🌽When to Plant Corn in USDA Zone 6a (2026 Guide)
Sow directly in warm soil. Plant in blocks for good pollination. Here is the warm-season planting schedule for corn in zone 6a (covering areas like St. Louis MO, Philadelphia PA). All dates are based on 2026 frost data for your zone.
Direct sow
May 4
Harvest From
Jul 23
Because corn is a warm-season crop that frost will kill, wait until about May 4 in zone 6a — safely after the average last frost on Apr 20.
- Type: Warm-season
- Method: Direct sow
- Days to harvest: 80
- Spacing: 12" apart
- Sun: Full sun
- Zone 6a frost: Apr 20 – Oct 15
- Season length: ~178 days
- Companions: beans, squash, cucumber
Growing corn in zone 6a
Zone 6a has an average last spring frost around Apr 20 and a first fall frost around Oct 15, giving roughly 178 frost-free growing days. That window comfortably fits corn's 80-day cycle, with room for a second succession planting if you time it right.
Corn resents transplanting, so direct sow it right in the garden around May 4. Give each plant about 12 inches of space in full sun.
Zone 6a specific growing notes
In zone 6a (St. Louis MO, Philadelphia PA), your 178-day growing season means corn should be planted only after the soil has thoroughly warmed. Warm-season crops like corn need soil temperatures of at least 60°F. In zone 6a's climate, using black plastic mulch can warm the soil 2-3 weeks earlier.
Your first fall frost around Oct 15 means your last possible harvest is roughly late Oct. For a continuous supply, consider succession planting every 2-3 weeks from May 4 through mid-season.
Pro tip for corn
Plant in blocks of at least 4 short rows, not one long single row. Corn is wind-pollinated—each silk must receive pollen from a neighboring tassel. Poorly pollinated ears have missing kernels.
Troubleshooting corn
Corn earworms enter through the silk tips and feed on developing kernels. Apply a few drops of mineral oil or Bt mixed with oil to the silk tips 5-7 days after silks first appear.
Growing corn in containers
Possible in large containers (20+ gallons) with at least 9-12 stalks planted closely for wind pollination. Choose shorter varieties like 'Trinity' or 'On Deck' bred for containers. Expect 1-2 ears per stalk.
Can you plant corn twice a year?
Yes in zones 6+—sow a second block 3 weeks after the first for staggered harvest. In zones 7+, you can fit three successions. Choose varieties with different maturity dates for a longer harvest window.
Frequently asked questions
When should I plant corn in zone 6a?
Direct sow around May 4. Because corn is a warm-season crop that frost will kill, wait until about May 4 in zone 6a — safely after the average last frost on Apr 20.
How long does corn take to grow in zone 6a?
About 80 days from sowing to first harvest. A May 4 planting in zone 6a is typically ready to pick from around Jul 23. Zone 6a has about 178 frost-free days — plenty of time for a second succession planting.
How far apart should I space corn?
Space corn about 12 inches apart in full sun. This gives each plant enough room for roots to spread and leaves to catch sunlight without competing.
What is the best tip for growing corn?
Plant in blocks of at least 4 short rows, not one long single row. Corn is wind-pollinated—each silk must receive pollen from a neighboring tassel. Poorly pollinated ears have missing kernels.
What are common problems with corn and how do I fix them?
Corn earworms enter through the silk tips and feed on developing kernels. Apply a few drops of mineral oil or Bt mixed with oil to the silk tips 5-7 days after silks first appear.
Can I grow corn in a container?
Possible in large containers (20+ gallons) with at least 9-12 stalks planted closely for wind pollination. Choose shorter varieties like 'Trinity' or 'On Deck' bred for containers. Expect 1-2 ears per stalk.
Can I plant a second crop of corn for fall harvest?
Yes in zones 6+—sow a second block 3 weeks after the first for staggered harvest. In zones 7+, you can fit three successions. Choose varieties with different maturity dates for a longer harvest window.
What grows well next to corn?
Good companion plants for corn are beans, squash, cucumber. Avoid planting near cool-season crops that have different watering needs. Corn also benefits from crop rotation — do not plant it in the same spot year after year.