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Sweet corn (photo courtesy of Rob D. Brodman)
Sweet corn (photo courtesy of Rob D. Brodman)

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Zone
Zones 2-43, H1, H2
Full Sun
Full
Regular Water
Moderate

Corn

Corn
Poaceae (Gramineae)
Annuals, Vegetables

Sweet corn is the one cereal crop that home gardeners are likely to grow; it requires considerable space but is still well worth planting. 

Plants are usually 5–8 ft. tall. Once standard sweet corn is picked, its sugar changes to starch very quickly; by rushing ears from the garden directly to boiling water, you can capture the full sweetness.

Sugar-enhanced and supersweet varieties of corn are actually sweeter than standard kinds, and they maintain their sweetness longer after harvest because of a gene that increases the quantity of sugar and slows its conversion to starch. A very few people consider these varieties overly sweet.

As one of the principal warm-season vegetables, corn needs heat, but suitable early hybrid varieties will grow even in cool-summer areas. In northern climates and at high altitudes, grow short-season varieties; plant seeds you have pregerminated and grow with black plastic mulch and a cover.

In Hawaii, try varieties developed especially for Island gardens, such as supersweet kinds ‘Waimanolo SS’ and ‘UH-10’.

Corn grows in various soils but does best in deep, rich ones; good drainage is important. Sow seed 2 weeks after average last-frost date, then make three or four more plantings at 2-week intervals; or plant early, midseason, and late varieties.

In Hawaii, you can plant corn year-round. Plant in blocks of four or more short rows rather than in a single long row; pollination is by wind, and unless a good supply of pollen falls on silks, ears will be poorly filled.

Don’t plant popcorn near sweet corn; pollen of one kind can affect the characteristics of the other. For the same reason, some supersweet varieties must be grown at a distance from standard sweet kinds.

Plant in rows 3 ft. apart and thin seedlings to 1 ft. apart. Or plant in “hills” (actually clumps) spaced 3 ft. apart on all sides. Plant six or seven seeds in each hill and thin to the three strongest plants.

Give plants plenty of water. Feed with high-nitrogen fertilizer when stalks are 12–15 in. tall, again when they are 2–2 1/2 ft. high.

Just as a tassel emerges from the stalk, give a good deep watering that thoroughly wets the entire root zone; repeat when silks form.

Don’t remove suckers that appear. Check your crop when ears are plump and silks have withered; corn is usually ready to eat 3 weeks after silks first appear.

To check, pull back husks and try popping a kernel with your thumbnail. It should squirt milky juice; watery juice means that corn is immature, while doughy consistency indicates overmaturity.

Corn earworm is the principal insect pest. There is no simple control. Most gardeners expect some harvested ears to show worm damage at the silk ends, and they just cut off those ends. The prevention (it’s tedious) goes like this: 3 to 7 days after silks appear, use a medicine dropper to put two drops of mineral oil just inside the tip of each ear.

Baby corn. Special varieties that are harvested very early, when the ears are only a few inches long. The tender ears are eaten whole, often pickled or used in salads or Asian cuisine. Plant seeds 1–2 in. apart; thin seedlings to 4 in. apart. Harvest shortly after the first silks appear, which may be only a few weeks after sowing.

Popcorn. Grow and harvest just like ornamental corn. When ears are thoroughly dry, rub kernels off cobs and store in dry place. White, red, and yellow kinds of popcorn look like other types of corn. Strawberry popcorn, grown either for its ornamental value or for popping, has stubby, fat, strawberry-like ears packed with red kernels.

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