Looking After Your Corn

An ear of corn, just picked from the garden, plunged into boiling water, eaten at its peak of sweetness: there’s no more delectable garden treat.

Many home gardeners don’t think they have enough space for corn, but even a ten‐by‐ten foot (3×3 m) plot can produce a nice crop.

Types of Sweet Corn

Choose corn varies by sweetness, days to harvest, ear size, and kernel color.

Within a few hours of harvesting, the sugar in most sweet corn starts turning to starch. Hybrids were developed to address this problem. Sweet corn hybrids are classified by sweetness: normal sugar (su), sugar‐enhanced (se), and supersweet (sometimes called “shrunken” or SH2). The two‐letter acronym refers to the gene. Normal varieties are best eaten straight from the garden, as their sugar turns to starch very quickly after harvesting.

Sugar‐enhanced varieties have more sugar than the normal cultivars and will stay sweet from ten to fourteen days after picking. Supersweet varieties have the most sugar, and will remain sweet for several weeks after harvesting. Supersweets are very popular but are more finicky to grow. Some people think they’re too sweet and don’t taste “corny” enough. Normal varieties are easiest to grow.

Sugar‐enhanced varieties fall in between the two: in sweetness, time to convert sugar to starch, and hardiness.

Open‐pollinated corn has two advantages over hybrids: The harvest comes in over a longer period of time. (Hybrid corn matures all at once.) Also, seed can be saved from year to year. (Hybrid seed can’t be saved, and must be purchased every year.)

Sweet corn is also categorized by days to harvest: early (55 to 70 days), midseason (71 to 85 days) and late season (over 85 days). Early corn generally has the smallest ears, mid‐season ears are larger, and late‐season ears are the largest. Varieties of sweet corn include classic white ‘Silver Queen’ (su, 8′ or 2.4 m tall, 9″ or 23 cm ears, 92 days), yellow ‘Kandy Korn’ (se, 8‐9′ or 2.4‐2.7 m tall, 8″ or 20 cm ears, 89 days), dark purple ‘Hookers’ (heirloom, 4‐5′ or 1.2‐1.5 m tall, 5‐6″ or 13‐15 cm ears, 60‐70 days), and multicolored ‘Rainbow Inca’ (heirloom, 7‐9′ or 2.1‐2.7 m tall, 8‐10″ or 20‐25 cm ears, 75‐80 days).

Growing Requirements

Corn is a warm‐weather crop. Early corn should be planted after last frost, when the temperature is between 55° and 70° Fahrenheit (13°‐21° Celsius). Mid‐ and late‐season corn can be planted at 60°‐80°F (16°‐26°C), but a temperature of at least 65°F (18°C) is preferred.

Corn is a heavy feeder, and particularly needs nitrogen. It likes rich, well‐drained soil with a pH of 6.0 to 6.8. Add lots of compost, plant in full sun, and keep well watered.

In addition, corn is pollinated by the wind ‐ which deposits pollen from the male tassels (on top of the cornstalk) to the female silks (at the top of each ear of corn). There is one silk for each kernel of corn ‐ each kernel must be pollinated for the kernel to form. Corn must be planted in blocks to ensure that pollen reaches each kernel. (This is why you sometimes see ears of corn with incomplete kernels.) Most corn varieties will cross with each other, so if you plant multiple varieties, stagger plantings so that different varieties aren’t flowering at the same time (at least two weeks in between plantings).

Planting Corn

Corn is usually planted in rows or blocks. Plant at least four rows of hybrid varieties, or five to six rows of open‐pollinated varieties, in order to ensure proper pollination. Space plants from nine to 14 inches (23‐36 cm) apart, depending on the size of the mature plant. Plant seeds one inch (2.5 cm) deep in cooler weather, 1.5 to 2 inches deep (3.75‐5 cm) in hotter weather.

One method is to plant two seeds per foot (31 cm), in rows thirty to forty inches (76‐101 cm) apart, in blocks of four rows. Thin to one seed per foot (31 cm) when seedlings are about four inches (10 cm) tall. Early corn grows from four to six feet (1.2‐1.8 m) high and plants can be planted closer together ‐ from 9‐12 inches (23‐31 cm) apart. Mid‐season corn grows from six to eight feet (1.8‐2.4 m) tall and should be planted about 12 inches (31 cm) apart. Late corn may grow from seven to ten feet (2.1‐3.0 m) tall, and should be planted 12‐18 inches (31‐46 cm) apart. Another way to plant corn is in the original Native American fashion: in hills, along with beans and squash. For this method, see the article on “Planting Tips” which discusses intercropping.

Plant corn in your garden, and enjoy the sweetest corn you’ve ever tasted!

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