For most of our characters in the 19th century they enjoyed and needed to plant their own food. Corn was a staple in most homes and farms. Below are some brief tidbits about when to plant corn.
In a 1828 source it is recommended to plant corn on Long Island, NY from the 10th-20th of May.
In 1845 an individual began planting corn in April. Unfortunately it doesn't say where.
An 1854 also says from 10-25th of May.
In a 1895 source it recommends to plant corn when the white oak leaves are as big as a squirrel's foot or a mouse's ear. For New England and Middle states.
Of the various sources I read, most prepared the field by laying down the manurer a month before.