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American Groundnut
A native twining legume vine that grows strings of protein-rich edible tubers underground - the wild 'potato bean' that fed Indigenous peoples and helped the Pilgrims survive, crowned with fragrant maroon flowers.
Safety notes Groundnut tubers are a nutritious native food, but ALWAYS COOK THEM - never raw; try a small amount first, as a minority react mildly. Identify it before eating: a slender NON-WOODY twining vine, pinnate leaves of 5-7 leaflets, fragrant MAROON pea flowers, and beaded chains of tubers underground. Wisteria shares these damp thickets and hangs bean-like pods but is WOODY with lilac-blue flowers, and its pods and seeds are toxic - never collect pods from a woody vine. Forage herbicide-free ground.
Overview
American groundnut (Apios americana), also called hopniss or the potato bean, is one of North America's most remarkable native food plants: a twining legume vine that climbs over shrubs and thickets to 3-10 feet, blooms with dense clusters of fragrant maroon flowers, and - the real prize - grows a string of protein-rich edible tubers underground, threaded like beads along its roots. Cooked, the tubers are nutty, dense, and potato-like, but with far more protein than a true potato (as you'd expect from a legume), making them an unusually nourishing wild root. It is not the peanut, which is called groundnut through much of Britain, Africa, and Asia - that is Arachis hypogaea, an unrelated annual with its own guide here. Nor is it the cinnamon vine or Chinese yam (Dioscorea polystachya), an unrelated invasive twiner of the same damp thickets that carries little aerial bulbils groundnut never has.
Quick facts
- Sprouts in
- 30 daysRange: 14–60 days
- Soil temperature
- 70 °FRange: 60–80 °F
- Height
- 7 ftRange: 3–10 ft
- Spread
- 24 inRange: 12–48 in
- Support
- Grows better on a trellis or stake
- Cold
- Takes hard frostdamaged below -30°F
- Heat
- Struggles above 95°F
- Life cycle
- Perennial, lives about 10 years
- Save seeds
- About 150 days after plantingRange: 120–180 days
- Self-sows
- Yes, expect volunteers
- Soil
- Consistently moist
- Water
- Medium
- Plant spacing
- 18 inRange: 12–30 in
When to plant
Nothing is open today. Spring planting opens 5 months, Mar 27 to May 22.
- Plant tubers Mar 27 – May 22 Opens in 158 daysAbout 2 weeks before to 6 weeks after your last frost (Apr 10 here)Plant tubers in spring in moist, rich soil with support to climb; groundnut establishes and forms tuber chains over a season or two. A slow but permanent, self-renewing perennial patch.
- Direct sow Apr 10 – May 8 Opens in 172 daysAbout at to 4 weeks after your last frost (Apr 10 here)Where seed is available (mostly from southern, pod-setting plants), sow scarified seed in warm, moist soil; growth from seed is slower than from tubers. Far more often it is grown from tubers or foraged where it grows wild.
Frost here: last around Apr 10 (Mar 27 to Apr 24 most years), first around Oct 25. Zone averages, your own yard may run a week or two either way.
Life stages
Establish, grow, repeat
Getting established and returning each season are different parts of the story.
Stage 1 of 4 · Getting established
Tubers sprouting / vining up
Day 0 to 70 from sowing
Care at this stage
-
Give the twining vine something to climb
Groundnut is a twining legume VINE - it climbs by wrapping around stems, shrubs, fences, or a trellis, reaching 3-10 feet. Provide support at planting; in the wild it scrambles over shrubs and thickets. As a legume it also fixes nitrogen, enriching the soil.
-
Keep moist - it loves damp ground
Groundnut thrives in moist to wet, rich soil along stream banks, thickets, and damp woods. Keep new tubers watered to establish; steady moisture builds the string of edible tubers along its underground runners.
Months are typical seasonal windows; climate, variety, and plant age can shift them.
Harvest
- Tuber chains along the runners, largest and best after a season or two - dig fall through early spring
- Cook before eating; where pods set, ripe bean-like seeds are edible cooked
- Dig the tuber chains in fall (and cook them) · every 2 weeks
- A perennial patch you harvest and replant
Picking pick as they ripen
Cook with American Groundnut
Watch out for
3 to know. None are high-risk for American Groundnut. 2 are active in October.
Cook-Before-Eating & Mild AllergySeverity Medium DisordernowSeason: Mar, Apr, Sep, Oct, NovN/A as a plant condition - the caution is dietary: raw tubers, and rare mild allergic reactions in sensitive people (sometimes on repeated eating).
N/A as a plant condition - the caution is dietary: raw tubers, and rare mild allergic reactions in sensitive people (sometimes on repeated eating).
