When to Plant Rosemary in Benton County, OR
Rosemary is an aromatic evergreen shrub with needle-like leaves and a piney, citrus flavor. It is a Mediterranean herb that thrives in warm, dry conditions.
Benton County, Oregon is in USDA Zone 8a. The average last spring frost is April 14 and the first fall frost is October 30, giving you a growing season of approximately 199 days.
At an elevation of 97 feet, Benton County receives approximately 53.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Rosemary during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Rosemary root diseases.
Benton County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-6.2
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
Rosemary Planting Timeline — Benton County, OR
Rosemary Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 21 | Apr 21 – May 5 |
| Harvest | July 14 | Jul 14 – Dec 1 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | Harvest |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Low — drought tolerant
Days to Maturity
80–180 days
Soil pH
6 – 7.5
USDA Zone
Zone 8a
Growing Season
199 days
Growing Tips for Benton County
Grow in well-drained soil and avoid overwatering. In cold climates, grow in containers and bring indoors for winter. Propagate from stem cuttings for faster results than seed.
Companion Planting
Good Companions
Level Up Your Garden
Rosemary in Other Locations
Frequently Asked Questions
When should I plant Rosemary in Benton County, OR?
Benton County is in Zone 8a with an average last frost of April 14. Plan your Rosemary planting based on this frost date — see the calendar above for exact timing.
What planting zone is Benton County, OR?
Benton County, Oregon is in USDA Hardiness Zone 8a. The average last spring frost is April 14 and first fall frost is October 30.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Benton County gardeners in Zone 8a organize planting dates, track what's growing, and never miss a planting window.
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