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When to Plant Lemon Balm in Rio Grande County, CO

Lemon balm is a vigorous perennial herb with bright green, lemon-scented leaves. It makes a refreshing tea and is easy to grow but can spread aggressively.

Rio Grande County, Colorado is in USDA Zone 4b. The average last spring frost is May 31 and the first fall frost is September 19, giving you a growing season of approximately 111 days.

At an elevation of 6,254 feet, Rio Grande County receives approximately 15.8 inches of rainfall annually with predominantly loam soil. Summer highs average 80ยฐF, so choose short-season varieties of Lemon Balm to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Lemon Balm successfully. Mulch heavily to conserve soil moisture.

Rio Grande County, CO (Zone 4b) Short season
111 days
Last Spring Frost May 31
111 growing days
First Fall Frost September 19

Rio Grande County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Transplant: Jun 2 🍅 Harvest: Aug 4 – Sep 22
Recommended (50%) ✗ May not fit
Transplant: Jun 7 🍅 Harvest: Aug 9 – Sep 27
Safe Start (90%) ✗ May not fit
Transplant: Jun 21 🍅 Harvest: Aug 23 – Oct 11

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.6″/week
You supply
0.8″/week
Watering frequency 2-3 times/week
Season total 832 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Lemon Balm needs ~650 GDD — county provides 1,110 GDD Excellent fit

Lemon Balm Planting Timeline โ€” Rio Grande County, CO

Lemon Balm Planting Calendar

Activity When Date Range
Transplant Outdoors June 7 Jun 7 โ€“ Jun 21
Harvest August 9 Aug 9 โ€“ Sep 27

Plant 0.5" deep ยท 8" apart ยท Rows 12" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May โ€”
June Transplant Outdoors
July โ€”
August Harvest
September Harvest
October โ€”
November โ€”
December โ€”

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

Moderate โ€” regular watering

Days to Maturity

60โ€“70 days

Soil pH

5.5 โ€“ 7.5

USDA Zone

Zone 4b

Growing Season

111 days

Growing Tips for Rio Grande County

Start from seed, cuttings, or divisions. Contain in pots or use barriers to prevent spreading. Harvest frequently to keep plants bushy and prevent flowering.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Lemon Balm in Rio Grande County, CO?

Rio Grande County is in Zone 4b with an average last frost of May 31. Plan your Lemon Balm planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Rio Grande County, CO?

Rio Grande County, Colorado is in USDA Hardiness Zone 4b. The average last spring frost is May 31 and first fall frost is September 19.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Rio Grande County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Rio Grande County, CO. Local conditions may vary. Last updated: April 2026.