How to Grow Black Radishes USA
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
When to sow and plant Black Radishes depends on your own frost dates. Check the USA vegetable planting calendar. 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
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
Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.
Get the USA Garden Planner →Instant PDF download · Written for US growing conditions
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 USDA hardiness-zone and frost-date data, with Cooperative Extension sources cited directly where one exists for a crop. 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
Related guides
More from the same group (brassicas & mustards):
Growing advice for your part of the USA
Timing and conditions change a lot inside one country. These guides cover frost dates and growing seasons region by region.
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.