When to Plant Rosemary in Philadelphia County, PA
Your May gardening checklist
Your Philadelphia County, Pennsylvania garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.
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.
Philadelphia County, Pennsylvania is in USDA Zone 7b. The average last spring frost is April 16 and the first fall frost is October 24, giving you a growing season of approximately 191 days.
At an elevation of 996 feet, Philadelphia County receives approximately 48.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 93°F, providing good warmth for Rosemary during the growing season.
Philadelphia County Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-6.7
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 Philadelphia County
How your county's soil matches Rosemary's growing requirements.
Soil pH
Your soil pH (5.2–6.7) is more acidic than Rosemary prefers (6.0–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Philadelphia County is excellent for Rosemary — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (4.0%). Annual compost additions will help Rosemary.
How to Plant Rosemary
Succession Planting Rosemary
Sow every 9.1 weeks. Last sowing by Apr 27 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 | — | 3.9" | 0" | ❄️ Dormant |
| Feb | — | 3.7" | 0" | ❄️ Dormant |
| Mar | — | 3.8" | 0" | ❄️ Dormant |
| Apr | 1.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| May | 1.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Jun | 1.3" | 3.9" | 0" | ✅ Rainfall sufficient |
| Jul | 1.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Aug | 1.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Sep | 1.3" | 3.6" | 0" | ✅ Rainfall sufficient |
| Oct | 1.3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Nov | — | 3.3" | 0" | ❄️ Dormant |
| Dec | — | 3.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Philadelphia 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 — Philadelphia County, PA
Rosemary Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 23 | Apr 23 – May 7 |
| Harvest | July 16 | Jul 16 – Dec 3 |
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
0.3"/week · Natural rainfall sufficient
📅 Days to Maturity
80–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 7b
📆 Growing Season
191 days in Philadelphia County
Growing Tips for Rosemary in Philadelphia County
Direct sow Rosemary outdoors after April 16 in Philadelphia County when soil has warmed and frost danger has passed.
Your 191.0-day growing season in Philadelphia 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 Philadelphia County, PA?
Philadelphia County is in Zone 7b with an average last frost of April 16. Plan your Rosemary planting based on this frost date — see the calendar above for exact timing.
What planting zone is Philadelphia County, PA?
Philadelphia County, Pennsylvania is in USDA Hardiness Zone 7b. The average last spring frost is April 16 and first fall frost is October 24.
Your Philadelphia County Garden Planner — Free
A 24-page printable planner built for Philadelphia County (Zone 7b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.