How to grow radish
Family Brassicaceae. Hardy to USDA hardiness zone 3a+ (U.S. Department of Agriculture). Full sun. Ready in 22-30 days.
Sun
Full sun
Spacing
1-2 in
Days to harvest
22-30 days
Hardiness
Zone 3a+
What growers actually recorded
Loading zone 7b results…
When to plant radish
- Direct sow: ~-4 weeks after last frost.
Companion plants for radish
Plant with: Carrot, Lettuce, Cucumber.
Avoid near: Hyssop.
Common pests & problems
Flea beetle.
Feeding & fertilizer
N-P-K ratio: High N (10-5-5): heavy feeders
Organic options: Aged manure or compost worked in deep · Blood meal or feather meal side-dress at 3 wks · Fish emulsion every 2 wks
When to feed: Feed heavily every 2-3 weeks. Brassicas want steady nitrogen for tight heads.
Watch for: Pale/yellow leaves = needs N. Loose heads = feed harder next round.
N = nitrogen (leaves), P = phosphorus (roots and flowers), K = potassium (fruit and disease resistance). How to read a fertilizer label →
Grower's tip
Interplant with slow crops (carrots, parsnips). Radishes mark rows and are gone before the others crowd.
When to plant radish in your zone
Free month-by-month sowing and transplanting lists, built from frost dates for your USDA (United States Department of Agriculture) hardiness zone.
Soil & water for radish
Soil & pH
6.5-7.5: near neutral (raises club-root resistance)
Fertile loam with strong drainage. Firm soil beats fluffy for heading brassicas.
Compost 2 in + 1 cup of alfalfa or feather meal per 10 sq ft. Lime if pH is under 6.5. It also blocks club-root.
Watering
1-1.5 in / week, consistent
Ground-level drip. Uneven water during heading = split heads or bolting.
Lift an edge of the row and check soil at 3 inches. If it clings in a damp ball, hold off. If it crumbles, water until the top 6 inches are evenly moist.
Knowing when to harvest
- Shoulder visible at soil surface matches variety size.
- Pull immediately: a few days late = pithy interior.
- Winter radish (daikon, watermelon) tolerate longer time in the ground.
Storing & keeping
Tops off. Crisper 2 weeks. Winter varieties store 2-3 months in a root cellar.
What to expect
Per plant: 1 root
Per sq ft: 36-64 per sq ft
Troubleshooting radish
All tops, no root
Likely cause: Too much shade or nitrogen
What to do: Full sun; low-N compost only.
Cracked or hot radishes
Likely cause: Heat + irregular water
What to do: Grow in cool weather; steady moisture.
Varieties worth growing
Cherry Belle
22-day beginner classic.
French Breakfast
Elongated, mild, ready in 25 days.
Daikon
Fall crop, huge roots, stores for months.
Growing radish in containers
6 in deep for salad radishes; 12 in for daikon.
Nutrition
Sulforaphane, glucosinolates, vitamin K, calcium. Brassicas are the vegetable powerhouse.
Common questions
Why are my radishes hollow?
Left in the ground too long or hit by heat. Pick 22-30 days after sowing.
Where these numbers come from
- USDA Plant Hardiness Zone Map (2023 revision). Zone assignment and the 30-year normals behind every cold-hardiness figure.
- NOAA NCEI 1991-2020 Climate Normals. Frost dates, growing-season length, and the probability bands on both.
- Cornell, UMN, and UC Davis Cooperative Extension crop guides. Spacing, days to maturity, soil pH targets, and per-plant yield ranges.
- USDA FSIS / FDA Produce Safety guidance. Wash, cure, and cold-storage handling numbers.
Ranges are regional guidance, not a promise for your yard. Your own logged results always override the published range.