How to grow sweet corn
Family Poaceae. Hardy to USDA hardiness zone 4a+ (U.S. Department of Agriculture). Full sun. Ready in 65-90 days.
Sun
Full sun
Spacing
12 in (block plant)
Days to harvest
65-90 days
Hardiness
Zone 4a+
What growers actually recorded
Loading zone 7b results…
When to plant sweet corn
- Direct sow: ~2 weeks after last frost.
Companion plants for sweet corn
Plant with: Bean, Squash, Cucumber.
Avoid near: Tomato.
Common pests & problems
Corn earworm. A drop of mineral oil on the silks after pollination helps.
Feeding & fertilizer
N-P-K ratio: High N (10-5-5): corn is a nitrogen hog
Organic options: Compost + aged manure deep in the row · Blood meal side-dress at knee-high · Fish emulsion at tasseling
When to feed: Feed at planting, knee-high, and tasseling: three big meals.
Watch for: Small ears / missing kernels = under-feeding or poor pollination.
N = nitrogen (leaves), P = phosphorus (roots and flowers), K = potassium (fruit and disease resistance). How to read a fertilizer label →
Grower's tip
Plant in a block at least 4×4 for wind pollination, not a long row.
When to plant sweet corn in your zone
Free month-by-month sowing and transplanting lists, built from frost dates for your USDA (United States Department of Agriculture) hardiness zone.
Soil & water for sweet corn
Soil & pH
6.0-6.8
Deep, fertile, well-drained. Corn is a nitrogen hog and shallow rooter for its size.
Compost + aged manure worked deep. Side-dress blood meal at knee-high; again at tasseling.
Watering
1-1.5 in / week; 2 in during silking
Drip or furrow. Water stress during silking = missing kernels.
Corn is shallow-rooted and loud about it. If leaves are still rolled by 10 AM after the dew has burned off, water that day. Don't wait for the whole row to droop.
Knowing when to harvest
- Silks brown and dry, ear feels full to the tip.
- Puncture a kernel. Clear liquid = too early; milky = perfect; doughy = too late.
- Pick and eat within 24 hours (sugar-enhanced varieties buy you a few days).
Storing & keeping
Refrigerate immediately, use within 3-5 days. Blanch and freeze cut kernels for 12 months.
What to expect
Per plant: 1-2 ears
Per sq ft: 1 ear / sq ft in block plantings
Troubleshooting sweet corn
Missing kernels on the ear
Likely cause: Poor pollination. Row too small or water-stressed
What to do: Plant in a block at least 4×4, hand-shake tassels at midday.
Worm in the tip
Likely cause: Corn earworm
What to do: Drop of mineral oil on silks 5 days after silking; open eartip and remove.
Varieties worth growing
Silver Queen (white)
Classic sweet, disease-resistant, late-season.
Bodacious (yellow)
Sugar-enhanced (SE); holds sweetness longer.
Painted Mountain (flour)
Cold-tolerant heirloom, grinds for polenta.
Growing sweet corn in containers
Not recommended: pollination fails without a block.
Nutrition
Complex carbohydrate, fiber, folate; pair with beans for complete protein.
Common questions
Why do I need to plant corn in a block?
Corn is wind-pollinated. A long row means pollen misses most silks. A 4×4 minimum grid ensures full kernels.
Where these numbers come from
- USDA Plant Hardiness Zone Map (2023 revision). Zone assignment and the 30-year normals behind every cold-hardiness figure.
- NOAA NCEI 1991-2020 Climate Normals. Frost dates, growing-season length, and the probability bands on both.
- Cornell, UMN, and UC Davis Cooperative Extension crop guides. Spacing, days to maturity, soil pH targets, and per-plant yield ranges.
- USDA FSIS / FDA Produce Safety guidance. Wash, cure, and cold-storage handling numbers.
Ranges are regional guidance, not a promise for your yard. Your own logged results always override the published range.