🌶️When to Plant Radish in USDA Zone 6b (2026 Guide)
The fastest crop in the garden. Ready in under a month. Here is the cool-season planting schedule for radish in zone 6b (covering areas like Washington DC, Lexington KY). All dates are based on 2026 frost data for your zone.
Direct sow
Mar 18
Harvest From
Apr 15
Because radish is a cool-season crop, it tolerates light frost and can go out around Mar 18, before zone 6b's average last frost on Apr 15.
- Type: Cool-season
- Method: Direct sow
- Days to harvest: 28
- Spacing: 2" apart
- Sun: Full sun to part shade
- Zone 6b frost: Apr 15 – Oct 20
- Season length: ~188 days
- Companions: carrot, lettuce, spinach
Growing radish in zone 6b
Zone 6b has an average last spring frost around Apr 15 and a first fall frost around Oct 20, giving roughly 188 frost-free growing days. That window comfortably fits radish's 28-day cycle, with room for a second succession planting if you time it right.
Radish resents transplanting, so direct sow it right in the garden around Mar 18. Give each plant about 2 inches of space in full sun to part shade.
Zone 6b specific growing notes
In zone 6b (Washington DC, Lexington KY), your 188-day growing season means radish should be one of your first spring plantings. Cool-season crops thrive in the mild part of your growing window. Monitor soil temperature — radish germinates best when soil is 40-75°F.
Your first fall frost around Oct 20 means your last possible harvest is roughly late Oct. For a continuous supply, consider succession planting every 2-3 weeks from Mar 18 through mid-season.
Pro tip for radish
Sow thinly—overcrowding causes all leaves and no bulb formation. Thin to 2 inches apart ruthlessly. The thinnings are edible microgreens. For the mildest flavor, harvest promptly once shoulders push above soil.
Troubleshooting radish
Flea beetles chew tiny round holes (shotgun pattern) in leaves. While severe damage stunts root development, light damage is cosmetic. Row cover at sowing completely prevents infestation.
Growing radish in containers
Shallow 4-6 inch deep trays work perfectly—radishes are the easiest container vegetable. One 12-inch windowsill planter produces a fresh batch every month. Great for kids and beginners.
Can you plant radish twice a year?
Absolutely—sow every 2 weeks in spring and again when temperatures cool in late summer. Skip mid-summer (July) in hot zones—radishes bolt and turn woody above 80°F. Fall radishes are sweeter.
Frequently asked questions
When should I plant radish in zone 6b?
Direct sow around Mar 18. Because radish is a cool-season crop, it tolerates light frost and can go out around Mar 18, before zone 6b's average last frost on Apr 15.
How long does radish take to grow in zone 6b?
About 28 days from sowing to first harvest. A Mar 18 planting in zone 6b is typically ready to pick from around Apr 15. Zone 6b has about 188 frost-free days — plenty of time for a second succession planting.
How far apart should I space radish?
Space radish about 2 inches apart in full sun to part shade. This gives each plant enough room for roots to spread and leaves to catch sunlight without competing.
What is the best tip for growing radish?
Sow thinly—overcrowding causes all leaves and no bulb formation. Thin to 2 inches apart ruthlessly. The thinnings are edible microgreens. For the mildest flavor, harvest promptly once shoulders push above soil.
What are common problems with radish and how do I fix them?
Flea beetles chew tiny round holes (shotgun pattern) in leaves. While severe damage stunts root development, light damage is cosmetic. Row cover at sowing completely prevents infestation.
Can I grow radish in a container?
Shallow 4-6 inch deep trays work perfectly—radishes are the easiest container vegetable. One 12-inch windowsill planter produces a fresh batch every month. Great for kids and beginners.
Can I plant a second crop of radish for fall harvest?
Absolutely—sow every 2 weeks in spring and again when temperatures cool in late summer. Skip mid-summer (July) in hot zones—radishes bolt and turn woody above 80°F. Fall radishes are sweeter.
What grows well next to radish?
Good companion plants for radish are carrot, lettuce, spinach. Avoid planting near warm-season crops that compete for space and nutrients. Radish also benefits from crop rotation — do not plant it in the same spot year after year.