Gadenin日本語Get the appThree phases and one critical week
A sweet corn season splits into three phases: establishment from sowing to knee height, rapid growth from knee height to tasselling, and filling from silking to harvest. The whole crop is decided in the week that straddles the second and third, when the tassel sheds and the silks receive. Everything you do earlier is preparation for that week.
From sowing to first picking is 70 to 100 days depending on type and on how warm your summer is. Because a block ripens within about a week, plan the season around when you want to be eating corn, and stagger two sowings three weeks apart if you want a longer run.
| Phase | Roughly when | What it decides |
|---|---|---|
| Establishment | Sowing to about 30 days | How many plants you actually end up with |
| Rapid growth | 30 to 60 days | Plant height, cob size, wind resistance |
| Pollination | Around days 55 to 70 | How many kernels there are. Irreversible |
| Filling | Silking to about 20 days later | Sweetness and kernel size |
The stage by stage list
The list below is written around your last spring frost and around the plant itself rather than around calendar months, because soil temperature and your own summer heat move the whole thing by weeks. Corn is a warm season crop everywhere it is grown, so the anchor point is always the same: the ground has to be warm before the seed goes in.
If you buy transplants rather than sowing direct, plant them out as small as you can get them. Corn resents root disturbance, and a module-grown plant with three leaves establishes far better than a larger one that has been in its cell too long.
| Stage | Main jobs | The point of it |
|---|---|---|
| Two weeks before last frost | Dig in compost and a balanced feed, cover the bed with plastic | Warm the soil so seed germinates instead of rotting |
| After last frost, soil at 60F (16C) | Sow the block, three seeds per station, net it | Get an even stand of plants in a proper block |
| Two to three weeks after sowing | Thin to one plant per station, hoe the weeds | One strong plant beats two weak ones |
| Knee high, 18 inches (45 cm) | First nitrogen side dressing, hill up the stems, mulch | Fuel the growth spurt and anchor the plant |
| Tassel emerging | Second side dressing, water heavily, stop hoeing | Support pollination and kernel set |
| Silks showing | Hand pollinate on three mornings, keep water up, net against birds | This is the week the crop is decided |
| Silks brown | Clip husk tips, note the date, keep watering | Block earworms and start the harvest countdown |
| 18 to 24 days after silking | Milk test, pick, chill or freeze the same day | Catch the short window at peak sweetness |
| After the last cob | Chop and remove stalks, plan next year's bed | Deny borers and smut somewhere to overwinter |
Early season: get an even stand
The job in the first month is simply to end up with the number of plants you meant to have, evenly spaced. Gaps in a block hurt twice, because they cost you cobs and they thin out the pollen cloud. Net against birds from the day you sow, put collars round the seedlings if you have cutworms, and thin decisively at three leaves.
Weeds matter now and only now. Corn is a poor competitor while it is short, then it shades the ground so completely that nothing else grows. Hoe between the rows every week until the plants are knee high, then stop, mulch, and leave the roots undisturbed for the rest of the season.
- Check emergence at day 10 Walk the block and mark any station that has not come up. If more than a fifth of the block has failed, resow the whole thing rather than patching it, so it pollinates together.
- Thin at three leaves Cut the surplus seedlings off at soil level, keeping the stoutest at each station. Waiting longer means the roots have already knitted together.
- Stop hoeing at knee height Corn roots run shallow and wide. Once the plants are 18 inches (45 cm) tall, mulch instead of hoeing so you do not cut them.
Midseason: feed, hill and then get ready to pollinate
From knee height, corn puts on height fast, and the two jobs of this phase are keeping it fed and keeping it upright. Side dress with nitrogen and hill soil up the stems on the same visit, then mulch. From that point until the silks brown, the block should never be allowed to dry out.
Start watching the tops in the second half of this phase. When the tassel pushes out of the top of the stem you have a few days before the silks appear, and that is your cue to plan three consecutive mornings for hand pollination and to get netting ready for the birds.
- Feed and hill on the same day Scatter the side dressing in a band six inches (15 cm) from the stems, then draw soil over it as you hill. One pass does both jobs.
- Set up the watering before tasselling Have a soaker hose or a plan in place before the tassel shows. An inch (25 mm) a week from tasselling to browning silks is not optional.
- Diarise the pollination mornings The day the tassel opens, block out the next three or four mid mornings. Missing that window cannot be made up later in the season.
Your own dates beat any general calendar
Everything above is relative to your last frost and your soil temperature, but two gardens a few miles apart can differ by two weeks, and a sheltered south-facing bed runs ahead of an exposed one in the same garden. The published day counts on a seed packet are a starting point, not a schedule.
Four dates written down turn this into your own calendar: the day you sowed, the day the tassel first shed pollen, the day the silks first showed, and the day you picked the first good cob. Add a note on where the block stood and how the weather behaved during the pollination week. One season of that record is worth more than any amount of general advice, and it tells you immediately whether to sow earlier, space wider, or split the block into two sowings next year.