When to Plant Tatsoi in Boulder County, CO
Your May game plan for Boulder County, Colorado
If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.
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Plant out tatsoi
Your last frost (May 14) has passed. These warm-season crops can handle outdoor soil now.
To set up a strong June, finish these tasks
- Starting indoors: tatsoi
- First harvests: tatsoi
Tatsoi is a compact Asian green forming beautiful rosettes of dark, spoon-shaped leaves with a mild mustard flavor. It is extremely cold-hardy and versatile.
Boulder County, Colorado is in USDA Zone 6a. The average last spring frost is May 14 and the first fall frost is September 26, giving you a growing season of approximately 135 days.
At an elevation of 7,657 feet, Boulder County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Tatsoi during the growing season.
Boulder County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
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 Boulder County
How your county's soil matches Tatsoi's growing requirements.
Soil pH
Your soil pH (6.7–8.0) overlaps with Tatsoi's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Boulder County is excellent for Tatsoi — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Tatsoi.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Tatsoi.
How to Plant Tatsoi
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Tatsoi
Sow every 4 weeks. Last sowing by Aug 07 to harvest before frost.
For a dedicated fall crop, sow by Jul 18.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Tatsoi
Tatsoi needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Tatsoi Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 4.3" | 3" | 1.3" | 💧 Light watering |
| Jun | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Jul | 4.3" | 2" | 2.3" | 🚿 Regular watering |
| Aug | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Sep | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Oct | — | 1.9" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Boulder County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tatsoi 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.
Tatsoi Planting Timeline — Boulder County, CO
Tatsoi Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 9 | Apr 9 – Apr 23 |
| Transplant Outdoors | May 14 | May 14 – May 28 |
| Direct Sow | April 30 | Apr 30 – May 21 |
| Harvest | June 18 | Jun 18 – Jul 23 |
| Fall Sowing | July 18 | Jul 18 – Aug 1 |
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"/week · 2-3 times/week
📅 Days to Maturity
35–50 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 6a
📆 Growing Season
135 days in Boulder County
Growing Tips for Tatsoi in Boulder County
Direct sow Tatsoi outdoors after May 14 in Boulder County when soil has warmed and frost danger has passed.
Your generous 135.0-day season in Boulder County allows multiple plantings of Tatsoi. Sow every 17.0 days for continuous harvest.
Common pests for Tatsoi in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
Boulder County receives only 22" of rain annually. Tatsoi needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow in spring or fall. Tatsoi tolerates frost down to 15F. Harvest outer leaves or cut whole rosettes. Excellent in salads, stir-fries, or lightly wilted.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Tatsoi in Other Locations
Frequently Asked Questions
When should I plant Tatsoi in Boulder County, CO?
Boulder County is in Zone 6a with an average last frost of May 14. Plan your Tatsoi planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boulder County, CO?
Boulder County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 14 and first fall frost is September 26.
Your Boulder County Garden Planner — Free
A 24-page printable planner built for Boulder County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.