Sweet corn

Light and exposure

Sweet corn demands full sun, no compromise. Give it the most open and warmest spot in the vegetable garden, sheltered from strong winds that flatten the tall stalks. Corn in the shade makes neither good stalks nor filled cobs, it just struggles along.

Since the plant often reaches one and a half to two metres, place the corn patch on the north side of the garden so it does not shade the lower vegetables. Be careful, though, that it does not block the wind so much that it hinders pollination, which actually needs a bit of a breeze.

Watering

Sweet corn is thirsty, especially at two key moments: flowering, when the tassels and silks emerge, and grain filling. A lack of water at these stages gives half filled cobs, with rows of missing kernels. Water generously and deeply during dry spells from July to September.

The rest of the time, regular watering is enough to keep the soil cool. A good mulch at the base helps a lot to hold moisture and space out watering, which is precious during the dry summers that come back more and more often here.

Soil and repotting

Corn likes deep, rich soil well supplied with organic matter. An addition of mature compost or well rotted manure in autumn or before sowing supports its fast and voracious growth. It is a vegetable that drains the soil, so give it plenty to feed on.

It enjoys soil that warms quickly in spring and drains well, while staying cool in summer. Heavy, cold soils slow emergence and do not help a plant already pressed by the shortness of our season. A light earthing up at the base during the season strengthens the anchoring of the tall stalks.

Temperature and humidity

This is the sensitive point in Belgium. Sweet corn is genuinely frost tender: the slightest frost kills young plants, and the seed will not even emerge in cold soil below 10 to 12 degrees. Sowing too early means watching the seeds rot in the ground without germinating.

So wait until after mid-May, once the ice saints have passed and the soil has warmed, to sow in the open ground. To gain time in our climate, you can start in pots under cover from late April and transplant after mid-May. The plant then loves the summer heat and sulks during cool spells, hence the importance of early varieties where summer is short.

Pruning and upkeep

Corn is not pruned. You let the stalk rise in a single shot with its plume of male flowers at the top, the tassels, and its cobs that form lower down in the leaf axils. Touching it would only hinder the plant.

Two useful gestures replace pruning. Earth up the base to stabilise the tall stalks against the wind, and leave the tillers in place, those small shoots that sometimes start from the base, because removing them brings nothing and deprives the plant of a little leaf area. Just take off the clearly dry leaves at the end of the season.

Pests and diseases

In our humid climate, watch for corn smut, a fungus that forms grey, swollen galls on the cobs and stalks, and rust on the foliage. A good rotation, not putting corn in the same spot two years in a row, greatly limits these troubles.

As for pests, slugs attack young plants in spring, and birds, crows first among them, love to dig up the sown seeds and peck the ripe cobs. A net over young sowings and close watch as harvest approaches avoid many disappointments. The corn borer, a caterpillar that tunnels into the stalks, remains rarer in the amateur garden but deserves an eye.

Propagation

Sweet corn is propagated only by sowing, every year. Sow in stations of two or three seeds, at 3 centimetres deep, keeping the most vigorous plant after emergence. Space about 30 to 40 centimetres apart, and above all arrange everything in a block of several close rows, not in a single line.

This block business is no detail: corn pollinates by wind, the pollen from the tassels at the top must fall onto the silks of the cobs below. In a square block, the pollen circulates and lands on its neighbours; in a single line, half of it blows away into the void and the cobs stay full of holes. Do not save the seeds of hybrid varieties, they do not come true: buy fresh seed each year.

Month-by-month care calendar

Green Hub tips

• Never sow before mid-May in Belgium: in cold soil the seed rots without germinating, and the slightest frost kills young plants.
• Plant in a square block of several rows, never in a single line. The pollen from the tassels must fall onto the silks of the neighbouring cobs, otherwise the cobs stay full of holes.
• Choose early varieties: our summer is too short for late ones, which get caught by the cold before filling their cobs.
• Harvest when the silks turn brown and a crushed kernel releases a milky juice, then cook quickly: the sugar turns to starch within the first hours after picking.