When to plant Watermelon in Saint Augustine, FL
For Watermelon in Saint Augustine, the safe spring window opens around February 9 and closes around March 2. Last expected frost is February 9, first fall frost December 2, giving a 297-day growing season.
When to Plant Watermelon in Saint Augustine, FL
Your July game plan for St. Johns County, Florida
Each item below is timed to St. Johns County, Florida's frost dates and soil temperatures. Skip nothing, stress about nothing.
Watermelon is a sprawling vine crop that produces sweet, juicy fruits in hot weather. Varieties range from personal-sized icebox types to 50-pound giants.
Saint Augustine, Florida is in USDA Zone 9b. The average last spring frost is February 9 and the first fall frost is December 2, giving you a growing season of approximately 296 days.
At an elevation of 57 feet, St. Johns County receives approximately 51.1 inches of rainfall annually with predominantly sand soil. Summer highs average 99°F, so Watermelon may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Watermelon will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Watermelon root diseases.
Saint Augustine Soil Profile
Soil Type
Sand
Soil pH
4.9-6.1
Drainage
Well Drained
Watermelon 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 Saint Augustine
How your county's soil matches Watermelon's growing requirements.
Soil pH
Your soil pH (4.9–6.1) is more acidic than Watermelon prefers (6.0–7.5). Add garden lime to raise pH.
Soil Texture
Sandy soil in St. Johns County warms quickly in spring but drains fast. Watermelon will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is low (1.5%). Add 2-3 inches of compost before planting Watermelon.
How to Plant Watermelon
Succession Planting Watermelon
Sow every 8 weeks. Last sowing by Aug 24 to harvest before frost.
Watermelon Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Watermelon
Watermelon needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Watermelon Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.4" | 0" | ❄️ Dormant |
| Feb | 6.5" | 2.4" | 4.1" | 🚿 Regular watering |
| Mar | 6.5" | 2.8" | 3.7" | 🚿 Regular watering |
| Apr | 6.5" | 2.8" | 3.7" | 🚿 Regular watering |
| May | 6.5" | 3.5" | 3" | 💧 Light watering |
| Jun | 6.5" | 7" | 0" | ✅ Rainfall sufficient |
| Jul | 6.5" | 7.1" | 0" | ✅ Rainfall sufficient |
| Aug | 6.5" | 7.6" | 0" | ✅ Rainfall sufficient |
| Sep | 6.5" | 6.9" | 0" | ✅ Rainfall sufficient |
| Oct | 6.5" | 4.3" | 2.2" | 💧 Light watering |
| Nov | 6.5" | 2.1" | 4.4" | 🚿 Regular watering |
| Dec | 6.5" | 2.3" | 4.2" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in St. Johns County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Watermelon 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.
Watermelon Planting Timeline — Saint Augustine, FL
Watermelon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 12 | Jan 12 – Jan 26 |
| Transplant Outdoors | February 16 | Feb 16 – Mar 2 |
| Direct Sow | February 9 | Feb 9 – Mar 2 |
| Harvest | April 27 | Apr 27 – Jun 15 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Transplant Outdoors Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | Harvest |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.5"/week · 2-3 times/week
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 9b
📆 Growing Season
296 days in St. Johns County
Growing Tips for Watermelon in Saint Augustine
Direct sow Watermelon outdoors after February 09 in St. Johns County when soil has warmed and frost danger has passed.
Sandy soil in St. Johns County dries quickly — mulch Watermelon with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 99°F in St. Johns County, provide afternoon shade for Watermelon and water deeply in the morning.
Common pests for Watermelon in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 3-4 weeks early or direct sow after soil is warm. Plant on mounds with plenty of space. Check ripeness by looking for a yellow ground spot and dull thump when tapped.
Recommended Watermelon Varieties for Saint Augustine
Full-size melons that thrive with your long season
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Watermelon in Other Locations
When should I plant Watermelon in Saint Augustine, FL?
In Saint Augustine, FL, plant Watermelon after the last frost (around February 9) and before the first frost (around December 2). Best results when soil holds above 50°F.
What growing zone is Saint Augustine, FL for Watermelon?
Saint Augustine sits in USDA Zone 9b. Watermelon grows reliably in zones 4a through 11b, so it's a good fit here.
Can Watermelon grow in Saint Augustine's climate?
Yes — Watermelon grows well in Saint Augustine's temperate climate. Saint Augustine averages a 297-day frost-free season, with last frost around February 9 and first frost around December 2.
Your St. Johns County Garden Planner — Free
A 22-page printable planner built for St. Johns County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.