Here is some advice from Philip Hall on making cornfields for your miniatures waraming terrain.
Check out a craft store that sells artificial flowers. Hobby Lobby is a good place. Look for astibile. This is a plastic plant with small bits of foam glued to it. There are usually various colors most usually yellow and white but purple is a possiblility. The foam comes off easily and you are left with what appears to be a corn stalk. The “leaves” droop appropriately and they appear to have a tassel. A quick dusting with a darker green or tan will take the shine off, or you can just Dullcoat them. They will be to tall, but are easily cut down. I mount them on a 1″by 2″ length of Foamie, putting 8 to a stand. When placed together you can remove the stand that your people are in while leaving the rest of the cornfield intact. Looks good that way. If you aren’t dead set on a cornfield look for a plastic grass welcome mat and cut it into sections. Makes a good “crop” field.
I have also seen and played in a cornfield setting that used wire Christmas garland cut to appropriate lengths and inserted into 1″x2″ stands made of balsa. It worked well and looked pretty good as almost half the table was covered in it.