When to Plant Watermelon in St. George, UT
Published: April 24, 2026
Watermelon Planting Dates for St. George, UT
| Start seeds indoors | March 1–8 |
| Last frost (average) | March 22 |
| Transplant outdoors | April 5–15 |
| Direct sow outdoors | April 5–15 |
| Minimum soil temperature | 65°F |
| Expect first harvest | June 14 – July 4 |
| First fall frost (average) | November 10 |
⚠ Plant watermelon 2 weeks after last frost when soil exceeds 65°F. Needs 70–90 frost-free days. Direct sow in warm climates; start indoors in Zone 4–5.
Best Watermelon Varieties for St. George, UT
Consult a St. George-area nursery or your state extension office for watermelon varieties proven in Zone 6b.
Growing Watermelon in St. George
St. George sits in Zone 6b, with an average last frost of March 22 and first fall frost around November 10 — giving a 233-day frost-free growing season. Warm-season crops like watermelon need soil at 65°F or above before transplanting; St. George's frost calendar puts that window clearly in the late-spring to early-fall range.
St. George's moderate climate supports watermelon on the standard transplant calendar with minimal special accommodation. Succession planting — sowing fresh seeds or setting new transplants every 2–3 weeks through spring — stretches the harvest window and gives you a backup crop if pests hit the first planting.
St. George's caliche soil is rock-hard below the surface — raised beds filled with quality potting mix are the most practical approach for watermelon. Breaking through caliche for in-ground planting requires significant soil amendment, gypsum application, and deep tilling over several seasons. Water at 2 inches per week delivered through drip irrigation for best results in a raised-bed system.
Watermelon Calendar for St. George
| Month | Task |
|---|---|
| March | Start seeds indoors under grow lights |
| April | Transplant outdoors into warm soil |
| June | Expect first harvest window to open |
| November | First fall frost — harvest remaining, end of outdoor season |
Watermelon Tips for St. George Gardeners
- •Plant on a warm, sunny slope or use black plastic mulch to maintain soil temperature above 70°F all season.
- •Give each plant 6 feet of space — watermelon vines sprawl and need room to run.
- •Succession plant watermelon in St. George every 2–3 weeks through spring to extend the harvest window into summer.
Common Watermelon Pests in St. George
- •Cucumber Beetle — peaks July in Zone 6b (active May–September); yellow and black striped beetles that spread bacterial wilt; trap with yellow sticky traps.
- •Squash Bug — peaks July in Zone 6b (active May–September); gray-brown shield bugs that suck plant sap; handpick and destroy egg clusters on leaf undersides.
- •Aphids — peaks July in Zone 6b (active May–September); clusters on leaf undersides; blast with a strong water spray or apply neem oil.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Watermelon in St. George
In St. George's moderate climate, Corn and Radish are the most beneficial plants to grow alongside watermelon. Corn provides vertical support for climbing companions in the Three Sisters planting. Keep watermelon away from Cucumber — it competes for nutrients or shares pest pressure.
Frequently Asked Questions
When should I plant watermelon in St. George, UT?
In St. George (Zone 6b), start watermelon seeds indoors around March 1–8 and transplant outdoors around April 5–15. The city's average last frost of March 22 is the anchor date — count 3 weeks back for seed starting and 2 weeks forward for transplanting.
What zone is St. George, UT for watermelon growing?
St. George is USDA Zone 6b. For watermelon, this means a frost-free growing season of roughly 33 weeks running from March 22 to November 10. This is a comfortable window for warm-season crops like watermelon — standard varieties work well.
When is watermelon harvest season in St. George?
Expect the first watermelon harvest in St. George around June 14, with harvest continuing through July 4. This is based on 70–90 days from transplant or direct sow.
How long does it take to grow watermelon in St. George, UT?
From transplant or direct sow to first harvest, watermelon takes 70–90 days in St. George's climate. Based on a typical planting date of April 5–15, expect your first harvest around June 14. St. George's Zone 6b transition-zone climate produces maturity times right in the middle of the stated range.
What soil does watermelon need in St. George?
St. George's caliche subsoil is effectively rock — traditional in-ground planting of watermelon produces poor results. Build a raised bed with 12–18 inches of quality potting mix or Mel's Mix for reliable production. Break through caliche only for deep-rooted crops, and expect to add compost each year to offset the alkalinity.