How to Grow Ullucos USA

By the SoilCommander Editorial Team, under the guidance of Nitin Sharma, Co-Founder · · How we check our facts

On this page
  1. Ulluco (Ullucus tuberosus)
  2. Quick Facts
  3. At a Glance
  4. Diseases
  5. Pests
  6. Growth Stages
  7. Harvest & Storage
  8. Plan your Ullucos planting
  9. Growing Ulluco in another region
  10. Sources
  11. Frequently Asked Questions

Ulluco is a short-day Andean tuber — tuber bulking doesn't start in earnest until day length drops to around 13 hours or less (12 hours or less in most varieties), which in the Northern Hemisphere falls after the autumn equinox, so a long, mild, frost-free fall is what actually sizes the crop. It also performs poorly in heat, stalling above 80°F (27°C), which is why Cultivariable considers the cool coastal strip up to San Francisco, CA (USDA zone 9a) about as far south as it reliably thrives in the US.

Core growing advice on this page is checked against named horticultural sources — see References.

Ulluco (Ullucus tuberosus)

A young ulluco (Ullucus tuberosus) plant growing in a raised bed — “Kluse - Ullucus tuberosus 01 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.

2 sources cited · Verified

Quick Facts

A young ulluco (Ullucus tuberosus) plant growing in a raised bed — “Kluse - Ullucus tuberosus 01 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 01 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
Factor Value
Drainage Thrives even in poor soil (Cultivariable); loose, light soil is an advantage at harvest time; moderately acidic preferred; compost outperforms synthetic fertiliser.
Lifecycle Tender tuberous perennial grown as an annual. Cultivariable: best suited to USDA zone 9a and cool maritime climates; performs poorly above 80°F (27°C), with even brief hot spells cutting yield.
Edible parts tubers, leaves
Documented problems 5 diseases, 4 pests

At a Glance

A colourful selection of ulluco tubers in red, orange and yellow — “Kluse - Ullucus tuberosus 08 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 08 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
Ullucus tuberosus Ulluco Potato leafroll virus d… Papaya mosaic virus dis… Verticillium wilt Ulluco mosaic virus dis… Black scurf and stem ca… Voles Cucumber beetles Slugs Mice DISEASES PESTS

Diseases

Close-up of ulluco's succulent, angular stems and leaves — “Kluse - Ullucus tuberosus 05 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 05 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
Potato leafroll virus disease

Potato leafroll virus

Cultivariable: Potato leafroll virus is one of the most common viruses found in heirloom ulluco stock.

Papaya mosaic virus disease

Papaya mosaic virus

Cultivariable: Papaya mosaic virus is one of the most common viruses found in heirloom ulluco stock -- over 90% of heirloom varieties carry some virus; seed-grown stock tests clean.

Verticillium wilt

Verticillium dahliae

Cultivariable: Verticillium wilt is the most serious fungal threat to ulluco, with symptoms worsening above 75°F/75°F (24°C).

Ulluco mosaic virus disease

Ulluco mosaic virus

Cultivariable: an Ulluco mosaic virus is one of the most common viruses found in heirloom ulluco stock.

Black scurf and stem canker

Rhizoctonia solani

Cultivariable: Rhizoctonia solani reduces ulluco yields and increases storage losses -- the same soil-borne pathogen behind potato black scurf.

Pests

Freshly harvested yellow ulluco tubers from Peru — “Kluse - Ullucus tuberosus 06 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 06 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
Voles

Microtus spp. / Arvicola spp.

Cultivariable: voles damage ulluco by severing stems at ground level, alongside mice.

Cucumber beetles

Diabroticina (various spp.)

Cultivariable: cucumber beetles are reported as serious pests of ulluco in some regions.

Slugs

Gastropoda (slugs, various spp.)

Cultivariable: slugs threaten young ulluco plants.

Mice

Muridae (mice, various spp.)

Cultivariable: field mice damage ulluco by severing stems at ground level.

Growth Stages

An ulluco plant with small flower buds among its succulent leaves — “Kluse - Ullucus tuberosus 04 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 04 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
Stage BBCH Notes
Planting 0 Cultivariable: plant whole or cut seed tubers (with at least two eyes) once frost danger has passed, at a depth equal to the tuber's diameter; space plants about 15in apart in rows 24-36in apart. Plant roughly seven months before the expected first autumn frost to allow enough time to mature.
Canopy establishment 3 Cultivariable: plants form a dense, sprawling ground cover to about 3ft (91cm) across and 15in (38cm) tall, effectively suppressing weeds once established. Full sun gives the best tuber production, though afternoon shade helps where summers run hot -- growth stalls badly above 80°F (27°C).
Tuber initiation (short-day trigger) 5 Cultivariable: the main tuber-forming trigger only switches on once day length drops to around 13 hours or less, typically after the autumn equinox -- an honestly late and weather-dependent stage in a UK growing year, the same short-day tension already documented for Oca.
Tuber bulking and harvest 8 Cultivariable: tubers keep bulking through November into December/January; earliest worthwhile harvest is mid-November, with full maturity not reached until late December or January. Tubers tolerate a freeze better than the foliage does (about 75% viability after 25°F/25°F (-4°C)), so a mild, frost-free autumn is what actually decides the size of the crop.

Harvest & Storage

A harvested pile of ulluco tubers from southern Peru — “Kluse - Ullucus tuberosus 09 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.
“Kluse - Ullucus tuberosus 09 ies” by Frank Vincentz is licensed under CC BY-SA 3.0.

When to pick: Cultivariable: earliest worthwhile harvest is mid-November (around 50% of potential yield); mid-December approaches 80%; full maturity is reached in late December or January, when most varieties have formed over 100 tubers per plant, though often only around a third are of a marketable size.

Storage

Cultivariable: store at 34-38°F (1-3°C), 90% humidity, in the dark -- ulluco has been known to keep for up to two years under these conditions, with one year readily achievable.

Plan your Ullucos planting

When to sow and plant Ullucos depends on your own frost dates. Check the USA vegetable planting calendar. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.

Growing Ulluco in another region

Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.

Sources

The full list of 2 sources behind this guide (Cultivariable, International Potato Center (CIP)) is in the references of our UK guide to ulluco; they describe the plant itself, which is the same wherever it grows.

Frequently Asked Questions

What problems affect ulluco?

Our data links 5 diseases and 4 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.

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SoilCommander Editorial Team — under the guidance of Nitin Sharma, Co-Founder

Every growing guide is checked against RHS, USDA Cooperative Extension, and other named horticultural authorities before publishing. How we check our facts.

How this guide is put together

The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against USDA hardiness-zone and frost-date data, with Cooperative Extension sources cited directly where one exists for a crop. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.

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Last verified 2026-09-05

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