How to Grow Black Radishes
On this page
Black radishes (Raphanus sativus var. niger) — annual grown as a biennial.
The short answer
- Site
- soil pH 6–7
- Biggest risk
- Brassica downy mildew
Core growing advice on this page is checked against named horticultural sources — see References.
Black Radish (Raphanus sativus var. niger)
3 sources cited · Verified
At a Glance
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 6 - 7 |
| 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
Plan your Black Radishes planting
Timing for Black Radishes follows soil temperature and frost, not the calendar date. The Global vegetable planting calendar explains the method. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.
Growing Black Radish in another region
Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.
Sources
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A secondary gardening reference rather than a university or horticultural authority, used only for sowing depth/spacing/timing detail RHS's cultivar page does not cover, not contradicted by it. 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.
-
Mirrors FAO Ecocrop. Fetched and parsed directly for the numeric soil pH range.
These 2 sources are specific to this region. The full list of 3 sources behind this guide (Nature & Garden, Royal Horticultural Society, Useful Tropical Plants) is in the references of our UK guide to black radishes; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
What soil pH do black radishes need?
A pH of about 6–7. 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 3 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.
Get the Global Garden Planner →Instant PDF download · Works in either hemisphere
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 international horticultural research and extension sources. 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.
Related Problem Guides
Last verified 2026-08-29
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Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Keep going
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.