When to Plant Rosemary in Grant County, WA
This month in Grant County, Washington
May is a pivotal month for Grant County, Washington gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Transplant rosemary outside
Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.
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.
Grant County, Washington is in USDA Zone 7a. The average last spring frost is April 29 and the first fall frost is October 10, giving you a growing season of approximately 164 days.
At an elevation of 3,122 feet, Grant County receives approximately 17.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 91°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.
Grant County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-6.8
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.
Soil Compatibility in Grant County
How your county's soil matches Rosemary's growing requirements.
Soil pH
Your soil pH (5.6–6.8) overlaps with Rosemary's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Grant County is excellent for Rosemary — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.7%) — Rosemary will thrive.
How to Plant Rosemary
Succession Planting Rosemary
Sow every 9.1 weeks. Last sowing by Apr 13 to harvest before frost.
Plant Water Budget
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 | — | 2.7" | 0" | ❄️ Dormant |
| Feb | — | 1.8" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | 1.3" | 1.5" | 0" | ✅ Rainfall sufficient |
| May | 1.3" | 1.1" | 0.2" | 💧 Light watering |
| Jun | 1.3" | 0.7" | 0.6" | 💧 Light watering |
| Jul | 1.3" | 0.2" | 1.1" | 🚿 Regular watering |
| Aug | 1.3" | 0.4" | 0.9" | 🚿 Regular watering |
| Sep | 1.3" | 0.6" | 0.7" | 🚿 Regular watering |
| Oct | 1.3" | 1.7" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.5" | 0" | ❄️ Dormant |
| Dec | — | 2.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Grant 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 — Grant County, WA
Rosemary Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 6 | May 6 – May 20 |
| Harvest | July 29 | Jul 29 – Dec 16 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| 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
0.3"/week · Natural rainfall sufficient
📅 Days to Maturity
80–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
164 days in Grant County
Growing Tips for Rosemary in Grant County
Direct sow Rosemary outdoors after April 29 in Grant County when soil has warmed and frost danger has passed.
Your 164.0-day growing season in Grant County is tight for Rosemary (80.0-180.0 days to maturity). Start indoors and choose early-maturing varieties.
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 Grant County, WA?
Grant County is in Zone 7a with an average last frost of April 29. Plan your Rosemary planting based on this frost date — see the calendar above for exact timing.
What planting zone is Grant County, WA?
Grant County, Washington is in USDA Hardiness Zone 7a. The average last spring frost is April 29 and first fall frost is October 10.
Your Grant County Garden Planner — Free
A 24-page printable planner built for Grant County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.