When to Plant Hyssop in Jefferson County, MT
Your May planting checklist for Jefferson County, Montana
Welcome to May in Zone 5a. These are the moves that will have the biggest impact on your growing season.
June will be here before you know it — start on
- Transplants going out: hyssop
Hyssop is a semi-evergreen perennial herb with intense blue flower spikes that attract bees and butterflies. It has a minty, slightly bitter flavor used in liqueurs and teas.
Jefferson County, Montana is in USDA Zone 5a. The average last spring frost is June 15 and the first fall frost is September 7, giving you a growing season of approximately 84 days.
At an elevation of 7,214 feet, Jefferson County receives approximately 21.5 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Hyssop to ensure they mature before fall.
Jefferson County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.9
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 Jefferson County
How your county's soil matches Hyssop's growing requirements.
Soil pH
Your soil pH (6.4–7.9) is within Hyssop's preferred range (6.0–8.0).
Soil Texture
The loam soil in Jefferson County is excellent for Hyssop — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Hyssop.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Hyssop.
How to Plant Hyssop
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Hyssop
Hyssop 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 | Hyssop Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | — | 2.5" | 0" | ❄️ Dormant |
| Jun | 2.2" | 1.5" | 0.7" | 💧 Light watering |
| Jul | 2.2" | 2" | 0.2" | 💧 Light watering |
| Aug | 2.2" | 2" | 0.2" | 💧 Light watering |
| Sep | 2.2" | 2" | 0.2" | 💧 Light watering |
| Oct | — | 1.8" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Jun–Sep in Jefferson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Hyssop 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.
Hyssop Planting Timeline — Jefferson County, MT
Hyssop Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | June 22 | Jun 22 – Jul 6 |
| Harvest | August 31 | Aug 31 – Nov 2 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | — |
| June | Transplant Outdoors |
| July | Transplant Outdoors |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–90 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 5a
📆 Growing Season
84 days in Jefferson County
Growing Tips for Hyssop in Jefferson County
Direct sow Hyssop outdoors after June 15 in Jefferson County when soil has warmed and frost danger has passed.
Your 84.0-day growing season in Jefferson County is tight for Hyssop (70.0-90.0 days to maturity). Start indoors and choose early-maturing varieties.
Jefferson County receives only 22" of rain annually. Hyssop needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors or direct sow in spring. Prune back in early spring to encourage bushy growth. Hyssop is drought-tolerant once established and thrives in poor soil.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Hyssop in Other Locations
Frequently Asked Questions
When should I plant Hyssop in Jefferson County, MT?
Jefferson County is in Zone 5a with an average last frost of June 15. Plan your Hyssop planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jefferson County, MT?
Jefferson County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is June 15 and first fall frost is September 7.
Your Jefferson County Garden Planner — Free
A 24-page printable planner built for Jefferson County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.