Black Radish (Raphanus sativus var. niger)
2 sources cited · Verified
The short answer
- Plant
- Early May to early October
- Site
- 6+ hours of sun, soil pH 5.9–6.8
- Biggest risk
- Brassica downy mildew
In the UK, black radishes go in the ground early May to early October.
Black radishes (Raphanus sativus var. niger) — annual grown as a biennial.
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 early May in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Regional Planting Calendar
| Region | Sow |
|---|---|
| Southern England | early May to early October |
| Midlands | early May to early October |
| Northern England | early May to early October |
| Scotland | early May to early October |
Southern England - detail & sources
Nature & Garden gives a May-to-September/October sowing window depending on climate rather than UK-region-specific dates; this window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Midlands - detail & sources
Nature & Garden gives a May-to-September/October sowing window depending on climate rather than UK-region-specific dates; this window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Northern England - detail & sources
Nature & Garden gives a May-to-September/October sowing window depending on climate rather than UK-region-specific dates; this window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Scotland - detail & sources
Nature & Garden gives a May-to-September/October sowing window depending on climate rather than UK-region-specific dates; this window is applied across all four sub-regions rather than inventing a north/south gradient the source does not support.
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 5.9 - 6.8 |
| Sunlight | 6-6 hours direct sun |
| Soil texture | chalk, clay, loam or sand; loamy, rich in organic matter (RHS, Nature & Garden) |
| Drainage | well-drained |
| Lifecycle | annual grown as a biennial |
| Edible parts | root |
At a Glance
Soil & Growing Conditions
Water: moist but well-drained, moisture-retentive (RHS)
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Sowing | 0 | Sow directly where the plants are to grow, 1/2-1in deep, May to September/October depending on climate (Nature & Garden). |
| Thinning | 3 | Space 2-4in apart, or further for larger roots; avoid excess nitrogen, which favours leaves over root (Nature & Garden). |
| Root development | 4 | Slow-maturing root, taking two to three times longer than common red radish; full sun, moisture-retentive well-drained soil (RHS, Nature & Garden). |
| Harvest | 8 | Harvest in autumn before the first frost (RHS, Nature & Garden). |
Harvest & Storage
When to pick: Harvest in autumn, before the first frost; takes two to three times longer to mature than common red radish (RHS, Nature & Garden).
Diseases
Pests
Black Radish, Sowing to Harvest
References
-
Sow directly where the plants are to grow, in furrows 1/2 to 1 inch (2-3cm) deep, from May to September/October depending on climate. Space 2-4 inches (5-10cm) apart, further for larger radishes. Soil pH ideally 5.9-6.8, well-drained and loamy, rich in organic matter, 6-8 hours of sun daily. Takes about two to three times longer to mature than common red radish; harvest before the first frost. Avoid excess organic material, manure or high-nitrogen fertiliser, which encourages lush foliage at the expense of the root.
-
Late-maturing heritage variety with round black skin and white interior flesh. Hardiness H2 (tolerates low temperatures but cannot survive freezing, 1-5C minimum). Full sun. Soil: chalk, clay, loam or sand; moist but well-drained; acid, alkaline or neutral pH; moisture-retentive soil that isn't overly acidic. Maximum height up to 10cm, spread 0.1-0.5m. Time to maturity 1 year (grown as an annual biennial). Quick to harvest and fits well into limited garden spaces. Harvest available in autumn, reflecting its late-maturing classification. Grow from seed. No pruning needed. PESTS: susceptible to slugs, snails, and flea beetles. DISEASES: may develop brassica downy mildew -- named directly for this variety, not inferred.
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 black radishes in the UK?
In Southern England, from early May. In Scotland, wait until early 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 black radishes?
Sow early May to early October.
What soil pH do black radishes need?
A pH of about 5.9–6.8. 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.
What problems affect black radishes?
Our data links 1 disease 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
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
Last verified 2026-08-29
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
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.