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- Fall crop
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Historical frost averages plus extension guidance, not a forecast. Check the forecast and soil temperature before planting.
Sow sweet corn outside 1–3 weeks after your last spring frost, once the soil is at least 50°F; 60°F or warmer is better, and supersweet types need 65°F. Plant in blocks of at least four short rows rather than one long row so the ears fill out well.
- Frost tolerance
- Tender: no frost
- Soil temperature
- Sow at 50°F+, best 60–95°F
- Days to harvest
- 60–90 days, by variety
The rule we use
- Sow outdoors: 1–3 weeks after the last spring frost
Plant in blocks, not rows
Corn is pollinated by the wind. Pollen falls from the tassels at the top onto the silks below, and each silk that catches pollen makes one kernel. A single long row lets most pollen blow away, leaving ears with gaps.
Plant at least four rows side by side, 30–36 inches apart, with seeds 1–2 inches deep and 8–12 inches apart in the row.
Soil warmth and variety types
Cold, wet soil rots corn seed. Standard sugary types sprout at 50°F. Sugar-enhanced types like a little warmer, and supersweet types need about 65°F because their seeds have less stored energy.
Keep supersweet corn at least 250 feet from other types, or time it to tassel at a different time. If they cross, both can turn starchy.
Spreading out the harvest
Each planting is ready over about a week. For corn all summer, sow a new block every 2 weeks, or plant early, mid and late varieties on the same day.
In short-season areas, choose early varieties of 60–70 days. Check the ears about 3 weeks after the silks appear: the silks should be brown and dry, and a kernel pressed with a fingernail should squirt milky juice.
Seeds and supplies for sweet corn
- Sweet corn seeds at True Leaf Market
- Park Seed for seeds and young plants.
- A soil thermometer to check the soil is warm enough before sowing.
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Questions about planting sweet corn
When should I plant sweet corn?
About 1–3 weeks after your last frost, when soil is at least 50–60°F. Enter your ZIP above for dates.
Why are my corn ears missing kernels?
Usually poor pollination. Plant in a block of four or more rows, not a single row.
How late can I plant sweet corn?
Until about 12–14 weeks before your first fall frost for most varieties. Check your variety's days to maturity.
Sources
- Vegetable Planting Calendar for Central Maryland (2026), University of Maryland Extension
- Vegetables for Spring and Fall Planting; Vegetables for Summer Planting, University of Maryland Extension Master Gardeners
- Suggested Vegetable Planting Dates for Utah, Utah State University Extension
- Vegetable Planting Guide (CMG GardenNotes #720), Colorado State University Extension
- Soil temperature conditions for vegetable seed germination, Oregon State University Extension
- Extension Gardener Handbook, Ch. 16: Vegetable Gardening, NC State Extension
- Frost dates: NOAA NCEI U.S. Climate Normals 1991–2020 (doi:10.25921/4ek7-fk11)