When to Plant Onion in St. Lucie County, FL
Top priorities for St. Lucie County, Florida gardeners in May
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in St. Lucie County, Florida.
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Bring in the onion
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
June prep starts now
- First harvests: onion
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
St. Lucie County, Florida is in USDA Zone 10a. The average last spring frost is January 29 and the first fall frost is December 16, giving you a growing season of approximately 321 days.
At an elevation of 185 feet, St. Lucie County receives approximately 56.2 inches of rainfall annually with predominantly sand soil. Summer highs average 89°F, providing good warmth for Onion during the growing season. Sandy soil warms quickly in spring — great for early planting — but Onion will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Onion root diseases.
St. Lucie County Soil Profile
Soil Type
Sand
Soil pH
4.8-5.8
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 St. Lucie County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (4.8–5.8) is more acidic than Onion prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
Sandy soil in St. Lucie County warms quickly in spring but drains fast. Onion will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Onion.
Organic Matter
Organic matter is low (1.3%). Add 2-3 inches of compost before planting Onion.
How to Plant Onion
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | 4.3" | 2.3" | 2" | 💧 Light watering |
| Feb | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| Mar | 4.3" | 3.3" | 1" | 💧 Light watering |
| Apr | 4.3" | 2.2" | 2.1" | 💧 Light watering |
| May | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Jun | 4.3" | 8.1" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 9" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.6" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 7.5" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 5" | 0" | ✅ Rainfall sufficient |
| Nov | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Dec | 4.3" | 2.2" | 2.1" | 💧 Light watering |
Water needs are for active growing months only (Jan–Dec in St. Lucie County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion 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.
Onion Planting Timeline — St. Lucie County, FL
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 1 | Jan 1 – Jan 15 |
| Transplant Outdoors | January 29 | Jan 29 – Feb 12 |
| Direct Sow | January 8 | Jan 8 – Jan 29 |
| Harvest | April 30 | Apr 30 – Jun 18 |
| Fall Sowing | October 21 | Oct 21 – Nov 4 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Transplant Outdoors |
| March | — |
| April | Harvest |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | Fall Sowing |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 10a
📆 Growing Season
321 days in St. Lucie County
Growing Tips for Onion in St. Lucie County
Direct sow Onion outdoors after January 29 in St. Lucie County when soil has warmed and frost danger has passed.
Sandy soil in St. Lucie County dries quickly — mulch Onion with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
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Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in St. Lucie County, FL?
St. Lucie County is in Zone 10a with an average last frost of January 29. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Lucie County, FL?
St. Lucie County, Florida is in USDA Hardiness Zone 10a. The average last spring frost is January 29 and first fall frost is December 16.
Your St. Lucie County Garden Planner — Free
A 24-page printable planner built for St. Lucie County (Zone 10a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.