When to Plant Tomatoes in St. Louis, MO
Published: April 21, 2026
Tomato Planting Dates for St. Louis, MO
| Start seeds indoors | February 8–15 |
| Last frost (average) | March 22 |
| Transplant outdoors | April 5–15 |
| Minimum soil temperature | 60°F |
| Expect first harvest | June 4 – June 29 |
| Fall crop planting | August 18–28 |
| Fall crop harvest | October 17 |
| First fall frost (average) | November 10 |
⚠ Warm-climate gardeners (TX, FL, AZ) can grow TWO crops: spring (Feb–March transplant) and fall (July transplant for October harvest).
Best Tomato Varieties for St. Louis, MO
For Zone 6b St. Louis, the best-performing tomato varieties are Big Beef, Early Girl, and Better Boy — all widely adapted, disease-resistant varieties proven across the transition zone. Cherokee Purple is a good alternative where disease resistance matters most, especially in humid summers. These varieties are typically stocked by local nurseries and are the safest bets for gardeners new to tomato in St. Louis.
Growing Tomatoes in St. Louis
St. Louis 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 tomato need soil at 60°F or above before transplanting; St. Louis's frost calendar puts that window clearly in the late-spring to early-fall range.
St. Louis's moderate climate supports tomato 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. Louis's clay-loam soils are productive but benefit from annual compost amendment — 2 to 3 inches worked in before planting improves drainage and nutrient availability for tomato. Consistent watering (1.5 inches per week) paired with organic mulch maintains the even moisture that clay-loam holds well. Avoid working wet soil in spring, which causes severe compaction in clay-loam blends.
Tomato Calendar for St. Louis
| Month | Task |
|---|---|
| February | Start seeds indoors under grow lights |
| March | Last frost — harden off seedlings outdoors |
| April | Transplant outdoors into warm soil |
| June | Expect first harvest window to open |
| August | Start fall crop — transplants or direct sow |
| November | First fall frost — harvest remaining, end of outdoor season |
Tomato Tips for St. Louis Gardeners
- •Bury the stem 2/3 deep when transplanting — roots grow from the buried stem for a stronger plant.
- •Consistent watering prevents blossom end rot and fruit cracking; uneven moisture causes both.
- •Succession plant tomato in St. Louis every 2–3 weeks through spring to extend the harvest window into summer.
Common Tomato Pests in St. Louis
- •Tomato Hornworm — peaks July in Zone 6b (active May–September); look for 3–4 inch green caterpillars with white stripes; handpick into soapy water or apply Bt spray.
- •Aphids — peaks July in Zone 6b (active May–September); clusters on leaf undersides; blast with a strong water spray or apply neem oil.
- •Early Blight — peaks July in Zone 6b (active May–September); dark rings on lower leaves; remove affected leaves and apply copper fungicide.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Tomatoes in St. Louis
In St. Louis's moderate climate, Basil and Marigold are the most beneficial plants to grow alongside tomato. Basil repels whiteflies, aphids, and spider mites, and is planted at the same time as its partners. Keep tomato away from Potato — it competes for nutrients and shares blight diseases.
Frequently Asked Questions
When should I plant tomato in St. Louis, MO?
In St. Louis (Zone 6b), start tomato seeds indoors around February 8–15 and transplant outdoors around April 5–15. The city's average last frost of March 22 is the anchor date — count 6 weeks back for seed starting and 2 weeks forward for transplanting.
What zone is St. Louis, MO for tomato growing?
St. Louis is USDA Zone 6b. For tomato, 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 tomato — standard varieties work well.
When is tomato harvest season in St. Louis?
Expect the first tomato harvest in St. Louis around June 4, with harvest continuing through June 29. This is based on 60–85 days from transplant or direct sow. A fall crop planted August 18–28 adds a second harvest around October 17.
How long does it take to grow tomato in St. Louis, MO?
From transplant or direct sow to first harvest, tomato takes 60–85 days in St. Louis's climate. Based on a typical planting date of April 5–15, expect your first harvest around June 4. St. Louis's Zone 6b transition-zone climate produces maturity times right in the middle of the stated range.
What soil does tomato need in St. Louis?
St. Louis's clay-loam soil is productive for tomato but benefits from annual compost amendment. Work 2–3 inches of compost into the top 10 inches before planting. Avoid working wet soil in spring — clay-loam compacts badly when wet. Consistent watering paired with organic mulch maintains the even moisture these soils hold well.