When to Plant Rosemary in Boise County, ID
May to-do list for Boise County, Idaho
Here's what deserves your attention in Boise County, Idaho this month. Everything below is tailored to Zone 7a and timed around your local frost dates.
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Transplant rosemary outside
Bring a watering can to the bed. Each transplant gets a drink the moment it's in the ground, not ten minutes later.
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.
Boise County, Idaho is in USDA Zone 7a. The average last spring frost is May 18 and the first fall frost is September 27, giving you a growing season of approximately 132 days.
At an elevation of 8,023 feet, Boise County receives approximately 24.3 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Rosemary during the growing season.
Boise County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.7
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 Boise County
How your county's soil matches Rosemary's growing requirements.
Soil pH
Your soil pH (6.7–7.7) overlaps with Rosemary's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Boise County is excellent for Rosemary — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Rosemary.
How to Plant Rosemary
Plant Water Budget
Water stress score is 8/10 — 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 | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | — | 2.4" | 0" | ❄️ Dormant |
| May | 1.3" | 3" | 0" | ✅ Rainfall sufficient |
| Jun | 1.3" | 1.9" | 0" | ✅ Rainfall sufficient |
| Jul | 1.3" | 1.8" | 0" | ✅ Rainfall sufficient |
| Aug | 1.3" | 2.8" | 0" | ✅ Rainfall sufficient |
| Sep | 1.3" | 1.7" | 0" | ✅ Rainfall sufficient |
| Oct | — | 2.4" | 0" | ❄️ Dormant |
| Nov | — | 1.5" | 0" | ❄️ Dormant |
| Dec | — | 1.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Boise 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 — Boise County, ID
Rosemary Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 25 | May 25 – Jun 8 |
| Harvest | August 17 | Aug 17 – Jan 4 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Harvest |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | — |
| 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
132 days in Boise County
Growing Tips for Rosemary in Boise County
Direct sow Rosemary outdoors after May 18 in Boise County when soil has warmed and frost danger has passed.
Your 132.0-day growing season in Boise 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 Boise County, ID?
Boise County is in Zone 7a with an average last frost of May 18. Plan your Rosemary planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boise County, ID?
Boise County, Idaho is in USDA Hardiness Zone 7a. The average last spring frost is May 18 and first fall frost is September 27.
Your Boise County Garden Planner — Free
A 24-page printable planner built for Boise 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.