When to Plant Rosemary in Washington County, UT
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.
Washington County, Utah is in USDA Zone 8a. The average last spring frost is April 6 and the first fall frost is November 1, giving you a growing season of approximately 209 days.
At an elevation of 3,524 feet, Washington County receives approximately 12.7 inches of rainfall annually with predominantly loam soil. Summer highs average 90°F, providing good warmth for Rosemary during the growing season. With low rainfall, drip irrigation is essential for growing Rosemary successfully. Mulch heavily to conserve soil moisture.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
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 Washington County
How your county's soil matches Rosemary's growing requirements.
Soil pH
Your soil pH (6.7–8.0) overlaps with Rosemary's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Washington County is excellent for Rosemary — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Rosemary.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Rosemary.
How to Plant Rosemary
Succession Planting Rosemary
Sow every 9.1 weeks. Last sowing by May 05 to harvest before frost.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Rosemary
Rosemary needs approximately 0.3 inches of water per week (1.3" per month). Here's how your county's rainfall compares month by month.
| Month | Rosemary Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1" | 0" | ❄️ Dormant |
| Feb | — | 0.6" | 0" | ❄️ Dormant |
| Mar | — | 1.1" | 0" | ❄️ Dormant |
| Apr | 1.3" | 1.2" | 0.1" | 💧 Light watering |
| May | 1.3" | 1.4" | 0" | ✅ Rainfall sufficient |
| Jun | 1.3" | 0.9" | 0.4" | 💧 Light watering |
| Jul | 1.3" | 1.2" | 0.1" | 💧 Light watering |
| Aug | 1.3" | 1.4" | 0" | ✅ Rainfall sufficient |
| Sep | 1.3" | 0.9" | 0.4" | 💧 Light watering |
| Oct | 1.3" | 1.2" | 0.1" | 💧 Light watering |
| Nov | 1.3" | 1" | 0.3" | 💧 Light watering |
| Dec | — | 0.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Washington County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Rosemary 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.
Rosemary Planting Timeline — Washington County, UT
Rosemary Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 13 | Apr 13 – Apr 27 |
| Harvest | July 6 | Jul 6 – Nov 23 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | — |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.3"/week · Only during dry spells
📅 Days to Maturity
80–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 8a
📆 Growing Season
209 days in Washington County
Growing Tips for Rosemary in Washington County
Direct sow Rosemary outdoors after April 06 in Washington County when soil has warmed and frost danger has passed.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Rosemary in Other Locations
Frequently Asked Questions
When should I plant Rosemary in Washington County, UT?
Washington County is in Zone 8a with an average last frost of April 6. Plan your Rosemary planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, UT?
Washington County, Utah is in USDA Hardiness Zone 8a. The average last spring frost is April 6 and first fall frost is November 1.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Washington County gardeners in Zone 8a organize planting dates, track what's growing, and never miss a planting window.
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