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The best time to plant squash in Illinois is from late May to early June for most varieties.
However, the exact timing depends on whether you’re planting summer squash or winter squash and where you are in the state.
If you’re wondering when to plant squash in Illinois, the short answer is after the last frost date, when the soil has warmed up consistently.
In this post, we’ll cover when to plant squash in Illinois, how to prepare your soil, and tips for growing healthy squash all season long.
Let’s dig in.
When to Plant Squash in Illinois
When to plant squash in Illinois comes down to two main factors: your USDA hardiness zone and the type of squash you’re growing.
Illinois spans zones 5a to 7a, which means planting times vary slightly depending on where you live.
Here’s what you need to know.
1. Wait for the Last Frost Date
Squash is a warm-season crop that hates cold soil.
In Illinois, the last frost date typically falls between mid-April and mid-May, depending on your region.
Northern Illinois gardeners should wait until late May, while those in southern Illinois can often plant by mid-May.
If you plant squash in Illinois too early, the seeds may rot in cold, wet soil or the seedlings may struggle.
2. Check Soil Temperature
The ideal soil temperature for planting squash in Illinois is at least 60°F, with 70°F being even better.
You can use a soil thermometer to check, or simply wait until nighttime temperatures consistently stay above 50°F.
Warm soil helps squash seeds germinate quickly and prevents damping-off disease.
3. Summer Squash vs. Winter Squash
Summer squash like zucchini and yellow crookneck can be planted in Illinois from late May through early July.
Winter squash like butternut and acorn needs a longer growing season, so plant it in Illinois by early June at the latest.
If you’re planting squash in Illinois for a fall harvest, you can sow seeds in early July for summer varieties.
How to Plant Squash in Illinois
Once you know when to plant squash in Illinois, the next step is getting it in the ground the right way.
Here’s how to give your squash the best start.
1. Choose the Right Spot
Squash needs full sun, at least 6 to 8 hours a day.
Pick a spot with well-draining soil rich in organic matter.
If you’re planting squash in Illinois, raised beds or hills work great because they warm up faster in spring.
2. Prepare the Soil
Mix in plenty of compost or aged manure before planting squash in Illinois.
Squash is a heavy feeder and loves fertile soil.
A soil pH between 6.0 and 6.8 is ideal.
3. Plant Seeds or Transplants
You can direct sow squash seeds in Illinois about 1 inch deep, spacing them 2 to 3 feet apart.
If you started seeds indoors, harden them off before transplanting.
When planting squash in Illinois, wait until seedlings have at least two true leaves before moving them outside.
Tips for Growing Squash in Illinois
Planting squash in Illinois is just the beginning.
Here’s how to keep your plants thriving all season.
1. Water Consistently
Squash needs about 1 inch of water per week.
Water deeply at the base of the plant to avoid wetting the leaves, which can lead to powdery mildew.
2. Watch for Pests
Squash bugs and vine borers are common problems in Illinois.
Check under leaves regularly and use row covers early in the season to protect young plants.
3. Fertilize Wisely
Side-dress your squash with compost or a balanced fertilizer once flowers appear.
Don’t overdo nitrogen, or you’ll get lots of leaves and few fruits.
4. Harvest at the Right Time
Summer squash is ready 50 to 60 days after planting squash in Illinois.
Pick them when they’re 6 to 8 inches long for the best flavor.
Winter squash takes 80 to 100 days and is ready when the skin is hard and can’t be punctured with a fingernail.
So, When to Plant Squash in Illinois?
The best time to plant squash in Illinois is from late May to early June, after the last frost and once the soil has warmed to at least 60°F.
Summer squash can go in through early July, while winter squash should be planted by early June for a full harvest.
If you follow these guidelines for when to plant squash in Illinois, you’ll be rewarded with a bountiful crop.
Happy gardening!