Black Radish (Raphanus sativus var. niger)
2 sources cited · Verified
The short answer
- Site
- 6+ hours of sun, soil pH 5.9–6.8
- Biggest risk
- Brassica downy mildew
Black radishes (Raphanus sativus var. niger) — annual grown as a biennial.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
At a Glance
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 |
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
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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.
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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
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
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.
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