Gadenin日本語Get the appFeed twice, and time it around knee height and tassel
Sweet corn is one of the hungriest things in a vegetable garden. It is a grass, it builds six feet (1.8 m) of stem and leaf in about eight weeks, and it runs out of nitrogen halfway through if you rely on what you dug in at the start. Two side dressings during the season are the difference between a full cob and a stubby one.
The first goes on when the plants are knee high, about 18 inches (45 cm). The second goes on when you can feel the tassel forming inside the top of the stem, or just as it starts to show. After the silks turn brown, extra nitrogen does nothing for the cob and only makes the plant top heavy, so stop there.
| Stage | What to apply | How to apply it |
|---|---|---|
| At sowing | Compost plus a balanced granular feed | Worked into the top six inches (15 cm) of the bed |
| Knee high, 18 inches (45 cm) | A nitrogen-rich side dressing | A band six inches (15 cm) out from the stem, scratched in |
| Tassel emerging | A second nitrogen side dressing | Same band, then water it in |
| Silks browning | Nothing | The cob is filling from reserves. Feeding now is wasted |
Pale, narrow lower leaves with a yellow stripe running up the midrib are the classic nitrogen shortage in corn. If you see that pattern before tasselling, bring the next side dressing forward rather than waiting.
Hill soil up the stem for anchorage
Corn throws out a ring of thick prop roots from the lowest few inches of stem, above the soil line. Those roots exist to brace a tall plant against wind, but they can only do the job if they reach soil. Draw four to six inches (10 to 15 cm) of earth up around the base of each plant when it is knee high, and again if you see a new ring of prop roots hanging in the air.
Hilling also buries the small weeds growing along the row and gives the plant a fresh layer of moist soil to root into. A block of corn that has been hilled twice will stand through a summer storm that flattens an unhilled block.
- Hill at knee height Draw soil from between the rows up against the stems with a hoe, to a depth of four to six inches (10 to 15 cm). Do it straight after the first side dressing so you bury the fertilizer at the same time.
- Watch for prop roots in the air If you see a new whorl of thick roots arching out of the stem with nothing to grip, hill again. Those roots dry out and die if they never reach soil.
- Stand a leaning plant back up After a storm, push a leaning plant upright and firm soil around the base the same day. Corn that lies over for a week develops a permanent bend and the cob ends up on the ground.
The two weeks around tasselling decide the crop
Corn is fairly tolerant of dry soil while it is young, but from the point the tassel emerges to the point the kernels have filled it is intolerant. Drought during that window aborts kernels outright, and no amount of watering afterwards brings them back. If you water corn only once all season, water it then.
Give it an inch (25 mm) of water a week during that period, delivered in one or two thorough soakings rather than a daily sprinkle. A light watering wets the top two inches and encourages shallow roots on a plant that badly needs deep ones. Mulching the block with straw after hilling holds the moisture and saves you half the watering.
| Growth stage | Water need | What happens if it runs dry |
|---|---|---|
| Seedling to knee high | Low. Rain is usually enough | Growth slows, plant recovers |
| Knee high to tassel | Moderate, about an inch (25 mm) a week | Shorter plants, smaller cobs |
| Tassel and silking | High. An inch (25 mm) a week without fail | Kernels abort. Damage is permanent |
| Kernel filling | High until the silks brown | Kernels stay small and doughy |
Leave the side shoots alone
Short leafy shoots often appear from the base of a corn plant, and gardeners routinely cut them off in the belief that they steal energy from the cob. They do not. Those shoots are called tillers, they carry their own leaves, and removing them wounds the plant at the base and can reduce yield rather than increase it.
Tillers are simply a sign that the plant has room, light and plenty of nitrogen. Leave them. The one thing worth removing is a second or third cob on the same plant if you want a single large one, and even that is optional. Most home gardeners get two usable cobs from a well grown plant and one from a crowded one.
- Ignore the basal tillers Leave any leafy shoot that comes from below soil level. Cutting it opens a wound at the base where rot and borers get in.
- Decide about the second cob early The top cob on a stem is always the biggest. If you want show-sized cobs, pinch off the lower one while it is finger sized. For eating, keep both.
- Keep the block weed free early Corn is a poor competitor for the first month and then shades everything out. Hoe between the rows until the plants are knee high, then stop and let the canopy do the work.
Reading the plant through the season
Corn is honest about its condition if you know where to look. Leaves rolling into tight tubes by midday mean it is short of water, and if they are still rolled at dawn the shortage is serious. Yellowing that starts on the oldest leaves and runs up the midrib is nitrogen. Purple stems on a young plant are cold soil and correct themselves as the ground warms.
- Leaves rolled at midday Normal in strong heat if they open again by evening. If they are still rolled at first light, water the block deeply that morning.
- Yellow stripe up the midrib of lower leaves Nitrogen shortage. Side dress immediately if the tassel has not yet emerged. After silking it is too late to help this crop.
- Plant is short and the tassel is small Usually crowding or a cold start. Note the spacing you actually achieved so you can widen it next season.
- Whole block leaning the same way Wind, and not enough hilling. Stand them up, hill again, and plan a windbreak or a tighter block next year.