Sweet corn is sown directly in the garden one to two weeks after your last spring frost, once the soil has warmed. Find your zone below, or enter your ZIP code for dates based on the weather station closest to you.
Sweet corn dates for your ZIP code
Planting times based on university extension guidance (UNH, Cornell, Purdue, Minnesota, Nebraska and UMass Extension). Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Sweet corn planting dates by zone
| USDA zone | When to plant |
|---|---|
| Zone 3 | May 30 – June 6 |
| Zone 4 | May 23 – May 30 |
| Zone 5 | May 15 – May 22 |
| Zone 6 | May 8 – May 15 |
| Zone 7 | April 24 – May 1 |
| Zone 8 | April 7 – April 14 |
| Zone 9 | March 10 – March 17 |
Not sure of your zone? Look it up by ZIP code.
Why sweet corn waits for warm soil
Sweet corn is a warm-season crop. Frost damages it, and its seed rots in cold, wet soil. It germinates best at soil temperatures of 60–85 °F and needs at least 50 °F, or 65 °F for supersweet varieties. That is why it is sown one to two weeks after the last spring frost.
How to plant sweet corn
- Sow directly in the garden, about 1 inch deep in early plantings and 1–2 inches later in the season.
- Space seeds 8–10 inches apart in rows 2½–3 feet apart.
- Plant in a block of at least three or four short rows for good pollination.
- Fertilize before planting, then side-dress with nitrogen when plants are 15–18 inches tall.
- Water about an inch a week, especially in the two weeks before silks appear.
Harvesting sweet corn
Sweet corn is ready about 20 days after the first silks appear, when the silks are dry and brown, the husks are still green and the ears feel plump. Pull back a husk to check: the kernels should be full and milky. Pick in the cool of early morning and refrigerate right away, because the sugar turns to starch quickly in warm temperatures.
Frequently asked questions
What do su, se and sh2 mean on sweet corn seed?
They are sweetness types. Standard (su) is the classic flavor, sugar-enhanced (se) is sweeter and holds its sugar longer, and supersweet (sh2) is the sweetest but needs warm soil and must be kept apart from other corn.
Why plant sweet corn in blocks?
Corn is pollinated by wind, and each kernel needs its own grain of pollen. A block of several short rows catches pollen much better than a single long row.
How long does sweet corn take to grow?
About 80–100 days from sowing, depending on the variety.
Sources. Planting dates use the median frost dates of each USDA zone, calculated from NOAA climate data for every ZIP code in the zone.