When to Plant Komatsuna in Iowa County, IA
May to-do list for Iowa County, Iowa
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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Start komatsuna indoors
A seed-starting mix and a sunny window (or a grow light) are all you need. Keep soil warm — around 70°F — for fast germination.
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Bring in the komatsuna
This is the payoff month. Bring a basket, bring a friend, and get into the beds.
June will be here before you know it — start on
- First harvests: komatsuna
Komatsuna (Japanese mustard spinach) is a versatile Asian green with glossy, dark leaves and a mild, sweet flavor. It is extremely cold-hardy and heat-tolerant.
Iowa County, Iowa is in USDA Zone 5b. The average last spring frost is April 25 and the first fall frost is October 11, giving you a growing season of approximately 169 days.
At an elevation of 1,014 feet, Iowa County receives approximately 40.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Komatsuna during the growing season.
Iowa County Soil Profile
Soil Type
Silt Loam
Soil pH
6.1-7.3
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 Iowa County
How your county's soil matches Komatsuna's growing requirements.
Soil pH
Your soil pH (6.1–7.3) is within Komatsuna's preferred range (6.0–7.5).
Soil Texture
The silt loam soil in Iowa County is excellent for Komatsuna — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Komatsuna.
Organic Matter
Organic matter is excellent (4.7%) — Komatsuna will thrive.
How to Plant Komatsuna
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Komatsuna
Sow every 4 weeks. Last sowing by Aug 22 to harvest before frost.
For a dedicated fall crop, sow by Aug 02.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Komatsuna
Komatsuna needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Komatsuna Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.9" | 0" | ❄️ Dormant |
| Feb | — | 1.7" | 0" | ❄️ Dormant |
| Mar | — | 3.1" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| May | 4.3" | 5" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.6" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Sep | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| Oct | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Iowa County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Komatsuna 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.
Komatsuna Planting Timeline — Iowa County, IA
Komatsuna Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 21 | Mar 21 – Apr 4 |
| Transplant Outdoors | April 25 | Apr 25 – May 9 |
| Direct Sow | April 11 | Apr 11 – May 2 |
| Harvest | May 30 | May 30 – Jul 4 |
| Fall Sowing | August 2 | Aug 2 – Aug 16 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow Harvest |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
35–50 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
169 days in Iowa County
Growing Tips for Komatsuna in Iowa County
Direct sow Komatsuna outdoors after April 25 in Iowa County when soil has warmed and frost danger has passed.
Your generous 169.0-day season in Iowa County allows multiple plantings of Komatsuna. Sow every 17.0 days for continuous harvest.
Common pests for Komatsuna 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. One of the most forgiving Asian greens for all seasons. Harvest outer leaves or cut whole plants. Excellent for stir-fries, soups, or salads.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Komatsuna in Other Locations
Frequently Asked Questions
When should I plant Komatsuna in Iowa County, IA?
Iowa County is in Zone 5b with an average last frost of April 25. Plan your Komatsuna planting based on this frost date — see the calendar above for exact timing.
What planting zone is Iowa County, IA?
Iowa County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 25 and first fall frost is October 11.
Your Iowa County Garden Planner — Free
A 24-page printable planner built for Iowa County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.