Cook thoroughly; if a mild reaction occurs, discontinue eating it. Otherwise no action needed - cooked groundnut is a wholesome, nourishing food for most people.
Always cook the tubers (boil, roast, or fry) - never eat them raw; try a small amount the first time and watch for any reaction before eating more.
A food-safety note rather than a plant problem: groundnut tubers are a legume and must be COOKED (never eaten raw), and a minority of people report a mild allergic reaction, sometimes only after eating it repeatedly.
Voles & RodentsSeverity Low WildlifenowSeason: Sep–FebA hosta that fails to sprout in spring, a crown that lifts easily because roots are gone, surface runways and holes under the mulch.
A hosta that fails to sprout in spring, a crown that lifts easily because roots are gone, surface runways and holes under the mulch.
Dig tubers before heavy winter rodent activity; the vigorous, tuber-chaining plant usually shrugs off modest losses and regrows from remaining tubers.
Harvest the larger tubers in fall rather than leaving a full crop over winter; a contained bed or hardware-cloth barrier protects tubers where rodent pressure is high.
The nutritious underground tubers are food for voles, mice, and other rodents (as well as some larger wildlife), which dig and gnaw them, especially over winter - a mark of the plant's food value as much as a nuisance.
Aggressive Tuber SpreadSeverity Low DisorderSeason: Jun–SepVines twining over and smothering neighboring plants, and new shoots emerging from tubers well beyond where it was planted.
Vines twining over and smothering neighboring plants, and new shoots emerging from tubers well beyond where it was planted.
Dig out wandering tubers (get the runners) and cut back smothering vines; a contained bed or a spot it can freely fill keeps it productive without taking over.
Site it where its spread is welcome (a damp thicket, a dedicated bed, or a large container), give it strong support, and keep it from climbing over prized plants.
Not a pest but groundnut's spreading habit: it multiplies by chains of tubers and runners (and any tuber left behind regrows), so it forms an expanding, near-permanent patch that can wander into beds or climb over desirable plants.
Good & bad neighbors
All of these are traditional pairings. The evidence is thin, so treat them as a nudge, not a rule.
Plant nearby
-
A traditional native pairing in spirit: as a twining nitrogen-fixing legume vine, groundnut climbs tall stalks like corn (echoing the bean of the Three Sisters) and enriches the soil with nitrogen - though it is vigorous, so give it room and strong support and keep it from smothering the crop.
-
A common companion of the damp thickets and edges where groundnut grows; its early flowers feed pollinators and its taproot mines minerals, a soft, traditional benefit in a diverse native food patch.
-
A fellow twining, nitrogen-fixing legume with the same climbing habit and soil-enriching benefit; growing pole beans is a good way to understand groundnut's vine and legume nature (and both want support to climb).
-
A low native groundcover that suits the same moist, part-shaded edges where groundnut vines up shrubs; the strawberry carpets the ground while groundnut climbs above, a layered native edible planting.
Varieties · 3
You pick one when you add American Groundnut to your garden. Its days to maturity set your harvest window.
American Groundnut (Apios americana)
The wild American groundnut (hopniss): a hardy native twining legume vine of moist woods and stream banks, with fragrant maroon flowers and strings of protein-rich edible tubers along its roots.
Variety details for American Groundnut (Apios americana)
Twining vine with pinnate compound leaves, dense clusters of maroon pea-like flowers, and beaded chains of tubers underground.
speciesnativeedible-tubersvineCooked as a nutty, nourishing potato-like food; the staple wild root that fed Indigenous peoples and early settlers.
Improved / Selected Groundnut (LSU and other selections)
Groundnut lines selected and bred (notably in Louisiana State University research) for larger, faster-bulking tubers and better yields as a potential sustainable food crop - the same nutritious native, chosen for more productive, kitchen-friendly tubers.
Variety details for Improved / Selected Groundnut (LSU and other selections)
Vigorous twining vine as the wild type, with larger, heavier tuber chains.
selectedlarger-tubersfastercropGrown from tubers like the wild plant.
Price's Groundnut (Apios priceana)
A rare related native groundnut of the Southeast that forms one large tuber rather than a chain, with pinkish flowers.
Variety details for Price's Groundnut (Apios priceana)
Twining vine with pinkish-maroon flowers and a single large tuber; rare in the wild.
speciesnativeraresingle-tuberIt is federally listed as THREATENED under the Endangered Species Act and protected by several states (AL, KY, MS, TN): collecting, digging, transporting, or trading wild plants is illegal. Listed here only so you can recognize it and leave it alone - not as a plant to grow or harvest.
Grower tips
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