When to Plant Kohlrabi in Maricopa County, AZ
This month in Maricopa County, Arizona
A quick May briefing for Maricopa County, Arizona gardeners — what's urgent, what's next, and what can wait.
Kohlrabi is an unusual brassica that forms a swollen stem above ground with a mild, sweet turnip-like flavor. Both the bulb and tender leaves are edible.
Maricopa County, Arizona is in USDA Zone 9b. The average last spring frost is January 31 and the first fall frost is December 6, giving you a growing season of approximately 309 days.
At an elevation of 4,014 feet, Maricopa County receives approximately 12.5 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 108°F, so Kohlrabi may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Kohlrabi will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Kohlrabi successfully. Mulch heavily to conserve soil moisture.
Maricopa County Soil Profile
Soil Type
Sandy Loam
Soil pH
7.2-8.5
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 Maricopa County
How your county's soil matches Kohlrabi's growing requirements.
Soil pH
Your soil pH (7.2–8.5) is more alkaline than Kohlrabi prefers (6.0–7.5). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Maricopa County warms quickly in spring but drains fast. Kohlrabi will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is low (0.7%). Add 2-3 inches of compost before planting Kohlrabi.
How to Plant Kohlrabi
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Kohlrabi
Sow every 5.1 weeks. Last sowing by Oct 02 to harvest before frost.
For a dedicated fall crop, sow by Oct 11.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Kohlrabi
Kohlrabi needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.
| Month | Kohlrabi Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | 3" | 0.9" | 2.1" | 🚿 Regular watering |
| Feb | 3" | 0.8" | 2.2" | 🚿 Regular watering |
| Mar | 3" | 0.7" | 2.3" | 🚿 Regular watering |
| Apr | 3" | 0.5" | 2.5" | 🚿 Regular watering |
| May | 3" | 0.3" | 2.7" | 🚿 Regular watering |
| Jun | 3" | 0.4" | 2.6" | 🚿 Regular watering |
| Jul | 3" | 2.1" | 0.9" | 💧 Light watering |
| Aug | 3" | 2.3" | 0.7" | 💧 Light watering |
| Sep | 3" | 1.9" | 1.1" | 💧 Light watering |
| Oct | 3" | 1.2" | 1.8" | 🚿 Regular watering |
| Nov | 3" | 0.6" | 2.4" | 🚿 Regular watering |
| Dec | 3" | 0.8" | 2.2" | 🚿 Regular watering |
Water needs are for active growing months only (Jan–Dec in Maricopa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Kohlrabi 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.
Kohlrabi Planting Timeline — Maricopa County, AZ
Kohlrabi Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 3 | Jan 3 – Jan 17 |
| Transplant Outdoors | January 31 | Jan 31 – Feb 14 |
| Direct Sow | January 10 | Jan 10 – Jan 31 |
| Harvest | March 21 | Mar 21 – Apr 25 |
| Fall Sowing | October 11 | Oct 11 – Oct 25 |
Plant 0.5" deep · 4" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Transplant Outdoors |
| March | Harvest |
| April | Harvest |
| May | — |
| June | — |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.7"/week · 1-2 times/week
📅 Days to Maturity
45–65 days
🧪 Soil pH
Needs 6–7.5 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 9b
📆 Growing Season
309 days in Maricopa County
Growing Tips for Kohlrabi in Maricopa County
Direct sow Kohlrabi outdoors after January 31 in Maricopa County when soil has warmed and frost danger has passed.
Sandy soil in Maricopa County dries quickly — mulch Kohlrabi with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 108°F in Maricopa County, provide afternoon shade for Kohlrabi and water deeply in the morning.
Your generous 310.0-day season in Maricopa County allows multiple plantings of Kohlrabi. Sow every 22.0 days for continuous harvest.
Common pests for Kohlrabi 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 bulbs are 2-3 inches in diameter for best texture and flavor. Larger bulbs may become woody and fibrous.
Companion Planting
Good Companions
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Check more plant combinations with our Companion Planting Checker →
Kohlrabi in Other Locations
Frequently Asked Questions
When should I plant Kohlrabi in Maricopa County, AZ?
Maricopa County is in Zone 9b with an average last frost of January 31. Plan your Kohlrabi planting based on this frost date — see the calendar above for exact timing.
What planting zone is Maricopa County, AZ?
Maricopa County, Arizona is in USDA Hardiness Zone 9b. The average last spring frost is January 31 and first fall frost is December 6.
Your Maricopa County Garden Planner — Free
A 24-page printable planner built for Maricopa 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.