When to Plant Watercress in Carbon County, MT
Carbon County, Montana gardeners: here's your May plan
We've pulled the most time-sensitive tasks for Carbon County, Montana this May and put them front and centre. Tackle them in order.
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Plant out watercress
Frost risk is low now in Carbon County, Montana. If you've been covering beds overnight, you can stop.
To set up a strong June, finish these tasks
- Starting indoors: watercress
- First harvests: watercress
Watercress is a semi-aquatic plant with a peppery, tangy flavor rich in vitamins and minerals. It grows naturally along streams and can be cultivated in containers with standing water.
Carbon County, Montana is in USDA Zone 5a. The average last spring frost is May 13 and the first fall frost is September 28, giving you a growing season of approximately 138 days.
At an elevation of 5,849 feet, Carbon County receives approximately 23.3 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Watercress to ensure they mature before fall.
Carbon County Soil Profile
Soil Type
Loam
Soil pH
6.8-8.1
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 Carbon County
How your county's soil matches Watercress's growing requirements.
Soil pH
Your soil pH (6.8–8.1) overlaps with Watercress's range (6.5–7.5), though not a perfect match.
Soil Texture
The loam soil in Carbon County is excellent for Watercress — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Watercress.
How to Plant Watercress
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Watercress
Sow every 4.6 weeks. Last sowing by Jul 30 to harvest before frost.
For a dedicated fall crop, sow by Jul 20.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Watercress
Watercress needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Watercress Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.9" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | — | 2.6" | 0" | ❄️ Dormant |
| May | 6.5" | 2.4" | 4.1" | 🚿 Regular watering |
| Jun | 6.5" | 1.9" | 4.6" | 🚿 Regular watering |
| Jul | 6.5" | 2" | 4.5" | 🚿 Regular watering |
| Aug | 6.5" | 2.2" | 4.3" | 🚿 Regular watering |
| Sep | 6.5" | 1.8" | 4.7" | 🚿 Regular watering |
| Oct | — | 2.2" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Carbon County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Watercress 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.
Watercress Planting Timeline — Carbon County, MT
Watercress Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 8 | Apr 8 – Apr 22 |
| Transplant Outdoors | May 13 | May 13 – May 27 |
| Direct Sow | April 29 | Apr 29 – May 20 |
| Harvest | June 24 | Jun 24 – Jul 29 |
| Fall Sowing | July 20 | Jul 20 – Aug 3 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Fall Sowing Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1.5"/week · 2-3 times/week
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
138 days in Carbon County
Growing Tips for Watercress in Carbon County
Direct sow Watercress outdoors after May 13 in Carbon County when soil has warmed and frost danger has passed.
Common pests for Watercress in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
Carbon County receives only 23" of rain annually. Watercress needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Grow in containers with trays of water kept fresh. Provide partial shade and cool conditions. Harvest stems by cutting above water level. Replace water frequently to prevent stagnation.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Watercress in Other Locations
Frequently Asked Questions
When should I plant Watercress in Carbon County, MT?
Carbon County is in Zone 5a with an average last frost of May 13. Plan your Watercress planting based on this frost date — see the calendar above for exact timing.
What planting zone is Carbon County, MT?
Carbon County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is May 13 and first fall frost is September 28.
Your Carbon County Garden Planner — Free
A 24-page printable planner built for Carbon 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.