When to Plant Borage in Mercer County, NJ
Top priorities for Mercer County, New Jersey gardeners in May
If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.
-
Get borage seeds going inside
Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.
-
Basket week: borage
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
A few tasks this May that'll pay off in June
- First harvests: borage
Borage is a self-seeding annual herb with star-shaped blue flowers that attract pollinators. Its leaves have a cucumber-like flavor and the flowers are edible.
Mercer County, New Jersey is in USDA Zone 7a. The average last spring frost is April 12 and the first fall frost is October 29, giving you a growing season of approximately 200 days.
At an elevation of 4 feet, Mercer County receives approximately 45.5 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Borage during the growing season.
Mercer County Soil Profile
Soil Type
Silt Loam
Soil pH
5-6.7
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 Mercer County
How your county's soil matches Borage's growing requirements.
Soil pH
Your soil pH (5.0–6.7) is more acidic than Borage prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Mercer County is excellent for Borage — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (4.0%). Annual compost additions will help Borage.
How to Plant Borage
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Borage
Sow every 5.7 weeks. Last sowing by Aug 30 to harvest before frost.
For a dedicated fall crop, sow by Aug 20.
Plant Water Budget
Monthly Watering Guide for Borage
Borage needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Borage Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 3.1" | 0" | ❄️ Dormant |
| Feb | — | 3.3" | 0" | ❄️ Dormant |
| Mar | — | 4.1" | 0" | ❄️ Dormant |
| Apr | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.8" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.8" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3.8" | 0" | ✅ Rainfall sufficient |
| Nov | — | 3.8" | 0" | ❄️ Dormant |
| Dec | — | 3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Mercer County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Borage 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.
Borage Planting Timeline — Mercer County, NJ
Borage Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 8 | Mar 8 – Mar 22 |
| Transplant Outdoors | April 5 | Apr 5 – Apr 19 |
| Direct Sow | March 29 | Mar 29 – Apr 19 |
| Harvest | May 31 | May 31 – Jul 19 |
| Fall Sowing | August 20 | Aug 20 – Sep 3 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing |
| September | Fall Sowing |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
50–60 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 7a
📆 Growing Season
200 days in Mercer County
Growing Tips for Borage in Mercer County
Direct sow Borage outdoors after April 12 in Mercer County when soil has warmed and frost danger has passed.
General growing tips
Direct sow in spring as borage does not transplant well. Allow some plants to go to seed for next year. Young leaves are best; older leaves become bristly.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Borage in Other Locations
Frequently Asked Questions
When should I plant Borage in Mercer County, NJ?
Mercer County is in Zone 7a with an average last frost of April 12. Plan your Borage planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mercer County, NJ?
Mercer County, New Jersey is in USDA Hardiness Zone 7a. The average last spring frost is April 12 and first fall frost is October 29.
Your Mercer County Garden Planner — Free
A 24-page printable planner built for Mercer 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.