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How to Grow Mashuas UK | Regional Planting Calendar
Move through the SoilCommander growing library like a course: keep the navigation in place, open the next lesson, and build your garden plan step by step.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from early May in Southern England to mid May in Scotland.
Core growing advice on this page is checked against named horticultural sources — see References.
Cultivariable states planting is done after frost danger passes; taken here as May for southern England.
Midlands - detail & sources
Same after-frost planting window as elsewhere in the UK.
Northern England - detail & sources
Planting window opens about a week later than southern England for a later last-frost date -- RHS rates 'Ken Aslet' H3, only reliably hardy in coastal and relatively mild UK areas, so exposed northern sites may do better with container growing and indoor overwintering.
Scotland - detail & sources
Planting window opens about two weeks later than southern England for Scotland's later last-frost date -- RHS's H3 rating makes reliable outdoor overwintering unlikely here, so lifting tubers or growing in a movable container is the safer approach.
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).
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.
'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
When should I sow mashuas in the UK?
In Southern England, from early May. In Scotland, wait until mid May. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.
When do I sow mashuas?
Sow early May to early June.
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
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.
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.
Sketch your exact plot shape, pick your UK crops, and get a spacing-accurate bed layout with companion pairings, a rotation plan and month-by-month sowing dates — every fact sourced from RHS and Garden Organic.
