundnut, skirret, oca, and burdock tolerate dappled shade and are happy under established fruit trees. Mashua tolerates moderate shade and climbs vigorously.
For new food forests, plant roots first or simultaneously with trees. Sunchokes establish faster than apple trees and can act as a nurse crop, providing summer windbreak and dappled shade for tender tree seedlings. Skirret and groundnut can be tucked into the same planting holes as fruit trees, where their soil-building activity actively helps the tree establish.
For mature food forests, the root layer is usually planted in the gaps and edges. Look for spots where canopy gaps allow 4 to 6 hours of direct sun. Those become the sunchoke and sweet potato zones. The deeper shade under mature trees becomes the groundnut and skirret zone. Both layers coexist with whatever ground covers and herbs you have established above them.
| Crop | Lb per plant (typical) | Zones | Sun needs | Best position in food forest |
| Sunchoke | 2 to 5 | 3 to 9 | Full sun | North edge, summer windbreak |
| American groundnut | 1 to 3 | 4 to 8 | Part to full sun | Climbing young fruit trees |
| Yacon | 5 to 15 | 8 to 10 perennial; 4+ as dig-and-store | Full sun | Sunny clearings or south edge |
| Skirret | 0.5 to 1 | 4 to 9 | Part shade | Herb layer under fruit trees |
| Sweet potato | 2 to 5 | Annual most US; perennial 9 to 10 | Full sun | Living mulch around new tree plantings |
| Mashua | 1 to 3 | 8 to 10 perennial; 4+ annual | Part sun | Climbing trellis or shrub edge |
| Oca | 1 to 2 | 7 to 10 perennial; 4+ as dig-and-store | Part sun | Ground cover under fruit trees |
| Burdock | 1 to 2 | 2 to 9 biennial | Part to full sun | Subsoil-busting in degraded patches |
Source: Eric Toensmeier Perennial Vegetables (Chelsea Green, 2007), Martin Crawford Creating a Forest Garden, University of Minnesota Extension, and NC State Extension.
Three rules turn the root layer from a one-shot harvest into a perennial system. First, leave at least 25 percent of the tubers in the ground each fall. Sunchokes and yacon both regrow vigorously from missed tubers. American groundnut returns from the rhizome network and does not need replanting. Second, harvest from one side of each clump at a time. This preserves the established root mass on the other side and means you only need to dig new establishment material every 4 to 5 years. Third, harvest after the first hard frost. Cold temperatures convert starches to sugars in sunchokes, oca, and yacon, transforming the eating experience. Pre-frost tubers are bland; post-frost tubers are sweet.
Designing your first food forest? Start with our complete guide to starting a food forest step by step for planning, layout, and species selection.
Sunchokes were a staple food of multiple Plains nations including the Lakota, Dakota, and Cheyenne. American groundnut was central to the diet of Wampanoag, Lenape, and other Eastern Woodlands peoples and is the tuber Squanto reportedly taught the Plymouth colonists to dig. Three of the most exciting Andean tubers in the global permaculture catalog (yacon, mashua, oca) come from Quechua and Aymara agriculture in the Peruvian and Bolivian Andes, where they were cultivated for thousands of years before any documented European contact.
Using these crops in a US backyard food forest carries a quiet responsibility: credit the source, learn the traditional uses, and treat the planting as part of a living lineage rather than as exotic novelty. The Society of Ethnobiology and Native Seeds/SEARCH are good starting points for deeper context.
The root layer is the most reliable food production in any food forest, but it shines only when paired with the other six layers. Our free guide walks through the canopy, understory, shrub, herb, ground cover, vine, and root layers as a coordinated whole, plus the soil-building and pollinator support that hold them together.
Root crops are the 7th and most overlooked layer of a food forest: edible tubers, taproots, and rhizomes grown for underground harvests. Examples include sunchokes, American groundnut, yacon, skirret, sweet potato, mashua, oca, and burdock. They occupy soil space below the herb and ground cover layers and provide the bulk of caloric production in a mature food forest.
Above ground, Jerusalem artichokes (sunchokes) look like 6 to 10 foot tall sunflower relatives with smaller bright yellow flowers in late summer. Below ground, the edible tubers are knobby and irregular, typically 2 to 5 inches long, with thin brown skin and white-cream flesh. They cluster around the base of the plant.
The name is a mistranslation. The tuber has no connection to Jerusalem and is not a true artichoke. The most accepted etymology is that the Italian word "girasole" (sunflower) was anglicized to "Jerusalem" by 17th-century English speakers, while the cooked flavor reminded early European tasters of artichoke hearts. The plant is native to North America.
Cook them long and hot. The inulin content that causes gas breaks down with extended cooking. Roast at 425 F for at least 45 minutes, simmer in soup for 30 to 40 minutes, or ferment them as pickles. Start with small portions (1/2 cup cooked) and increase over 2 to 3 weeks as your gut microbiome adapts. Pairing with hard cheese or yogurt also helps.
Yes. They are high in inulin, a prebiotic fiber that supports beneficial gut bacteria. They have a low glycemic index, making them suitable for diabetic and prediabetic diets. They are rich in iron, potassium, and B vitamins. The main caveat is that the prebiotic effect can cause digestive gas, particularly when first introducing them.
Plant yacon crown divisions in spring after the last frost. Space 3 feet apart, give full sun, and water steadily through summer. The plant reaches 6 to 8 feet by fall. Harvest after the first frost kills the tops. Dig the large eating tubers and separate them from the smaller reproductive rhizomes at the crown. Store the reproductive rhizomes in damp peat at 40 to 50 F over winter, replant in spring.
American groundnut (Apios americana) is a native North American nitrogen-fixing legume vine that produces small protein-rich tubers along underground rhizomes. It was an important Indigenous food crop in the Eastern Woodlands and sustained the Plymouth colonists through their first winters. The vine climbs to about 10 feet and produces clusters of fragrant maroon-purple flowers in summer.
Plant skirret crown divisions in spring in moist, fertile soil with part shade. Space 12 to 18 inches apart. The plant reaches 3 feet tall and produces white umbel flowers in summer. Harvest the white finger-like roots in late fall after the first frost. Reserve a few crown divisions each spring to replant. Skirret is happiest in the understory of a food forest where it gets dappled light.