From The Collaborative International Dictionary of English v.0.48:
hayseed \hay"seed\ n.
1. a rural, unsophisticated person; also used in an extended
sense for one who is not very intelligent or uninterested
in culture.
Syn: yokel, rube, hick, yahoo, bumpkin, chawbacon.
[WordNet 1.5]
2. Seed from grass, especially that which falls out of hay.
[PJC]