CornBackyard gardeners growing heirloom corn are rewarded with a fresh picked flavor that’s second to none.

Sunlight: Full sun
Maturity: 65-90 days
Height: 4 to 6 feet
Spacing: 8 to 12 inches apart, 2 to 3 feet between rows

Native to North and South America, corn — or maize — was first cultivated some 4,000 years before Columbus set foot in the New World. Today, with more than 85% of the US corn crop genetically modified it’s more important than ever for home gardeners to grow corn and preserve the good, old fashioned heirloom varieties that so many generations have enjoyed eating right off the cob (see Sweet Corn: Hybrid and Heritage).

Fact: The United States produces about 40% of the world’s corn supply on 90 million acres, most of which is grown in the midwest.

Site Preparation:

Corn is a warm-season vegetable that requires full sun, ample water and deep rich garden soil to perform well. Prepare the planting site by working in generous amounts of a quality organic compost or well aged animal manure. Corn needs to be well protected from frost.

Tip: Cover the planting area with black plastic for two to four weeks prior to planting to warm the soil and improve germination. Corn will not germinate if soil temperatures are below 55˚F.

How to Plant:

Heirloom CornCorn should be planted directly into the soil after it has warmed in the spring (two weeks after your average last-frost date). Sow seeds 1 inch deep, 8-12 inches apart. Corn is wind-pollinated, so plant in short rows or blocks to ensure even pollination. Undeveloped kernels indicate uneven pollination. Plant a new crop every two weeks to ensure harvest throughout the gardening season. Corn is a heavy feeder. Fertilize with alfalfa mealblood meal or other high nitrogen organic fertilizer until tassels develop.

Consider adding kelp meal to vegetable gardens. It’s chock-full of micro-nutrients and is especially good for supplying trace minerals to crops that will be consumed. Will also help guard against plant stresses such as insects, frost, disease and drought.

Make sure that the entire root zone is damp as corn ears mature. Water at the base around stalks. Soaking the leaves rather than the roots washes away pollen, and reduces the number of kernels that develop.


Corn is ready to harvest three weeks after tassels appear. Look for dark green husks, brown supple silks and plump kernels that squirt “milky” liquid when pinched. Corn tastes best when it is picked in the late afternoon and should be twisted from the plant in a downward motion. Sweet corn requires 65-90 days to reach maturity, depending on the variety.

Insects and Diseases:

Rotate corn with other crops to prevent recurring pest or disease problems. Corn earworm, deer and raccoon are common pests of corn. Discourage animal pests with fencing, repellents and scare devices.

Spinosad is a relatively new biological pesticide that can be used to effectively combat earworms on corn. Mix 4 Tbsp. per gallon of water and treat silk frequently as it grows. Approved for organic use, spinosad — the active ingredient in Monterey Garden Insect Spray — does not significantly impact beneficial insects and spiders while controlling pests.

White or grayish swellings are signs of corn smut. A common fungal disease that should be treated with organic fungicides.

Seed Saving Instructions:

All heirloom varieties are wind pollinated and will cross-pollinate with each other. Varieties should be hand-pollinated or isolated by one mile to ensure purity. Allow ears to dry on plants, harvest and shell.

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