When to Plant Horehound in Napa County, CA
Top priorities for Napa County, California gardeners in May
Welcome to May in Zone 9b. These are the moves that will have the biggest impact on your growing season.
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Collect horehound at their peak
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
To set up a strong June, finish these tasks
- First harvests: horehound
Horehound is a woolly, drought-tolerant perennial herb traditionally used for cough remedies and candy. It has a distinctive bitter, menthol-like flavor.
Napa County, California is in USDA Zone 9b. The average last spring frost is February 26 and the first fall frost is November 26, giving you a growing season of approximately 273 days.
At an elevation of 449 feet, Napa County receives approximately 35 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Horehound during the growing season.
Napa County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.5
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 Napa County
How your county's soil matches Horehound's growing requirements.
Soil pH
Your soil pH (6.7–7.5) is within Horehound's preferred range (6.0–8.0).
Soil Texture
The loam soil in Napa County is excellent for Horehound — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Horehound.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Horehound.
How to Plant Horehound
Succession Planting Horehound
Sow every 8.6 weeks. Last sowing by Aug 28 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Horehound
Horehound 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 | Horehound Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 7.5" | 0" | ❄️ Dormant |
| Feb | 2.2" | 7.8" | 0" | ✅ Rainfall sufficient |
| Mar | 2.2" | 5.8" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 2.3" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 0.8" | 1.4" | 🚿 Regular watering |
| Jun | 2.2" | 0.2" | 2" | 🚿 Regular watering |
| Jul | 2.2" | 0" | 2.2" | 🚿 Regular watering |
| Aug | 2.2" | 0" | 2.2" | 🚿 Regular watering |
| Sep | 2.2" | 0.3" | 1.9" | 🚿 Regular watering |
| Oct | 2.2" | 1.3" | 0.9" | 💧 Light watering |
| Nov | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Dec | — | 5.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Napa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Horehound 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.
Horehound Planting Timeline — Napa County, CA
Horehound Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | March 5 | Mar 5 – Mar 19 |
| Harvest | May 21 | May 21 – Jul 16 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Transplant Outdoors |
| April | — |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Only during dry spells
📅 Days to Maturity
75–90 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 9b
📆 Growing Season
273 days in Napa County
Growing Tips for Horehound in Napa County
Direct sow Horehound outdoors after February 26 in Napa County when soil has warmed and frost danger has passed.
General growing tips
Direct sow or start from divisions. Thrives in poor, dry soil. Harvest stems just before flowering. Deadhead to prevent aggressive self-seeding. Very drought-tolerant once established.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Horehound in Other Locations
Frequently Asked Questions
When should I plant Horehound in Napa County, CA?
Napa County is in Zone 9b with an average last frost of February 26. Plan your Horehound planting based on this frost date — see the calendar above for exact timing.
What planting zone is Napa County, CA?
Napa County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 26 and first fall frost is November 26.
Your Napa County Garden Planner — Free
A 24-page printable planner built for Napa County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.