When to Plant Radish in Jefferson County, TN
Top priorities for Jefferson County, Tennessee gardeners in May
Welcome to May in Zone 7b. These are the moves that will have the biggest impact on your growing season.
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Bring in the radish
If you can't use it all right away, check the food-preservation section of your planner.
Radishes are one of the fastest-growing vegetables, with some varieties ready in under a month. They come in round, elongated, and large winter types.
Jefferson County, Tennessee is in USDA Zone 7b. The average last spring frost is April 15 and the first fall frost is October 22, giving you a growing season of approximately 190 days.
At an elevation of 3,886 feet, Jefferson County receives approximately 44.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 93°F, providing good warmth for Radish during the growing season.
Jefferson County Soil Profile
Soil Type
Silt Loam
Soil pH
5.4-6.8
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Jefferson County
How your county's soil matches Radish's growing requirements.
Soil pH
Your soil pH (5.4–6.8) overlaps with Radish's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Jefferson County is excellent for Radish — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.2%). Annual compost additions will help Radish.
How to Plant Radish
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Radish
Sow every 2.4 weeks. Last sowing by Sep 17 to harvest before frost.
For a dedicated fall crop, sow by Aug 13.
Plant Water Budget
Monthly Watering Guide for Radish
Radish needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Radish Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 3.4" | 0" | ❄️ Dormant |
| Feb | — | 3.8" | 0" | ❄️ Dormant |
| Mar | — | 4" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.4" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.5" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.9" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 2.8" | 0" | ✅ Rainfall sufficient |
| Nov | — | 3.6" | 0" | ❄️ Dormant |
| Dec | — | 3.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Jefferson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Radish Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Radish Planting Timeline — Jefferson County, TN
Radish Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | April 1 | Apr 1 – Apr 22 |
| Harvest | April 29 | Apr 29 – May 20 |
| Fall Sowing | August 13 | Aug 13 – Aug 27 |
Plant 0.5" deep · 2" apart · Rows 6" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Direct Sow Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
22–35 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 7b
📆 Growing Season
190 days in Jefferson County
Growing Tips for Radish in Jefferson County
Direct sow Radish outdoors after April 15 in Jefferson County when soil has warmed and frost danger has passed.
Summer highs in Jefferson County reach 93°F — grow Radish as a spring or fall crop. Use shade cloth if planting in summer.
Your generous 190.0-day season in Jefferson County allows multiple plantings of Radish. Sow every 11.0 days for continuous harvest.
Common pests for Radish in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow every 1-2 weeks for continuous harvest. Do not transplant. Harvest spring radishes promptly to prevent them from becoming pithy and hot.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Radish in Other Locations
Frequently Asked Questions
When should I plant Radish in Jefferson County, TN?
Jefferson County is in Zone 7b with an average last frost of April 15. Plan your Radish planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jefferson County, TN?
Jefferson County, Tennessee is in USDA Hardiness Zone 7b. The average last spring frost is April 15 and first fall frost is October 22.
Your Jefferson County Garden Planner — Free
A 24-page printable planner built for Jefferson County (Zone 7b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.