When to Plant Hyssop in Carter County, MT
Carter County, Montana gardeners: here's your May plan
May is a pivotal month for Carter County, Montana gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Harden off and plant hyssop
Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.
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.
Carter County, Montana is in USDA Zone 4b. The average last spring frost is May 15 and the first fall frost is September 22, giving you a growing season of approximately 130 days.
At an elevation of 7,923 feet, Carter County receives approximately 19.8 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Hyssop to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Hyssop successfully. Mulch heavily to conserve soil moisture.
Carter County Soil Profile
Soil Type
Loam
Soil pH
6.4-8.2
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 Carter County
How your county's soil matches Hyssop's growing requirements.
Soil pH
Your soil pH (6.4–8.2) overlaps with Hyssop's range (6.0–8.0), though not a perfect match.
Soil Texture
The loam soil in Carter County is excellent for Hyssop — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.7%). Annual compost additions will help Hyssop.
How to Plant Hyssop
Succession Planting Hyssop
Sow every 8 weeks. Last sowing by Jun 24 to harvest before frost.
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 | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 2" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 2.2" | 2.4" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Jul | 2.2" | 1.6" | 0.6" | 💧 Light watering |
| Aug | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Sep | 2.2" | 1.4" | 0.8" | 💧 Light watering |
| Oct | — | 1.7" | 0" | ❄️ Dormant |
| Nov | — | 1.3" | 0" | ❄️ Dormant |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Carter 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 — Carter County, MT
Hyssop Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 22 | May 22 – Jun 5 |
| Harvest | July 31 | Jul 31 – Oct 2 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| 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: acceptable
🗺️ USDA Zone
Zone 4b
📆 Growing Season
130 days in Carter County
Growing Tips for Hyssop in Carter County
Direct sow Hyssop outdoors after May 15 in Carter County when soil has warmed and frost danger has passed.
Carter County receives only 20" 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 Carter County, MT?
Carter County is in Zone 4b with an average last frost of May 15. Plan your Hyssop planting based on this frost date — see the calendar above for exact timing.
What planting zone is Carter County, MT?
Carter County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 15 and first fall frost is September 22.
Your Carter County Garden Planner — Free
A 24-page printable planner built for Carter County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.