When to plant Rosemary in New Castle County County,
New Castle County County's 208-day season only supports one Rosemary planting per year. Sow between April 13 and April 27 for the best chance at full maturity before October 31.
When to Plant Rosemary in New Castle County, DE
New Castle County, Delaware gardeners: here's your June plan
A quick June briefing for New Castle County, Delaware gardeners — what's urgent, what's next, and what can wait.
July prep starts now
- First harvests: rosemary
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.
New Castle County, Delaware is in USDA Zone 7b. The average last spring frost is April 6 and the first fall frost is October 31, giving you a growing season of approximately 208 days.
At an elevation of 415 feet, New Castle County receives approximately 38.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 89°F, providing good warmth for Rosemary during the growing season.
New Castle County Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-7.1
Drainage
Well Drained
Rosemary 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 New Castle County
How your county's soil matches Rosemary's growing requirements.
Soil pH
Your soil pH (5.2–7.1) overlaps with Rosemary's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in New Castle County is excellent for Rosemary — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Rosemary.
How to Plant Rosemary
Succession Planting Rosemary
Sow every 9.1 weeks. Last sowing by May 04 to harvest before frost.
Rosemary 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 | — | 2.4" | 0" | ❄️ Dormant |
| Feb | — | 2.7" | 0" | ❄️ Dormant |
| Mar | — | 3.4" | 0" | ❄️ Dormant |
| Apr | 1.3" | 3.2" | 0" | ✅ Rainfall sufficient |
| May | 1.3" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jun | 1.3" | 3.3" | 0" | ✅ Rainfall sufficient |
| Jul | 1.3" | 4.1" | 0" | ✅ Rainfall sufficient |
| Aug | 1.3" | 3.2" | 0" | ✅ Rainfall sufficient |
| Sep | 1.3" | 3.1" | 0" | ✅ Rainfall sufficient |
| Oct | 1.3" | 3.2" | 0" | ✅ Rainfall sufficient |
| Nov | — | 3.4" | 0" | ❄️ Dormant |
| Dec | — | 2.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in New Castle 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 — New Castle County, DE
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 · Natural rainfall sufficient
📅 Days to Maturity
80–180 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 7b
📆 Growing Season
208 days in New Castle County
Growing Tips for Rosemary in New Castle County
Direct sow Rosemary outdoors after April 06 in New Castle 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 New Castle County, DE?
New Castle County is in Zone 7b 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 New Castle County, DE?
New Castle County, Delaware is in USDA Hardiness Zone 7b. The average last spring frost is April 6 and first fall frost is October 31.
When should I plant Rosemary in New Castle County County, ?
In New Castle County County, , plant Rosemary after the last frost (around April 6) and before the first frost (around October 31). Best results when soil holds above 50°F.
What growing zone is New Castle County County, for Rosemary?
New Castle County County sits in USDA Zone 7b. Rosemary grows reliably in zones 7a through 10b, so it's a good fit here.
Can Rosemary grow in New Castle County County's climate?
Yes — Rosemary grows well in New Castle County County's temperate climate. New Castle County County averages a 208-day frost-free season, with last frost around April 6 and first frost around October 31.
Your New Castle County Garden Planner — Free
A 22-page printable planner built for New Castle 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.