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When to plant Potatoes in Cass County, MI

For Cass County, gardeners: plant Potatoes May 6 through May 27 once soil reads 50°F.

When to Plant Potatoes in Cass County, MI

Potatoes
Cass County, Michigan Zone 6a July

Your July planting checklist for Cass County, Michigan

Your garden in Cass County, Michigan is working on a schedule, even when you're not. Here's where you should be this July.

Avg. last frost April 29
Avg. first frost October 17
Soil temp (4") 81°F
Watering Low
Pest pressure High
Daylight 14.8 hrs
  1. Start harvesting potatoes

    This is the payoff month. Bring a basket, bring a friend, and get into the beds.

Looking ahead to August
  • First harvests: potatoes

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Potatoes are a versatile staple crop that produces tubers underground. They come in hundreds of varieties with varying colors, textures, and maturity dates.

Cass County, Michigan is in USDA Zone 6a. The average last spring frost is April 29 and the first fall frost is October 17, giving you a growing season of approximately 171 days.

At an elevation of 1,030 feet, Cass County receives approximately 34.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Potatoes during the growing season.

Cass County, MI (Zone 6a) Moderate season
171 days
Last Spring Frost April 29
171 growing days
First Fall Frost October 17

Cass County Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-7.2

Drainage

Well Drained

Potatoes Planting Risk Windows

Early Start (70% safe) ✓ Fits season (14 days to spare)
Start indoors: Mar 1 Transplant: May 10 🍅 Harvest: Jul 19 – Sep 27
Recommended (50%) ✓ Fits season (17 days to spare)
Start indoors: Mar 4 Transplant: May 13 🍅 Harvest: Jul 22 – Sep 30
Safe Start (90%) ✓ Fits season (9 days to spare)
Start indoors: Mar 24 Transplant: Jun 2 🍅 Harvest: Aug 11 – Oct 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 Cass County

How your county's soil matches Potatoes's growing requirements.

Soil pH

Your soil pH (6.2–7.2) is more alkaline than Potatoes prefers (5.0–6.5). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is excellent (4.9%) — Potatoes will thrive.

How to Plant Potatoes

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Succession Planting Potatoes

2
successive plantings in your 171-day season

Sow every 8 weeks. Last sowing by Jun 19 to harvest before frost.

Potatoes Water Budget

Plant needs
1.0″/week
Rainfall provides
0.8″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 244 gal / 100 sq ft

Monthly Watering Guide for Potatoes

Potatoes needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Potatoes Needs Rainfall You Supplement Action
Jan 1.5" 0" ❄️ Dormant
Feb 1.6" 0" ❄️ Dormant
Mar 2.5" 0" ❄️ Dormant
Apr 4.3" 3.5" 0.8" 💧 Light watering
May 4.3" 3.9" 0.4" 💧 Light watering
Jun 4.3" 4.5" 0" ✅ Rainfall sufficient
Jul 4.3" 3.8" 0.5" 💧 Light watering
Aug 4.3" 3.5" 0.8" 💧 Light watering
Sep 4.3" 3.2" 1.1" 💧 Light watering
Oct 4.3" 2.2" 2.1" 💧 Light watering
Nov 2.1" 0" ❄️ Dormant
Dec 1.8" 0" ❄️ Dormant

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

Potatoes 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.

Potatoes needs ~1,378 GDD — county provides 2,479 GDD Excellent fit

Potatoes Planting Timeline — Cass County, MI

Potatoes Planting Calendar

Activity When Date Range
Start Indoors March 4 Mar 4 – Mar 18
Transplant Outdoors May 13 May 13 – May 27
Direct Sow May 6 May 6 – May 27
Harvest July 22 Jul 22 – Sep 30

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

70–120 days

🧪 Soil pH

Needs 5–6.5 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6a

📆 Growing Season

171 days in Cass County

Growing Tips for Potatoes in Cass County

Direct sow Potatoes outdoors after April 29 in Cass County when soil has warmed and frost danger has passed.

Common pests for Potatoes in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.

General growing tips

Plant seed potatoes (not grocery store potatoes) 4 inches deep in spring. Hill soil around stems as plants grow to prevent greening. Stop watering when plants die back.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Cucumber
  • Squash Summer

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Potatoes in Cass County, MI?

Cass County is in Zone 6a with an average last frost of April 29. Plan your Potatoes planting based on this frost date — see the calendar above for exact timing.

What planting zone is Cass County, MI?

Cass County, Michigan is in USDA Hardiness Zone 6a. The average last spring frost is April 29 and first fall frost is October 17.

When should I plant Potatoes in Cass County, MI?

In Cass County, MI, plant Potatoes after the last frost (around April 29) and before the first frost (around October 17). Best results when soil holds above 50°F.

What growing zone is Cass County, MI for Potatoes?

Cass County sits in USDA Zone 6a. Potatoes grows reliably in zones 3a through 10b, so it's a good fit here.

Can Potatoes grow in Cass County's climate?

Yes — Potatoes grows well in Cass County's temperate climate. Cass County averages a 171-day frost-free season, with last frost around April 29 and first frost around October 17.

🌱

Your Cass County Garden Planner — Free

A 22-page printable planner built for Cass County (Zone 6a). 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 Cass County, MI. Local conditions may vary. Last updated: July 2026.

Sources & credits

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