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How to Grow Mashuas | Care, Pests & Disease Control
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Bacterial tuber staining (mashua, causal agent not yet confirmed)
low
Named only vaguely by Cultivariable (brown bacterial staining in wet, warm soil), no species identified -- generic entry created rather than guessing a pathogen.
Cucumber mosaic virus
low
Cucumber mosaic virus (CMV)
Named specifically by Cultivariable, alongside potyviruses and Papaya mosaic virus; RHS separately gives a general virus-susceptibility warning for the UK garden cultivar. Mostly mild or asymptomatic in North American…
Powdery scab
low
Spongospora subterranea
Raised or sunken scabby patches on tuber/root skin
Named specifically by Cultivariable as powdery scab (Spongospora subterranea).
Mashua virus diseases (potyviruses and Papaya mosaic virus, unspecified)
low
Covers Cultivariable's potyviruses (possibly Bean Yellow Mosaic, Turnip Mosaic, or unidentified mashua-specific strains) and Papaya mosaic virus, grouped since neither is singularly confirmed.
Moist but well-drained (RHS); Cultivariable: tolerates poor soil, loose/light soil best for harvest, moderately acidic.
Lifecycle
Tuberous, climbing perennial. RHS rates the 'Ken Aslet' garden form H3 (-5 to 1C), hardy only in coastal and relatively mild parts of the UK. Cultivariable gives USDA zone 9a as the best fit, noting about half the tubers survive a multi-day freeze at 25F.
Cultivariable: plant whole or cut tubers (each piece at least 1/2oz with two or more eyes) 2-3in deep after frost danger passes, 30in row spacing; give the climbing stems support to grow up. RHS: propagate 'Ken Aslet' by division of the tuberous rootstock.
Climbing growth
3
RHS: grow in full sun or partial shade, sheltered, moist but well-drained soil; wear gloves when handling, as the plant is a skin allergen. Cultivariable: performs best where summer highs stay below 80F, with afternoon shade helpful in hotter spells.
Day-length triggered tuber formation
4
Cultivariable: most mashua varieties are short-day plants, needing a critical day length of around 13 hours before tubers begin forming in early September -- the RHS-favoured 'Ken Aslet' cultivar has a longer critical day length, tuberising earlier in mid-summer, which likely explains its popularity as the standard UK garden form.
Harvest and overwintering
8
Cultivariable: tubers need about 10 weeks after formation to size up, harvested around mid-November. RHS: lift and store tubers somewhere frost-free over winter, or grow the plant in a deep container that can be moved indoors.
When to pick: Cultivariable: tubers need about 10 weeks after formation to reach good size, harvest falling around mid-November; colour develops late, so fully coloured varieties benefit from maturing as long as possible before frost.
Storage
Tubers keep 6-8 weeks at room temperature, or up to 8 months at 35-38F/95% humidity; can also be frozen chuno-style for longer preservation (Cultivariable).
'Yawar Waqay' (Quechua for 'crying blood') is one of many named mashua cultivars maintained by Andean growers, reflecting the crop's long cultivation history.
Light: full sun in mild climates, afternoon shade where temperatures often exceed 80F; needs cool summers (ideally not above 80F). Soil: tolerates poor soil, loose/light soil best for harvest, moderately acidic, minimal fertiliser needed. Size: 8-12ft climbing height given support, tubers 3-8in (to 13in). Hardiness: USDA zone 9a (20-25F), ~50% of tubers survive a multi-day freeze at 25F; does well in the maritime Pacific Northwest. Day length: most varieties need ~13h critical day length, tuber formation starting early September; 'Ken Aslet' has a longer critical day length, tuberising mid-summer. Planting: whole or cut tubers (min 1/2oz per piece, 2+ eyes) 2-3in deep after frost, 30in row spacing; seed started 3+ months ahead at 55-65F. Propagation: vegetative (tubers/cuttings) or seed (not true to type), hummingbird/bumblebee pollinated. Pests: deer (most serious), cabbage white butterfly larvae, flea beetles, aphids, field mice; bears/waterfowl can destroy plantings. Diseases: potyviruses (possibly Bean Yellow Mosaic, Turnip Mosaic, or mashua-specific strains), Cucumber Mosaic Virus, Papaya Mosaic Virus (mostly mild/asymptomatic in North American stock); powdery scab (Spongospora subterranea); bacterial brown staining in wet, warm soil. Harvest: tubers need ~10 weeks after formation, around mid-November; colour develops late, so full-colour varieties benefit from maturing as long as possible before frost. Storage: 6-8 weeks at room temperature, up to 8 months at 35-38F/95% humidity; can be frozen (chuno-style) for longer preservation. Edible use: all parts edible -- tubers cabbagey when cooked (raw tubers unpleasant, glucosinolates), leaves a spicy mustard-like salad green, flowers sweet with aniseed notes; high in vitamin C, contains isothiocyanates.
Hardiness H3 (-5 to 1C, coastal and relatively mild parts of the UK). Soil: clay, loam, sand, moist but well-drained, acid or neutral pH. Sun/aspect: full sun or partial shade, any aspect. Exposure: sheltered. Size: 2.5-4m height, 0.5-1m spread, 2-5 years to maturity. Propagation: division of the tuberous rootstock. Pests: glasshouse whitefly, red spider mite. Diseases: susceptible to virus diseases affecting vigour. Safety: skin allergen, wear gloves when handling. Notable: AGM-winning cultivar, orange flowers with brown veining and red spurs; earlier-flowering with bluish foliage, grows well in Britain on a sunny wall. Overwintering: lift and store tubers frost-free, or grow in a deep container overwintered indoors.
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 problems affect mashuas?
Our data links 4 diseases and 7 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
This page gives you the thresholds; the planner turns them into your own calendar. It works from what you can observe and measure in your garden rather than from dates written for somebody else’s latitude.
Science-based growing guides · Thresholds that hold in any climate
This guide states the conditions the plant itself responds to — soil temperature, frost tolerance, day length — rather than dates, because the same calendar month means opposite seasons in the northern and southern hemispheres. Anything genuinely restricted to one part of the world is named as such rather than presented as universal. Written and maintained by our editorial team against international horticultural research and extension sources.
Sketch your exact plot shape, pick your crops, and get a spacing-accurate bed layout with companion pairings and a rotation plan. Spacing, companion pairings and rotation are the same in every climate and both hemispheres — pair the layout it gives you with when to plant to set your own timing from soil temperature.
