When to Plant Basil in Polk County, IA
Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.
Polk County, Iowa is in USDA Zone 5a. The average last spring frost is May 2 and the first fall frost is October 7, giving you a growing season of approximately 158 days.
At an elevation of 1,037 feet, Polk County receives approximately 30.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Basil during the growing season.
Polk County Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.8
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.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Basil Planting Timeline — Polk County, IA
Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 14 | Mar 14 – Mar 28 |
| Transplant Outdoors | May 16 | May 16 – May 30 |
| Direct Sow | May 9 | May 9 – May 30 |
| Harvest | July 11 | Jul 11 – Sep 12 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
50–75 days
Soil pH
6 – 7
USDA Zone
Zone 5a
Growing Season
158 days
Growing Tips for Polk County
Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Isolate 150 ft between varieties. Different basil species can cross.
Basil in Other Locations
Frequently Asked Questions
When should I plant Basil in Polk County, IA?
Polk County is in Zone 5a with an average last frost of May 2. Plan your Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Polk County, IA?
Polk County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is May 2 and first fall frost is October 7.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Polk County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
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