When to Plant Fennel (herb) in Hillsborough County, NH
May to-do list for Hillsborough County, New Hampshire
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Hillsborough County, New Hampshire.
Before June arrives, get these ready
- Starting indoors: fennel (herb)
- First harvests: fennel (herb)
Herb fennel is grown for its aromatic leaves, stalks, and seeds rather than a bulb. It has a strong anise flavor and its flowers attract beneficial insects.
Hillsborough County, New Hampshire is in USDA Zone 6a. The average last spring frost is May 2 and the first fall frost is October 11, giving you a growing season of approximately 162 days.
At an elevation of 145 feet, Hillsborough County receives approximately 44 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Fennel (herb) to ensure they mature before fall.
Hillsborough County Soil Profile
Soil Type
Silt Loam
Soil pH
4.9-6.6
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 Hillsborough County
How your county's soil matches Fennel (herb)'s growing requirements.
Soil pH
Your soil pH (4.9–6.6) overlaps with Fennel (herb)'s range (5.5–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Hillsborough County is excellent for Fennel (herb) — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Fennel (herb).
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Fennel (herb).
How to Plant Fennel (herb)
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Fennel (herb)
Sow every 6.9 weeks. Last sowing by Jul 13 to harvest before frost.
For a dedicated fall crop, sow by Aug 02.
Plant Water Budget
Monthly Watering Guide for Fennel (herb)
Fennel (herb) needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Fennel (herb) Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 3" | 0" | ❄️ Dormant |
| Feb | — | 2.7" | 0" | ❄️ Dormant |
| Mar | — | 3.8" | 0" | ❄️ Dormant |
| Apr | — | 4.4" | 0" | ❄️ Dormant |
| May | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jun | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Jul | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Sep | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Oct | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Nov | — | 3.2" | 0" | ❄️ Dormant |
| Dec | — | 3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Hillsborough County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Fennel (herb) 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.
Fennel (herb) Planting Timeline — Hillsborough County, NH
Fennel (herb) Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 28 | Mar 28 – Apr 11 |
| Transplant Outdoors | April 25 | Apr 25 – May 9 |
| Direct Sow | April 18 | Apr 18 – May 9 |
| Harvest | June 27 | Jun 27 – Sep 5 |
| Fall Sowing | August 2 | Aug 2 – Aug 16 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 5.5–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 6a
📆 Growing Season
162 days in Hillsborough County
Growing Tips for Fennel (herb) in Hillsborough County
Direct sow Fennel (herb) outdoors after May 02 in Hillsborough County when soil has warmed and frost danger has passed.
Common pests for Fennel (herb) in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow in spring or fall. Unlike Florence fennel, herb fennel does not form a bulb. Harvest fronds as needed and seeds when they turn brown. Self-sows readily.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Fennel (herb) in Other Locations
Frequently Asked Questions
When should I plant Fennel (herb) in Hillsborough County, NH?
Hillsborough County is in Zone 6a with an average last frost of May 2. Plan your Fennel (herb) planting based on this frost date — see the calendar above for exact timing.
What planting zone is Hillsborough County, NH?
Hillsborough County, New Hampshire is in USDA Hardiness Zone 6a. The average last spring frost is May 2 and first fall frost is October 11.
Your Hillsborough County Garden Planner — Free
A 24-page printable planner built for Hillsborough County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.