When to Plant Sorrel in Union County, IA
Union County, Iowa gardeners: here's your May plan
Here's what deserves your attention in Union County, Iowa this month. Everything below is tailored to Zone 5b and timed around your local frost dates.
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Indoor seed-starting week for sorrel
Starting these indoors now means sturdy transplants ready the moment your soil warms up.
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Bring in the sorrel
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
Looking ahead to June
- First harvests: sorrel
Sorrel is a perennial herb with tangy, lemon-flavored arrow-shaped leaves. It is one of the first greens to emerge in spring and is used in soups and salads.
Union County, Iowa is in USDA Zone 5b. The average last spring frost is April 23 and the first fall frost is October 11, giving you a growing season of approximately 171 days.
At an elevation of 1,311 feet, Union County receives approximately 39 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Sorrel to ensure they mature before fall.
Union County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-7.3
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 Union County
How your county's soil matches Sorrel's growing requirements.
Soil pH
Your soil pH (6.3–7.3) overlaps with Sorrel's range (5.5–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Union County is excellent for Sorrel — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.8%) — Sorrel will thrive.
How to Plant Sorrel
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Sorrel
Sow every 4.6 weeks. Last sowing by Aug 12 to harvest before frost.
For a dedicated fall crop, sow by Aug 02.
Plant Water Budget
Monthly Watering Guide for Sorrel
Sorrel needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Sorrel Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 1.8" | 0" | ❄️ Dormant |
| Mar | — | 2.7" | 0" | ❄️ Dormant |
| Apr | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| May | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Jun | 4.3" | 4.7" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Aug | 4.3" | 4" | 0.3" | 💧 Light watering |
| Sep | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Oct | 4.3" | 3" | 1.3" | 💧 Light watering |
| Nov | — | 2.8" | 0" | ❄️ Dormant |
| Dec | — | 2.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Union County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sorrel 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.
Sorrel Planting Timeline — Union County, IA
Sorrel Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 19 | Mar 19 – Apr 2 |
| Transplant Outdoors | April 16 | Apr 16 – Apr 30 |
| Direct Sow | April 9 | Apr 9 – Apr 30 |
| Harvest | May 28 | May 28 – Jul 30 |
| Fall Sowing | August 2 | Aug 2 – Aug 16 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 5.5–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
171 days in Union County
Growing Tips for Sorrel in Union County
Direct sow Sorrel outdoors after April 23 in Union County when soil has warmed and frost danger has passed.
Your generous 171.0-day season in Union County allows multiple plantings of Sorrel. Sow every 20.0 days for continuous harvest.
General growing tips
Direct sow in early spring or fall. Remove flower stalks promptly to encourage leaf production. Divide clumps every 3-4 years. Young leaves have the best flavor.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Sorrel in Other Locations
Frequently Asked Questions
When should I plant Sorrel in Union County, IA?
Union County is in Zone 5b with an average last frost of April 23. Plan your Sorrel planting based on this frost date — see the calendar above for exact timing.
What planting zone is Union County, IA?
Union County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is April 23 and first fall frost is October 11.
Your Union County Garden Planner — Free
A 24-page printable planner built for Union 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.