When to Plant Kai Lan in Napa County, CA
May in Napa County, California — your action list
Your garden in Napa County, California is working on a schedule, even when you're not. Here's where you should be this May.
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Collect kai lan at their peak
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
Kai lan (Chinese broccoli) is a brassica grown for its thick, glossy stems and small flower buds. It has a slightly bitter, broccoli-like flavor essential in Cantonese cooking.
Napa County, California is in USDA Zone 9b. The average last spring frost is February 26 and the first fall frost is November 26, giving you a growing season of approximately 273 days.
At an elevation of 449 feet, Napa County receives approximately 35 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Kai Lan during the growing season.
Napa County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.5
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 Napa County
How your county's soil matches Kai Lan's growing requirements.
Soil pH
Your soil pH (6.7–7.5) is within Kai Lan's preferred range (6.0–7.5).
Soil Texture
The loam soil in Napa County is excellent for Kai Lan — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Kai Lan.
Organic Matter
Organic matter is moderate (3.0%). Annual compost additions will help Kai Lan.
How to Plant Kai Lan
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Kai Lan
Sow every 5.1 weeks. Last sowing by Sep 27 to harvest before frost.
For a dedicated fall crop, sow by Oct 01.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Kai Lan
Kai Lan needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Kai Lan Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 7.5" | 0" | ❄️ Dormant |
| Feb | 4.3" | 7.8" | 0" | ✅ Rainfall sufficient |
| Mar | 4.3" | 5.8" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 2.3" | 2" | 💧 Light watering |
| May | 4.3" | 0.8" | 3.5" | 🚿 Regular watering |
| Jun | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Jul | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Aug | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Sep | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Oct | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Nov | 4.3" | 3.3" | 1" | 💧 Light watering |
| Dec | — | 5.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in Napa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Kai Lan 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.
Kai Lan Planting Timeline — Napa County, CA
Kai Lan Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 29 | Jan 29 – Feb 12 |
| Transplant Outdoors | February 26 | Feb 26 – Mar 12 |
| Direct Sow | February 5 | Feb 5 – Feb 26 |
| Harvest | April 16 | Apr 16 – May 14 |
| Fall Sowing | October 1 | Oct 1 – Oct 15 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | Start Indoors Transplant Outdoors Direct Sow |
| March | Transplant Outdoors |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
45–60 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 9b
📆 Growing Season
273 days in Napa County
Growing Tips for Kai Lan in Napa County
Direct sow Kai Lan outdoors after February 26 in Napa County when soil has warmed and frost danger has passed.
Your generous 274.0-day season in Napa County allows multiple plantings of Kai Lan. Sow every 22.0 days for continuous harvest.
Common pests for Kai Lan in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow in spring or fall. Harvest when flower buds first appear but before they open. Cut stems at the base to encourage side shoots. Prefers cool weather.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Kai Lan in Other Locations
Frequently Asked Questions
When should I plant Kai Lan in Napa County, CA?
Napa County is in Zone 9b with an average last frost of February 26. Plan your Kai Lan planting based on this frost date — see the calendar above for exact timing.
What planting zone is Napa County, CA?
Napa County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 26 and first fall frost is November 26.
Your Napa County Garden Planner — Free
A 24-page printable planner built for Napa County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.