Growing Corn

Corn is wind-pollinated - pollen falls from the tassel (top) onto the silks (ears) below. Each silk connects to one kernel, so every silk must be pollinated for a full ear. This means corn must be planted in blocks (at least 4 rows wide), not single long rows, for adequate pollination. Poorly pollinated ears have gaps of missing kernels.

For sweet corn, choose varieties based on your eating preference and season length. Early varieties (60-70 days) include Early Sunglow and Spring Treat. Main season (75-85 days) includes Silver Queen, Bodacious, and Incredible. Keep sh2 supersweet varieties isolated by 25 feet or 14 days from other corn types to prevent cross-pollination, which makes supersweet starchy.

Corn is a warm-season crop - do not plant until soil temperature reaches 60°F (65-70°F for sh2 supersweet types). In temperate climates, this is typically 1-2 weeks after the last frost date. In tropical regions, corn can be planted at the start of the rainy season or year-round with irrigation.

Corn is a heavy nitrogen feeder. Before planting, incorporate 2-3 inches of compost and 30-50 lbs of nitrogen per acre (or 1 lb per 100 sq ft for gardens). Sow seeds 1-1.5 inches deep, 8-12 inches apart in rows 30-36 inches apart. For the Three Sisters system, plant corn in clusters of 4 seeds on 4-foot mounds, with beans 6 inches from corn stalks and squash between mounds. Thin to 1 plant every 12 inches after emergence.

Corn has three critical water demand periods: germination/emergence, tasseling/silking (pollination), and kernel fill. Water stress during tasseling can reduce yields by 50% or more. Provide 1-1.5 inches of water per week, increasing to 2 inches during tasseling and kernel fill. Drip irrigation with lines between rows is efficient; overhead irrigation during tasseling can wash pollen off silks.

Side-dress with nitrogen when plants are knee-high (V6 stage, about 12 inches tall). Apply 20-30 lbs nitrogen per acre alongside the rows. Organic growers use blood meal, feather meal, or fish emulsion. A second side-dressing at tasseling boosts kernel fill. Corn is also responsive to zinc - foliar zinc spray at the 4-6 leaf stage prevents common deficiency symptoms (white striping on leaves).

Corn earworm (Helicoverpa zea) is the most common sweet corn pest - larvae enter through the silk and feed on the ear tip. Apply Bt (Bacillus thuringiensis) spray to silks every 3-5 days during silking, or apply a few drops of mineral oil to the silk channel 3-5 days after silks appear. Some gardeners clip silks after pollination to reduce earworm access.

Fall armyworm (Spodoptera frugiperda) is devastating in tropical regions - larvae feed in the whorl (growing point), often destroying the developing tassel. Scout by looking for fresh frass (sawdust-like droppings) in the whorl. Apply Bt or spinosad when larvae are small. Weeds are the main competitor during corn's first 4-6 weeks - cultivate shallowly or mulch between rows during this window. After canopy closure, corn shades out most weeds.

Sweet corn is ready 18-24 days after silks appear, when silks are brown and dry. Test by peeling back the husk tip and pressing a kernel - it should release a milky juice. Watery = too early; doughy = too late. Harvest in the morning when sugars are highest, and eat or refrigerate immediately (su types lose sweetness within hours of picking).

Field corn / grain corn is left on the stalk until the plant is brown and dry, and kernels are hard with less than 15% moisture. This takes 4-6 weeks longer than sweet corn. Test by pressing your thumbnail into a kernel - if it dents but does not crush, moisture is in the 20-25% range. Dry further in cribs or bins with airflow until 13-14% moisture for storage.

The Three Sisters polyculture - corn, climbing beans, and winter squash - is an Indigenous American agricultural system that maximizes yield per unit of land through synergistic companion planting. Corn provides the trellis for beans. Beans fix nitrogen that feeds the heavy-feeding corn. Squash spreads along the ground, shading soil to suppress weeds and retain moisture.

Timing is critical: plant corn first and let it reach 6 inches tall before planting beans at its base (otherwise beans outpace corn). Plant squash between corn mounds at the same time as beans. Use pole bean varieties (not bush) and vining winter squash (butternut, hubbard) for the traditional system. Modern adaptations space Three Sisters in wider rows accessible by equipment.