When to Plant Radishes in St. Petersburg, FL
Published: April 24, 2026
Radish Planting Dates for St. Petersburg, FL
| Start seeds indoors | Year-round |
| Last frost (average) | January 15 |
| Direct sow outdoors | December 11–21 |
| Minimum soil temperature | 40°F |
| Expect first harvest | January 2 – January 10 |
| Fall crop planting | November 26–December 6 |
| Fall crop harvest | December 18 |
| First fall frost (average) | December 31 |
⚠ Direct sow radishes 4–6 weeks before last frost — one of the fastest crops in the garden. Ready in as little as 22 days. Succession plant every 2 weeks for continuous harvest.
Best Radish Varieties for St. Petersburg, FL
Consult a St. Petersburg-area nursery or your state extension office for radish varieties proven in Zone 9b.
Growing Radishes in St. Petersburg
St. Petersburg sits in Zone 9b, with an average last frost of January 15 and first fall frost around December 31 — giving a 350-day frost-free growing season. Cool-season crops like radish benefit from St. Petersburg's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
In St. Petersburg's warm climate, radish works best as a fall, winter, and early-spring crop. Summer heat bolts most cool-season vegetables before they can produce a harvestable head or root. Plan primary plantings in October through February in St. Petersburg, not April through June.
St. Petersburg's sandy soils drain fast — St. Petersburg gardeners should water radish more frequently (every 2 to 3 days during peak summer) and add generous compost to improve moisture retention. Raised beds with amended soil perform significantly better than in-ground planting in sandy conditions. Target 1 inches of total water per week, split across several irrigation sessions rather than one deep soaking.
Radish Calendar for St. Petersburg
| Month | Task |
|---|---|
| Year | Start seeds indoors under grow lights |
| January | Last frost — soil warming, prepare bed |
| December | Direct sow seeds into warm soil |
| January | Expect first harvest window to open |
| November | Start fall crop — transplants or direct sow |
| December | First fall frost — harvest remaining, end of outdoor season |
Radish Tips for St. Petersburg Gardeners
- •Thin to 2-inch spacing when seedlings are an inch tall — crowded radishes produce small woody roots.
- •Succession plant every 10–14 days from early spring through late spring for continuous harvest.
- •Plant cool-season radish in St. Petersburg during October through February — spring plantings bolt before producing a usable crop in warm zones.
Common Radish Pests in St. Petersburg
- •Flea Beetle — peaks June–August in Zone 9b (active March–October); tiny black beetles that riddle leaves with holes; row covers protect seedlings.
- •Cabbage Root Maggot — peaks June–August in Zone 9b (active March–October); monitor closely during peak season and treat early.
- •Aphid — peaks June–August in Zone 9b (active March–October); monitor closely during peak season and treat early.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Radishes in St. Petersburg
In St. Petersburg's warm climate, Lettuce and Carrot are the most beneficial plants to grow alongside radish. Lettuce improves nearby plant health and pest resistance. Keep radish away from Hyssop — it competes for nutrients or shares pest pressure. Warm-climate gardeners especially benefit from dense, layered companion plantings that shade soil and reduce water loss.
Frequently Asked Questions
When should I plant radish in St. Petersburg, FL?
In St. Petersburg (Zone 9b), direct sow radish around December 11–21. Soil must be at 40°F or warmer at 2-inch depth before sowing — cold soil rots the seeds.
What zone is St. Petersburg, FL for radish growing?
St. Petersburg is USDA Zone 9b. For radish, this means a frost-free growing season of roughly 50 weeks running from January 15 to December 31. Cool-season crops like radish thrive in this zone with both spring and fall planting windows available.
When is radish harvest season in St. Petersburg?
Expect the first radish harvest in St. Petersburg around January 2, with harvest continuing through January 10. This is based on 22–30 days from transplant or direct sow. A fall crop planted November 26–December 6 adds a second harvest around December 18.
How long does it take to grow radish in St. Petersburg, FL?
From transplant or direct sow to first harvest, radish takes 22–30 days in St. Petersburg's climate. Based on a typical planting date of December 11–21, expect your first harvest around January 2. St. Petersburg's warm Zone 9b climate tends toward the faster end of this range — warmer soil and longer days accelerate maturity.
What soil does radish need in St. Petersburg?
St. Petersburg's sandy soils drain fast and lose nutrients quickly — a challenge for radish which prefers steady moisture. Add 4–6 inches of compost annually to improve moisture retention. Water more frequently but with less volume per session, and mulch heavily to reduce evaporation.