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When to Plant Kai Lan in Franklin County, WA

Franklin County, Washington Zone 7a May

Top priorities for Franklin County, Washington gardeners in May

Your Franklin County, Washington garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost April 13
Avg. first frost October 23
Soil temp (4") 66°F
Watering Critical
Pest pressure Moderate
Daylight 14.8 hrs
  1. Time to start kai lan inside

    Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.

Looking ahead to June
  • First harvests: kai lan

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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.

Franklin County, Washington is in USDA Zone 7a. The average last spring frost is April 13 and the first fall frost is October 23, giving you a growing season of approximately 193 days.

At an elevation of 1,556 feet, Franklin County receives approximately 15.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Kai Lan during the growing season. With low rainfall, drip irrigation is essential for growing Kai Lan successfully. Mulch heavily to conserve soil moisture.

Franklin County, WA (Zone 7a) Moderate season
193 days
Last Spring Frost April 13
193 growing days
First Fall Frost October 23

Franklin County Soil Profile

Soil Type

Silt Loam

Soil pH

5.6-6.6

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (118 days to spare)
Start indoors: Feb 25 Transplant: Apr 1 🍅 Harvest: May 20 – Jun 17
Recommended (50%) ✓ Fits season (116 days to spare)
Start indoors: Mar 9 Transplant: Apr 13 🍅 Harvest: Jun 1 – Jun 29
Safe Start (90%) ✓ Fits season (104 days to spare)
Start indoors: Apr 5 Transplant: May 10 🍅 Harvest: Jun 28 – Jul 26

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 Franklin County

How your county's soil matches Kai Lan's growing requirements.

Soil pH

Your soil pH (5.6–6.6) overlaps with Kai Lan's range (6.0–7.5), though not a perfect match.

Soil Texture

The silt loam soil in Franklin County is excellent for Kai Lan — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (5.5%) — Kai Lan will thrive.

How to Plant Kai Lan

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Kai Lan

5
successive plantings in your 193-day season

Sow every 5.1 weeks. Last sowing by Aug 24 to harvest before frost.

For a dedicated fall crop, sow by Aug 14.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.3″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 1,131 gal / 100 sq ft

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 2.5" 0" ❄️ Dormant
Feb 1.8" 0" ❄️ Dormant
Mar 1.4" 0" ❄️ Dormant
Apr 4.3" 1.2" 3.1" 🚿 Regular watering
May 4.3" 1" 3.3" 🚿 Regular watering
Jun 4.3" 0.6" 3.7" 🚿 Regular watering
Jul 4.3" 0.2" 4.1" 🚿 Regular watering
Aug 4.3" 0.3" 4" 🚿 Regular watering
Sep 4.3" 0.6" 3.7" 🚿 Regular watering
Oct 4.3" 1.2" 3.1" 🚿 Regular watering
Nov 2.2" 0" ❄️ Dormant
Dec 2.7" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Oct in Franklin 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 needs ~919 GDD — county provides 3,377 GDD Excellent fit

Kai Lan Planting Timeline — Franklin County, WA

Kai Lan Planting Calendar

Activity When Date Range
Start Indoors March 9 Mar 9 – Mar 23
Transplant Outdoors April 13 Apr 13 – Apr 27
Direct Sow March 30 Mar 30 – Apr 20
Harvest June 1 Jun 1 – Jun 29
Fall Sowing August 14 Aug 14 – Aug 28

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors Direct Sow
April Transplant Outdoors Direct Sow
May
June Harvest
July
August Fall Sowing
September
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

45–60 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 7a

📆 Growing Season

193 days in Franklin County

Growing Tips for Kai Lan in Franklin County

Direct sow Kai Lan outdoors after April 13 in Franklin County when soil has warmed and frost danger has passed.

Your generous 193.0-day season in Franklin 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.

Franklin County receives only 16" of rain annually. Kai Lan needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

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

  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Kai Lan in Franklin County, WA?

Franklin County is in Zone 7a with an average last frost of April 13. Plan your Kai Lan planting based on this frost date — see the calendar above for exact timing.

What planting zone is Franklin County, WA?

Franklin County, Washington is in USDA Hardiness Zone 7a. The average last spring frost is April 13 and first fall frost is October 23.

🌱

Your Franklin County Garden Planner — Free

A 24-page printable planner built for Franklin County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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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 Franklin County, WA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.