When to Plant Tomatoes in Lake County, CO
Tomatoes are the most popular home garden crop, available in thousands of varieties from tiny cherries to massive beefsteaks. They are warm-season plants needing full sun.
Lake County, Colorado is in USDA Zone 4a. The average last spring frost is June 21 and the first fall frost is August 30, giving you a growing season of approximately 70 days.
At an elevation of 7,687 feet, Lake County receives approximately 21.2 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Tomatoes to ensure they mature before fall.
Lake County Soil Profile
Soil Type
Loam
Soil pH
6.6-8.2
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 Lake County
How your county's soil matches Tomatoes's growing requirements.
Soil pH
Your soil pH (6.6–8.2) is more alkaline than Tomatoes prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Lake County is excellent for Tomatoes — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.9%). Annual compost additions will help Tomatoes.
How to Plant Tomatoes
How Much Tomatoes to Grow
For a family of 4, plant approximately 12 tomatoes plants in about 72 sq ft. In Lake County's 70-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Tomatoes
Tomatoes needs approximately 1.2 inches of water per week (5.2" per month). Here's how your county's rainfall compares month by month.
| Month | Tomatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.1" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.1" | 0" | ❄️ Dormant |
| May | — | 2.7" | 0" | ❄️ Dormant |
| Jun | 5.2" | 1.4" | 3.8" | 🚿 Regular watering |
| Jul | 5.2" | 2.1" | 3.1" | 🚿 Regular watering |
| Aug | 5.2" | 2.2" | 3" | 🚿 Regular watering |
| Sep | — | 1.6" | 0" | ❄️ Dormant |
| Oct | — | 2.1" | 0" | ❄️ Dormant |
| Nov | — | 1.6" | 0" | ❄️ Dormant |
| Dec | — | 1.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Jun–Aug in Lake County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tomatoes 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.
Tomatoes Planting Timeline — Lake County, CO
Tomatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 19 | Apr 19 – May 3 |
| Transplant Outdoors | July 12 | Jul 12 – Jul 26 |
| Direct Sow | July 5 | Jul 5 – Jul 26 |
| Harvest | September 13 | Sep 13 – Nov 22 |
Plant 0.5" deep · 24" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors |
| June | — |
| July | Transplant Outdoors Direct Sow |
| August | — |
| September | Harvest |
| October | Harvest |
| November | Harvest |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.2"/week · Natural rainfall sufficient
📅 Days to Maturity
60–85 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 4a
📆 Growing Season
70 days in Lake County
Growing Tips for Tomatoes in Lake County
Direct sow Tomatoes outdoors after June 21 in Lake County when soil has warmed and frost danger has passed.
Your 70.0-day growing season in Lake County is tight for Tomatoes (60.0-85.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Tomatoes in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.
Lake County receives only 21" of rain annually. Tomatoes needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 6-8 weeks before last frost. Bury transplants deep to encourage rooting along the stem. Provide consistent moisture to prevent blossom end rot and cracking.
Recommended Tomatoes Varieties for Lake County
Choose determinate, early-maturing varieties for your short season
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 25 ft between varieties for purity. Use open-pollinated varieties for true-to-type seeds.
Tomatoes in Other Locations
Frequently Asked Questions
When should I plant Tomatoes in Lake County, CO?
Lake County is in Zone 4a with an average last frost of June 21. Plan your Tomatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Lake County, CO?
Lake County, Colorado is in USDA Hardiness Zone 4a. The average last spring frost is June 21 and first fall frost is August 30.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Lake County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.