An ear of sweet corn is ready when the silks have dried brown, the husk is still moist and green, and a punctured kernel gives milky juice. All three signs need to show up together. In Nunavut the calendar is far less certain than the plant, and once an ear is picked the sugar starts leaving the kernel, faster in warmth than in cold. Both halves of the answer are below.
When sweet corn are ready in Nunavut
Look for dry brown silks, a husk that is still moist and green, and milky juice when you press a thumbnail into a kernel. If you want a window, plan on late August at the very earliest and more likely September, in a year when the corn fits the season at all. The signal travels from garden to garden. The date does not.
How long is the growing season at Rankin Inlet A?
The reference station, Rankin Inlet A, has about 86 frost-free days between the mean last spring frost of June 19 and the mean first fall frost of September 13. Both come from Environment and Climate Change Canada’s climate normals. They are midpoints. In one year out of two the last spring frost falls later than June 19, and in one year out of two the first fall frost arrives earlier than September 13. Northern and inland districts of Nunavut can run weeks behind this station, so treat the dates as the middle of a window.
When is the soil warm enough, and does the season leave room?
Soil at planting depth warms well after the last frost, and that matters more than the frost date. Clemson Cooperative 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 thresholds are not interchangeable. Ordinary sweet corn can go in at the lower one. Extra-sweet types sown into 50 F soil tend to rot rather than sprout. Utah State University Extension adds that sweet corn needs soil above 60 F and 60 to 90 days from planting.
Put those together. A seed sown on the mean last frost date, which the soil will not allow in most years, would need until mid-to-late August on the short end of that range. On the long end it would run past mid-September. Every week the soil takes to warm comes off the back of the season. Only the fastest-maturing seed has a chance, and a short-season type is the first thing to look for on the packet. When to Sow Sweet Corn in Nunavut covers the sowing side in detail.
How do you pick the right week?
The 60 to 90 days run from planting and tell you whether the crop fits the season. A second clock tells you which week to pick. Ears are usually ready a few weeks after the first silks appear. Mark the day you first see silks, then start checking the ears around the early end of that range. Squeeze the husk, peel back a strip, and run the three-sign test.
What else decides whether the ears are sweet?
Sweetness depends on what tassels nearby. Utah State University Extension warns that sweetness is lost if su, se and sh2 types tassel at the same time. Grow only one type in a given planting, or separate plantings so they do not tassel together. Plant in blocks of three or more rows rather than one long row. Ripe ears also draw animals, so see What Eats Corn in Nunavut, and When before you decide how long to leave them on the stalk.
Keeping them, and for how long
Sweet corn loses sugar from the kernel rapidly at high temperatures, so cook it soon after picking. Clemson Cooperative Extension explains why: “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.” That is the old advice about running from the garden to the pot, with the reason attached. Sugar leaves the kernel, and heat speeds it up.
How many days will picked corn keep?
The Clemson wording gives a ceiling. About five days is the most you can expect under optimal conditions, and sweetness drops with every day inside that span. Corn left on a kitchen counter is not under optimal conditions. Neither is a bag in a warm porch. Plan to eat the first ears the day you pick them, and treat anything kept past that as a bonus with less sugar in it.
Cold and moisture are what “optimal” means in practice. The ears should be cold without freezing and kept in the husk so they do not dry out. Clemson does not give a degree reading or a humidity percentage in the passage above, so do not guess at one. A thermometer in the spot you plan to use will tell you more than a rule of thumb.
Does the type of sweet corn change how fast it fades?
It does, and it is the most practical reason to choose one type over another. The three common genetic types lose sugar at different speeds.
| Type | How fast sugar fades after picking |
|---|---|
| su | Fastest |
| se | Slower than su |
| sh2 | Slowest |
An su ear picked in the morning and cooked at dinner is a different food from one that sat for three days. An sh2 ear forgives more delay, which suits a gardener who picks a dozen ears at once rather than a few at a time. The trade-off is soil. The extra-sweet types want the warmer 65 F soil Clemson names, and in a short season that is a real cost.
Heat in the garden is not what the Nunavut crop has to fear. At Rankin Inlet A, ECCC counts 0.0 days a year reaching 32 °C and about 0.03 days a year above 30 °C, a threshold the station almost never touches. Warmth that eats sugar mostly comes from where you set the ears down after picking: a sunny step, a closed car, a warm kitchen. That is a matter of habit, and you can fix it by getting the ears into the cold quickly.
Where in the house that actually is
A domestic fridge is the closest match to what the corn needs. It is cold and holds that cold day after day. The usual catch is dryness, so store ears in a container that holds moisture. Keep them in the husk, and put the husked ears in a sealed bag or container if you have already shucked them.
Which rooms are too warm or too unstable?
A heated room is too warm. A kitchen counter, a living room shelf, or a pantry next to the stove all run well above what slows sugar loss. A porch, an entry or a garage looks promising until you remember how much outdoor air swings in Nunavut. A September afternoon can be mild, and the same space can fall below freezing by night. A frozen and thawed ear loses quality. An unheated space that stays above freezing for a week is a lucky exception.
What should you check with a thermometer?
Before the first ears are ready, put a cheap fridge thermometer in the spot you plan to use, such as the crisper drawer or a lower shelf, and read it after a full day. Some shelves run colder than others, so check the spot before storing a delicate ear. Check the reading before harvest day, because a drawer that runs too warm quietly costs you sweetness each day the corn sits there. If you want to use an unheated space, put the thermometer there too and read it at night and again in the afternoon.
Cooling quickly matters as much as the final temperature. Carry a cooler or a shaded bucket to the garden, pick in the cool of the morning when you can, and bring the ears indoors without a stop in the sun. Corn picked at dawn and cold by breakfast holds its sugar far better than corn picked at noon and left on the counter while you finish chores. For the wider picture of the crop in this territory, start from Growing Sweet Corn in Nunavut.
Common questions
How can I tell sweet corn is ripe without pulling the husk back?
Look at the silks first. They should be dry and brown, while the husk stays moist and green. Then peel back a small strip and puncture a kernel with a thumbnail. Milky juice confirms it. Use all three signs together, because brown silks alone can mislead and clear juice means the ear is not ready.
Is the mean frost date a safe date to plant sweet corn in Nunavut?
No. The mean last spring frost at Rankin Inlet A is June 19, so in half of years frost comes later. The soil also warms well after the frost date. Wait until soil at 4 inches deep is at least 50 F for ordinary sweet corn, or 65 F for extra-sweet types.
How long does picked sweet corn stay sweet?
Clemson Cooperative Extension says sweet corn can be stored under optimal conditions for about five days, and that it loses sweetness with each day of storage. Treat five days as a maximum. The su type fades fastest, se holds sugar longer, and sh2 holds it longest.
Can I plant different sweet corn types next to each other?
Avoid letting su, se and sh2 types tassel at the same time, since that costs sweetness. Plant one type per planting, or stagger the plantings so they do not shed pollen together. Keep the rows in blocks of three or more. Your county extension office can advise on spacing for your own site.