One of the best treats to come out of the garden is freshly grown corn. Since the sugars in sweeter varieties are best enjoyed soon after picking, proximity to home is important; the amount of time lapse between harvesting and eating influence the quality of the flavor. Early planting is not as critical an issue for the home gardener as it is for a farmer looking to plant acreage. That said, the earlier you plant, the more corn you can enjoy across the season through successive plantings.
End to Frost
Watch for rising soil temperatures. Some agricultural authorities suggest waiting until after the freeze date for your area passes to plant, but the University of Illinois Cooperative Extension suggests checking the soil temperature at 7 a.m. at a depth of 2 inches and put off planting if the temperature reads under 50 degrees.
Another school of thought notes that some hybrids are not as delicate as older varieties once were and these can be planted earlier in the year, without as great a risk of damage. The seed and eventual seedling remain protected under the soil, unharmed by temporary late-season temperature dips. The University of Illinois Extension Service lists Sundance and Pearl White as varieties that can tolerate cooler soil conditions.
Do not plant unless the soil is reasonably dry. Soggy, wet soil is not only difficult to work with, it is not good for seed. Planting early may be just the right bet in areas prone to seasonal rains that will prevent you from getting into the garden later in spring. Planting early can also help you beat some of the pest issues that come as temperatures warm.
Plant corn 7 to 10 days in advance of the last frost date or plant earlier with the addition of a protective barrier, such as plastic wrap or sheeting, over the rows. The University of Illinois Extension Service suggests that an early maturing variety be used in this situation.
Phenology is the science of relationships between periodic biological events. This method was developed from environmental observation. It suggests that gardeners not depend on a strict date, but an interpretation of the events occurring in the local area, according to Jerry Clark of the University of Wisconsin Extension, Chippewa County. Regarding corn, the wisdom is that when oak leaves are the size of a squirrel's ear, it is time to plant. This particular example comes from Native American cultivation knowledge.