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When to Plant Hubbard Squash in Boone County, IA

Boone County, Iowa Zone 5a May

Your May game plan for Boone 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.

Avg. last frost April 28
Avg. first frost October 6
Soil temp (4") 60°F
Watering Low
Pest pressure Low
Daylight 14.4 hrs
  1. Plant out hubbard squash

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

  2. Outdoor sowing time: hubbard squash

    Your soil is 60°F — warm enough for these to germinate without babying.

Looking ahead to June
  • Starting indoors: hubbard squash

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Hubbard squash is a large, bumpy-skinned winter squash with dense, sweet, dry flesh ideal for baking and pies. The hard shell allows storage for 6 months or more.

Boone County, Iowa is in USDA Zone 5a. The average last spring frost is April 28 and the first fall frost is October 6, giving you a growing season of approximately 161 days.

At an elevation of 950 feet, Boone County receives approximately 30.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Hubbard Squash during the growing season.

Boone County, IA (Zone 5a) Moderate season
161 days
Last Spring Frost April 28
161 growing days
First Fall Frost October 6

Boone County Soil Profile

Soil Type

Silt Loam

Soil pH

6.1-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (5 days to spare)
Start indoors: Mar 18 Transplant: May 6 🍅 Harvest: Aug 19 – Sep 23
Recommended (50%) ✓ Fits season (7 days to spare)
Start indoors: Mar 24 Transplant: May 12 🍅 Harvest: Aug 25 – Sep 29
Safe Start (90%) ✓ Fits season (4 days to spare)
Start indoors: Apr 7 Transplant: May 26 🍅 Harvest: Sep 8 – Oct 13

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 Boone County

How your county's soil matches Hubbard Squash's growing requirements.

Soil pH

Your soil pH (6.1–6.9) is within Hubbard Squash's preferred range (6.0–7.0).

Soil Texture

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

Organic Matter

Organic matter is excellent (4.2%) — Hubbard Squash will thrive.

How to Plant Hubbard Squash

1"
Planting Depth
30"
Between Plants
42"
Between Rows

Plant 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 342 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Hubbard Squash

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

Month Hubbard Squash Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 2" 0" ❄️ Dormant
Apr 4.3" 2.9" 1.4" 💧 Light watering
May 4.3" 3.8" 0.5" 💧 Light watering
Jun 4.3" 3.5" 0.8" 💧 Light watering
Jul 4.3" 3.2" 1.1" 💧 Light watering
Aug 4.3" 3.4" 0.9" 💧 Light watering
Sep 4.3" 2.8" 1.5" 💧 Light watering
Oct 4.3" 2.5" 1.8" 💧 Light watering
Nov 2.2" 0" ❄️ Dormant
Dec 1.7" 0" ❄️ Dormant

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

Hubbard Squash 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.

Hubbard Squash needs ~1,512 GDD — county provides 2,213 GDD Excellent fit

Hubbard Squash Planting Timeline — Boone County, IA

Hubbard Squash Planting Calendar

Activity When Date Range
Start Indoors March 24 Mar 24 – Apr 7
Transplant Outdoors May 12 May 12 – May 26
Direct Sow May 5 May 5 – May 26
Harvest August 25 Aug 25 – Sep 29

Plant 1" deep · 30" apart · Rows 42" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April Start Indoors
May Transplant Outdoors Direct Sow
June
July
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

100–120 days

🧪 Soil pH

Needs 6–7 · Your soil: ideal

🗺️ USDA Zone

Zone 5a

📆 Growing Season

161 days in Boone County

Growing Tips for Hubbard Squash in Boone County

Direct sow Hubbard Squash outdoors after April 28 in Boone County when soil has warmed and frost danger has passed.

Common pests for Hubbard Squash in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Start seeds indoors in short-season areas. Requires ample space and rich soil. Harvest when the skin is very hard and the color is deep. Cure in the sun before storing.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Hubbard Squash in Boone County, IA?

Boone County is in Zone 5a with an average last frost of April 28. Plan your Hubbard Squash planting based on this frost date — see the calendar above for exact timing.

What planting zone is Boone County, IA?

Boone County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 28 and first fall frost is October 6.

🌱

Your Boone County Garden Planner — Free

A 24-page printable planner built for Boone County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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