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When to Plant Mustard Greens in Union County, AR

Union County, Arkansas Zone 8b May

Your May planting checklist for Union County, Arkansas

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Union County, Arkansas.

Avg. last frost March 22
Avg. first frost November 3
Soil temp (4") 74°F
Watering Low
Pest pressure High
Daylight 13.7 hrs
  1. Bring in the mustard greens

    If you can't use it all right away, check the food-preservation section of your planner.

Coming up in June — start thinking about
  • First harvests: mustard greens

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Mustard greens are fast-growing brassicas with a spicy, peppery kick. They come in green, red, and purple varieties and are excellent cooked or in salads.

Union County, Arkansas is in USDA Zone 8b. The average last spring frost is March 22 and the first fall frost is November 3, giving you a growing season of approximately 226 days.

At an elevation of 508 feet, Union County receives approximately 52 inches of rainfall annually with predominantly silt loam soil. Summer highs average 92°F, providing good warmth for Mustard Greens during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Mustard Greens root diseases.

Union County, AR (Zone 8b) Long season
226 days
Last Spring Frost March 22
226 growing days
First Fall Frost November 3

Union County Soil Profile

Soil Type

Silt Loam

Soil pH

5.8-6.6

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (132 days to spare)
Start indoors: Feb 6 Transplant: Mar 13 🍅 Harvest: Apr 17 – Jun 19
Recommended (50%) ✓ Fits season (128 days to spare)
Start indoors: Feb 15 Transplant: Mar 22 🍅 Harvest: Apr 26 – Jun 28
Safe Start (90%) ✓ Fits season (127 days to spare)
Start indoors: Mar 9 Transplant: Apr 13 🍅 Harvest: May 18 – Jul 20

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 Mustard Greens's growing requirements.

Soil pH

Your soil pH (5.8–6.6) overlaps with Mustard Greens's range (6.0–7.0), though not a perfect match.

Soil Texture

The silt loam soil in Union County is excellent for Mustard Greens — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.7%). Annual compost additions will help Mustard Greens.

How to Plant Mustard Greens

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 Mustard Greens

9
successive plantings in your 226-day season

Sow every 3.4 weeks. Last sowing by Sep 14 to harvest before frost.

For a dedicated fall crop, sow by Aug 25.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
1.0″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

Monthly Watering Guide for Mustard Greens

Mustard Greens needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.

Month Mustard Greens Needs Rainfall You Supplement Action
Jan 4.8" 0" ❄️ Dormant
Feb 4.5" 0" ❄️ Dormant
Mar 3" 4.5" 0" ✅ Rainfall sufficient
Apr 3" 3.9" 0" ✅ Rainfall sufficient
May 3" 4.6" 0" ✅ Rainfall sufficient
Jun 3" 4.4" 0" ✅ Rainfall sufficient
Jul 3" 5.1" 0" ✅ Rainfall sufficient
Aug 3" 5.1" 0" ✅ Rainfall sufficient
Sep 3" 4.2" 0" ✅ Rainfall sufficient
Oct 3" 3.5" 0" ✅ Rainfall sufficient
Nov 3" 3.8" 0" ✅ Rainfall sufficient
Dec 3.6" 0" ❄️ Dormant

Water needs are for active growing months only (Mar–Nov in Union County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Mustard Greens 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.

Mustard Greens needs ~760 GDD — county provides 4,294 GDD Excellent fit

Mustard Greens Planting Timeline — Union County, AR

Mustard Greens Planting Calendar

Activity When Date Range
Start Indoors February 15 Feb 15 – Mar 1
Transplant Outdoors March 22 Mar 22 – Apr 5
Direct Sow March 8 Mar 8 – Mar 29
Harvest April 26 Apr 26 – Jun 28
Fall Sowing August 25 Aug 25 – Sep 8

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

0.7"/week · Natural rainfall sufficient

📅 Days to Maturity

30–50 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 8b

📆 Growing Season

226 days in Union County

Growing Tips for Mustard Greens in Union County

Direct sow Mustard Greens outdoors after March 22 in Union County when soil has warmed and frost danger has passed.

Your generous 226.0-day season in Union County allows multiple plantings of Mustard Greens. Sow every 15.0 days for continuous harvest.

Common pests for Mustard Greens 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 early spring or fall. Harvest young leaves for milder flavor. Plants bolt quickly in heat so grow as a cool-season crop or provide shade.

Companion Planting

Good Companions

Avoid Planting Near

  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Mustard Greens in Union County, AR?

Union County is in Zone 8b with an average last frost of March 22. Plan your Mustard Greens planting based on this frost date — see the calendar above for exact timing.

What planting zone is Union County, AR?

Union County, Arkansas is in USDA Hardiness Zone 8b. The average last spring frost is March 22 and first fall frost is November 3.

🌱

Your Union County Garden Planner — Free

A 24-page printable planner built for Union County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Union County, AR. 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.