When to Plant Potatoes in St. Louis, MO
Published: April 24, 2026
Potato Planting Dates for St. Louis, MO
| Start seeds indoors | Year-round |
| Last frost (average) | March 22 |
| Direct sow outdoors | March 1–11 |
| Minimum soil temperature | 45°F |
| Expect first harvest | May 10 – June 29 |
| First fall frost (average) | November 10 |
⚠ Plant seed potatoes 2–4 weeks before last frost when soil is workable and above 45°F. Hill soil up around stems as plants grow. Needs well-drained, loose soil.
Best Potato Varieties for St. Louis, MO
Consult a St. Louis-area nursery or your state extension office for potato varieties proven in Zone 6b.
Growing Potatoes 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. Cool-season crops like potato benefit from St. Louis's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
St. Louis's moderate climate supports potato 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 potato. 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.
Potato Calendar for St. Louis
| Month | Task |
|---|---|
| Year | Start seeds indoors under grow lights |
| March | Direct sow seeds into warm soil |
| May | Expect first harvest window to open |
| November | First fall frost — harvest remaining, end of outdoor season |
Potato Tips for St. Louis Gardeners
- •Cut seed potatoes into 2-inch chunks with at least two eyes each, then let cut surfaces heal for 24–48 hours before planting.
- •Plant 4 inches deep and 12 inches apart in loose, well-drained soil; add compost but avoid fresh manure.
- •Succession plant potato in St. Louis every 2–3 weeks through spring to extend the harvest window into summer.
Common Potato Pests in St. Louis
- •Colorado Potato Beetle — peaks July in Zone 6b (active May–September); monitor closely during peak season and treat early.
- •Wireworm — peaks July in Zone 6b (active May–September); orange-brown beetle larvae in soil; trap with cut potato pieces buried in soil.
- •Potato Scab — peaks July in Zone 6b (active May–September); monitor closely during peak season and treat early.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Potatoes in St. Louis
In St. Louis's moderate climate, Bean and Corn are the most beneficial plants to grow alongside potato. Bean improves nearby plant health and pest resistance. Keep potato away from Tomato — it competes for nutrients or shares pest pressure.
Frequently Asked Questions
When should I plant potato in St. Louis, MO?
In St. Louis (Zone 6b), direct sow potato around March 1–11. Soil must be at 45°F or warmer at 2-inch depth before sowing — cold soil rots the seeds.
What zone is St. Louis, MO for potato growing?
St. Louis is USDA Zone 6b. For potato, this means a frost-free growing season of roughly 33 weeks running from March 22 to November 10. Cool-season crops like potato thrive in this zone with both spring and fall planting windows available.
When is potato harvest season in St. Louis?
Expect the first potato harvest in St. Louis around May 10, with harvest continuing through June 29. This is based on 70–120 days from transplant or direct sow.
How long does it take to grow potato in St. Louis, MO?
From transplant or direct sow to first harvest, potato takes 70–120 days in St. Louis's climate. Based on a typical planting date of March 1–11, expect your first harvest around May 10. St. Louis's Zone 6b transition-zone climate produces maturity times right in the middle of the stated range.
What soil does potato need in St. Louis?
St. Louis's clay-loam soil is productive for potato 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.