Spring Planting Tips

Now that your garden is planned and prepped, it’s time for the most exciting step—PLANTING! 🌱 But before you start digging, understanding frost dates, soil temperatures, and which plants thrive in cool vs. warm weather will help ensure a strong, healthy start to the season.

At Thomas Greenhouse & Garden Center in Mukwonago, WI, we love helping gardeners choose the right plants at the right time so they can enjoy a thriving garden all season long. Whether you’re planting from seed or transplanting starter plants, this guide will help you make the best choices for your space!

 

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🌡 Understanding Frost Dates & Soil Temperature: When Is It Safe to Plant?

Wisconsin weather can be tricky in spring. Even when we get beautiful 60- or 70-degree days, nighttime temperatures can still drop near freezing. ❄️

✅ Southeastern Wisconsin’s average last frost date: May 10–20
✅ Soil temperature matters just as much as air temperature!

 

• • Cool-season crops can handle soil temps as low as 40°F.
  • Warm-season plants need soil temps of 55–65°F for best results.

 

💡 Pro Tip: Invest in a soil thermometer to check if your garden is ready! Insert it 2–4 inches into the soil and take readings in the morning for the most accurate results. If the soil is too cold, seeds won’t germinate, and transplants may struggle to establish.

🚨 Don’t plant too early! Young plants, seeds, and seedlings are fragile and can freeze—and when they do, there’s little hope for recovery. If you’re unsure whether it’s time to plant, ask us at Thomas Greenhouse—we’ll help you decide!

 

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🛑 Stop Here! Unlock the Full Guide for Expert Planting Tips!

🌱 Ready to plant a thriving spring garden? You’ve learned when it’s safe to plant—now get expert guidance on:
✅ What to plant and when (Cool-season vs. warm-season crops)
✅ Best methods for planting seeds vs. starter plants
✅ How to give your plants the healthiest start

🔓 Unlock the full guide now! Sign up below to access detailed planting timelines, transplanting tips, and expert advice from Thomas Greenhouse & Garden Center!

 

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🌱 Cool-Season vs. Warm-Season Planting

Knowing what to plant and when is key to a successful garden. Some plants love cool spring temps, while others need consistent warmth before they thrive.

 

🥕 Cool-Season Plants (Plant as soon as the soil is workable – 40°F and up)

These frost-hardy vegetables and flowers can handle cooler weather and should be planted early to take advantage of spring’s mild temps.

 

✅ Vegetables & Herbs:

 

• • Lettuce 🥬
  • Spinach
  • Kale
  • Peas
  • Radishes
  • Carrots
  • Broccoli 🥦
  • Cauliflower
  • Brussels sprouts
  • Cilantro
  • Parsley

 

 

✅ Flowers:

 

• • Pansies 🌸 (Can handle light frost!)
  • Violas
  • Snapdragons
  • Dianthus

 

🌟 Extra Tip: Keep an eye on the forecast! If a hard freeze (below 28°F) is predicted, cover young plants with frost cloth, overturned pots, or even an old sheet overnight.

 

🍅 Warm-Season Plants (Plant AFTER the last frost – when nights are consistently above 50°F and soil is 55°F+)

These plants cannot tolerate frost and need warm soil and air temperatures to grow strong.

 

✅ Vegetables & Herbs:

 

• • Tomatoes 🍅
  • Peppers
  • Cucumbers 🥒
  • Squash
  • Zucchini
  • Beans
  • Corn 🌽
  • Basil
  • Dill

 

 

✅ Flowers:

 

• • Petunias
  • Marigolds
  • Zinnias
  • Dahlias
  • Sunflowers 🌻

 

🚨 Warning: Don’t rush planting warm-season crops! Even one cold night can stunt growth or kill fragile plants.

🌟 Pro Tip: If you’re eager to get started, use row covers or cloches to keep young transplants warm on cool nights.

 

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🌿 Direct Sowing vs. Transplants: Which Works Best?

Some plants thrive when directly sown into the soil, while others do better as transplants. Understanding the difference will save you time, money, and frustration!

 

🌱 Best Plants for Direct Sowing (Plant seeds straight into the garden)

 

• • Carrots 🥕
  • Radishes
  • Lettuce
  • Spinach
  • Beans
  • Peas
  • Sunflowers 🌻
  • Corn 🌽

 

🌟 Extra Tip: For successful germination, keep soil consistently moist until seedlings are well established.

 

🌿 When to Buy Starter Plants from Thomas Greenhouse

While growing from seed is great for some plants, there are many reasons why buying starter plants (transplants) can be the better choice.

 

✅ Best to Buy as Starter Plants:

 

• • Tomatoes, Peppers, & Eggplants – Need a long season and warm temps
  • Broccoli, Cauliflower, & Brussels Sprouts – Stronger when started early
  • Cabbage & Celery – Require a head start for the best results
  • Basil, Rosemary, & Lavender – Slow to grow from seed
  • Petunias, Marigolds, & Snapdragons – Bloom sooner as transplants

 

 

🌟 Extra Tip: When transplanting, harden off your plants first! Gradually expose them to outdoor conditions over 5–7 days before planting to prevent shock.

💡 Not sure what to plant? Stop by Thomas Greenhouse, and we’ll help you pick the best starter plants for your garden!

 

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❌ Common Wisconsin Planting Mistakes to Avoid!

🚫 Planting too early – Late frosts can kill tender plants. Always check soil temperature!
🚫 Skipping hardening off – Sudden outdoor exposure can shock young transplants.
🚫 Overwatering seedlings – Too much moisture can cause root rot or fungal diseases.

 

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🌸 Ready to Start Planting? We’re Here to Help!

At Thomas Greenhouse & Garden Center in Mukwonago, WI—near Waukesha and Lake Geneva—we have:
✅ High-quality vegetable and flower starter plants
✅ A wide selection of herbs ready to go in the ground
✅ Locally grown, hardy transplants that thrive in Wisconsin
✅ Expert advice to help you choose the best plants for your garden!

 

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🌱 Next in the Series: Early Season Garden Care!

Now that your plants are in the ground, what’s next? Stay tuned for tips on watering, feeding, and protecting young plants so they thrive all season long!

🌱 We can’t wait to see you this spring! Stop by soon! 😊