When to Plant Onion in Brazoria County, TX
May in Brazoria County, Texas — your action list
We've pulled the most time-sensitive tasks for Brazoria County, Texas this May and put them front and centre. Tackle them in order.
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Harvest onion as they ripen
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
Before June arrives, get these ready
- 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.
Brazoria County, Texas is in USDA Zone 9b. The average last spring frost is February 12 and the first fall frost is December 8, giving you a growing season of approximately 299 days.
At an elevation of 348 feet, Brazoria County receives approximately 71.8 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 102°F, so Onion may need afternoon shade and extra watering during peak heat. 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.
Brazoria County Soil Profile
Soil Type
Sandy Loam
Soil pH
5.5-6.3
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 Brazoria County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (5.5–6.3) is more acidic than Onion prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
Sandy soil in Brazoria County warms quickly in spring but drains fast. Onion will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is moderate (2.0%). Annual compost additions will help 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 | — | 1.7" | 0" | ❄️ Dormant |
| Feb | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Mar | 4.3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 8.4" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 11.2" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 11.3" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 8" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.7" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 6.6" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 5.1" | 0" | ✅ Rainfall sufficient |
| Nov | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Dec | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in Brazoria 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 — Brazoria County, TX
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 15 | Jan 15 – Jan 29 |
| Transplant Outdoors | February 12 | Feb 12 – Feb 26 |
| Direct Sow | January 22 | Jan 22 – Feb 12 |
| Harvest | May 14 | May 14 – Jul 2 |
| Fall Sowing | October 13 | Oct 13 – Oct 27 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Direct Sow |
| February | Transplant Outdoors Direct Sow |
| March | — |
| April | — |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 9b
📆 Growing Season
299 days in Brazoria County
Growing Tips for Onion in Brazoria County
Direct sow Onion outdoors after February 12 in Brazoria County when soil has warmed and frost danger has passed.
Sandy soil in Brazoria County dries quickly — mulch Onion with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 102°F in Brazoria County, provide afternoon shade for Onion and water deeply in the morning.
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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Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Brazoria County, TX?
Brazoria County is in Zone 9b with an average last frost of February 12. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Brazoria County, TX?
Brazoria County, Texas is in USDA Hardiness Zone 9b. The average last spring frost is February 12 and first fall frost is December 8.
Your Brazoria County Garden Planner — Free
A 24-page printable planner built for Brazoria 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.