Sweet corn in Arkansas is ready 60 to 90 days after planting, and the ear stays at its best for only a short stretch. Pick when three signs agree: dry brown silks, husks still moist and green, and milky juice from a punctured kernel. Once the ear is off the stalk, sugar starts leaving the kernel, and heat speeds that up. The planting date and the seed type decide when those few good days arrive. For the full growing picture, see Growing Sweet Corn in Arkansas.
The short answer
Soil reaches 60 F later than the last frost, and that gap sets the whole calendar. At the Little Rock reference station, NOAA NCEI Climate Normals put the last spring 32 F freeze between March 12 and March 28 (the 30-70% probability band). The air passes that line well before the ground does. Utah State University Extension asks for soil above 60 F, so the soil thermometer tells you when to sow, not the frost date.
Depth matters. Clemson Extension says: “Do not plant before the soil temperature at the 4-inch depth is at least 50 ºF. Wait to plant extra-sweet varieties until soil temperatures reach 65 °F.” The two numbers are not interchangeable. Fifty degrees is the floor for ordinary sweet corn, and extra-sweet (sh2) seed sown that cold rots instead of sprouting. That is why a gardener can do fine one year and fail the next after switching seed. A surface reading runs warmer than the soil 4 inches down, so push the thermometer in. Soil temperature is the instruction here, and no calendar date can replace it.
The other end of the season is roomy. The first fall 32 F freeze at the same station falls between November 7 and November 20. From the late edge of the spring window to the early edge of the fall one is 224 days, so a crop that needs 60 to 90 days fits, even after you wait for warm soil. Heat is the other half of the picture: the reference station averages 69.2 days a year at 90 F or more, nearly ten weeks’ worth. Most Arkansas corn finishes inside that heat.
Two clocks, two questions
Two separate counts run here. The 60 to 90 days from planting tells you whether a variety fits the season. A second count, 17 to 24 days from the moment silks first emerge, tells you which week to pick. Keep them apart. When the second window opens, check three signs together: the silks have dried and gone brown, the husks are still moist and green, and a punctured kernel gives milky juice. Any one alone can mislead you.
How fast it fades
Clemson Cooperative Extension (HGIC factsheet on sweet corn) puts it this way: “Sweet corn loses sugar from the kernel rapidly at high temperatures… Sweet corn can be stored under optimal conditions for about five days, but will lose sweetness with each day of storage.” About five days is a ceiling under ideal conditions, not a promise, and a July kitchen counter in Arkansas is not ideal. This is the mechanism behind the old advice to run from the garden to the pot. Genotype changes the pace: su loses sugar fastest, se holds it longer, and sh2 holds it longest. For a gardener who can’t eat the harvest the same day, that is the practical reason to choose one type over another.
Does a late variety fit here?
Both ends of the range fit. What differs is how much room each one leaves before the first fall freeze, and how much of its life it spends in the hottest weeks. The exact sowing weeks are laid out in When to Sow Sweet Corn in Arkansas. Here the question is only whether the arithmetic holds.
A 60-day variety
Sixty days is a little over a quarter of the 224 days between the late edge of the last-frost window and the early edge of the first-freeze window. Even if you wait for soil to reach the temperature your seed type needs, the margin is measured in months. That margin leaves room for a second sowing after the first is up, as long as both plantings are the same type. Mixed types are where trouble starts, and the next section covers it.
The fast type has one more advantage in this climate. A short crop spends fewer days exposed to a summer that brings 90 F or more on 69.2 days in an average year. The ears still need steady water, but the clock runs out sooner.
A 90-day one
It fits, with a limit. Counting back 90 days from November 7, the early edge of the first-freeze window, lands in early August. A 90-day type sown later than that does not fit, because it would be racing a freeze that can arrive on the early side of the window. And the window is a probability band, not a promise, so a sensible gardener sows well before that line rather than on it.
For a spring sowing made once the soil is warm, the 90-day type has plenty of room. It will ripen deep in the hot season, though, and that raises water demand. It also puts more pressure on the days after picking, since sugar drains faster the hotter the ear stays. If you grow the late type, plan to cool and eat the ears quickly.
What goes wrong here
Most failures in this climate come from one of three causes. The third has nothing to do with weather.
- Seed sown into cold soil. The last frost has passed, the afternoon feels warm, and the seed goes in. It sits and rots, most often with extra-sweet types. The remedy is a thermometer at 4 inches: at least 50 F for ordinary sweet corn, 65 F for extra-sweet. Treating the frost date as the planting date is the common mistake, because soil warms well after the air does.
- A variety too late for the season. Arkansas has a long season, so this failure shows up when sowing slips, not when spring is slow. Add the variety’s days to maturity to your sowing date and check that the result lands before the first-freeze window of November 7 to November 20, with room to spare. If it doesn’t, switch to a shorter type or sow sooner.
- Sweetness lost to the neighbor. Sweetness is decided by what tassels nearby. When su, se and sh2 types tassel at the same time, the sweetness is lost. The source gives no separation distance, so the advice rests on timing. Sow the types at different times so their tassels don’t overlap, or grow a single type. Plant in blocks of three or more rows rather than one long row.
Insects and animals cause a different set of losses, with their own calendar. What Eats Corn in Arkansas, and When covers them.
Common questions
How do I know an ear is ready to pick?
Use three signs together: dry brown silks, husks that are still moist and green, and milky juice when you puncture a kernel. As a guide to timing, the harvest window falls 17 to 24 days after silks first emerge. That count is separate from the 60 to 90 days from planting.
Can I plant as soon as the last frost has passed?
No. The last 32 F freeze at the Little Rock reference station falls between March 12 and March 28, but soil reaches 60 F later. Clemson Extension asks for at least 50 F at the 4-inch depth for ordinary sweet corn and 65 F for extra-sweet types.
How long do picked ears keep their sweetness?
Clemson says about five days under optimal conditions, and that is a maximum. Sweetness drops with each day of storage, and heat speeds the loss. The su type loses sugar fastest, se holds it longer, and sh2 longest.
Can I grow su, se and sh2 types in the same garden?
Yes, as long as they don’t tassel at the same time. Separate the plantings by timing, and grow each in a block of three or more rows. The university source behind this page publishes no separation distance, so none is given here.