How to Grow Hopniss UK | Planting & Establishment

Hopniss (Apios americana)

A string of hopniss tubers strung along an underground runner. Photo: Eric Toensmeier, CC BY-SA 3.0, via Wikimedia Commons.

Also known as: Potato Bean, Groundnut · 2 sources cited

Hopniss (Apios americana) — Hardy herbaceous perennial climber, dying back each winter and regrowing from its tubers.

Unlike an annual crop, the work here is front-loaded into establishment: get the planting and the site right and the same plants crop for several seasons.

Soil & Growing Conditions

Hopniss growing at the water's edge — “Apios americana - 50286730862” by sonnia hill is licensed under CC BY 2.0. Source: Wikimedia Commons — “Apios americana - 50286730862” by sonnia hill is licensed under CC BY 2.0. Source: Wikimedia Commons.

Water: High; a plant of marshes, wet thickets and stream banks

Soil pH range

5 7.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Quick Facts

A single hopniss tuber with its runner still attached — “Apios americana - American groundnut (Indian potato) tuber” by James St. John is licensed under CC BY 2.0. Source: Wikimedia Commons — “Apios americana - American groundnut (Indian potato) tuber” by James St. John is licensed under CC BY 2.0. Source: Wikimedia Commons.

Factor	Value
Soil pH	5 - 7.5
Soil texture	High organic matter, loam, sand or shallow rocky ground
Drainage	Moist to occasionally wet
Lifecycle	Hardy herbaceous perennial climber, dying back each winter and regrowing from its tubers.

Harvest & Storage

A handful of freshly lifted hopniss tubers — “Large groundnut tubers” by Eric Toensmeier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons — “Large groundnut tubers” by Eric Toensmeier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons.

When to pick: Tubers can be lifted in the first year but take 2-3 years to make a worthwhile crop. They form in strings along the runners, so lift carefully and replant the small ones.

Hopniss through the season

A string of hopniss tubers strung along an underground runner — “Groundnut tubers” by Eric Toensmeier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons — “Groundnut tubers” by Eric Toensmeier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons.

How the crop forms

Tubers are strung along the underground runners like beads. This is what makes hopniss productive, and also what makes it persistent.

A single tuber

Lifted with the runner still attached. Replant the small ones as you go and the bed keeps itself going.

A harvest

Tubers can be lifted in the first year but take two to three years to make a worthwhile crop.

Hopniss tubers cut open to show the pale interior — “Apios americana tubers” by Malte is licensed under CC BY-SA 3.0. Source: Wikimedia Commons — “Apios americana tubers” by Malte is licensed under CC BY-SA 3.0. Source: Wikimedia Commons.

Inside

NC State compares the cooked tuber to a potato but nuttier and finer in texture, with appreciably more protein.

The maroon and pink flowers of hopniss — “Apios americana in flower (American groundnut; Indian potato) 1 (20278465435)” by James St. John is licensed under CC BY 2.0. Source: Wikimedia Commons — “Apios americana in flower (American groundnut; Indian potato) 1 (20278465435)” by James St. John is licensed under CC BY 2.0. Source: Wikimedia Commons.

The flower

Maroon and pink, and strongly scented. Hopniss is a legume, and fixes its own nitrogen.

Buds

Flowering comes in mid to late summer on established plants.

Hopniss twining up a tree trunk — “Apios americana 15-p.bot-apio.ame-0023” by Ayotte, Gilles, 1948- is licensed under CC BY-SA 4.0. Source: Wikimedia Commons — “Apios americana 15-p.bot-apio.ame-0023” by Ayotte, Gilles, 1948- is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

It climbs

A vine 8-16 feet long that will use whatever support it finds, including standing trees.

A dense colony of hopniss covering low ground — “Apios americana 15-p.bot-apio.ame-0013” by Ayotte, Gilles, 1948- is licensed under CC BY-SA 4.0. Source: Wikimedia Commons — “Apios americana 15-p.bot-apio.ame-0013” by Ayotte, Gilles, 1948- is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

And it spreads

NC State records that it can become weedy and will spread to form colonies. Give it a contained bed rather than a mixed border.

Where it grows wild

A plant of tidal and non-tidal marshes, wet thickets and stream banks. A damp corner suits it.

Hopniss trained up a support in a botanical garden bed — “Apios americana - Urban Greening Botanical Garden - Kiba Park - Koto, Tokyo, Japan - DSC05388” by Daderot is licensed under CC0. Source: Wikimedia Commons — “Apios americana - Urban Greening Botanical Garden - Kiba Park - Koto, Tokyo, Japan - DSC05388” by Daderot is licensed under CC0. Source: Wikimedia Commons.

In cultivation

Grown up a support in a botanical garden bed. Hardy to USDA zone 4, so most of Britain and Canada can grow it outdoors.

References

2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.

Frequently Asked Questions

What soil pH do hopniss need?

A pH of about 5–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

Plan next season before the problems start

Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.

Get the UK Garden Planner →

Instant PDF download · Written for UK growing conditions

SoilCommander Editorial Team

UK vegetable growing guides · Checked against RHS & Met Office guidance

Every SoilCommander guide is written and maintained by our editorial team for real UK growing conditions, and reviewed against Royal Horticultural Society growing advice and Met Office climate data before publication.

Vegetable Growing Guides UK

Relevant next steps

Where To Go From Here

Take this crop from reading into a written plan for your own beds.

UK garden plannerTurn this crop guide into sowing dates, bed layouts and a harvest record. All growing guidesBrowse every crop we cover for your region, A to Z. Planting CalendarSee how this crop fits alongside everything else you are growing.

Plan the next step

Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.

Get Planner

How to Grow Hopniss UK | Planting & Establishment

Hopniss (Apios americana)

Soil & Growing Conditions

Quick Facts

Harvest & Storage

Hopniss through the season

References

Frequently Asked Questions

Where To Go From Here

Plan the next step

Join our email list

Your cart is empty

Your cart is empty

How to Grow Hopniss UK | Planting & Establishment

Hopniss (Apios americana)

Soil & Growing Conditions

Quick Facts

Harvest & Storage

Hopniss through the season

References

Frequently Asked Questions

Where To Go From Here

Plan your veg garden before you dig a single inch

Plan the next step