Planting and Spacing Sow or plant corn directly in the garden two weeks after all danger of frost is past and the soil has warmed to 60 fahrenheit. In cool regions and where cool weather persists, spread black plastic on the planting area to speed ground warming, or sow seed in sun-warmed ridges about 3 in. above the planting bed. Protect young seedlings from chilly nights with a floating row cover. Early in the season, sow corn seeds 1 in. deep; after the weather has grown hot in mid-summer, sow corn 3 to 4 in. deep. Set seed 2 to 3 in. apart in rows; space rows 30 to 36 in. apart (closer spacing will result in smaller ears at harvest). Make successive sowings every 2 to 3 weeks for a continuous harvest summer into fall or plant early, midseason, and late varieties at the same time. Weeding Corn is shallow rooted; competing weeds can rob corn of nutrients and moisture. Keep weeds out of the corn patch especially during the first month of growth. After that, control weeds by applying thick mulch of compost. A cover crop of nitrogen-setting clover planted a month after corn is planted will also keep weeds down. Watering and Fertilizing Keep corn evenly moist and regularly watered. Corn grows fast in hot weather and requires an even supply of moisture to avoid wilting. Avoid overhead watering particularly when tassels appear; water hitting the tassels at the time of pollination can reduce the number of kernels on a cob. Add aged compost and aged manure to planting areas the autumn before planting. Corn is a heavy nitrogen user. Side dress corn with aged compost or compost tea when stalks are 10 in. tall and again when they are 18 in. tall and a third time when they tassel. Harvest Harvest is near when ears are plump and silks have withered, about three weeks after the silks appear. To know when to pick corn apart from ears being plump, pull back part of the husk and pierce a kernel with your thumbnail. If there a milky juice spurts out, the sweet corn is ripe. (If the juice is watery, the corn is immature. If the juice is pasty, the corn is past its prime.) Corn is at is peak of sweetness for two to five days. Corn is ready for harvest when ears turn dark green, silks turn brown, and kernels are soft and plump; squeeze a kernel and the juice will be milky, not clear. Pick corn by grabbing the ear and giving it a sharp downward twist. Each stalk of corn will produces one or perhaps two harvestable ears of corn. Harvest usually comes about 20 days after the silks appear. Harvest corn in the morning and plunge ears immediately into cold water to preserve sweetness.