To make scale miniature corn cobs for your corn stalk, begin by taking small amount of cotton batting and rolling it into a pointed bud shape with a fatter rounded base. Your bud shape should be equivalent in scale to 9 inches in real length. For a 1:12 scale cornstalk this will be 3/4 of an inch or so long. (see photo) These shapes don't need to be exact, they will form a sort of stuffing for a miniature corn cob. On a corn stalk, corn cobs are always wrapped with leaves and the cobs are not visible.(unless the raccoons have been at them)
Make two or three corn cob shapes for each stalk. This is a fiddly bit which may not be an important detail in your scene. If you have difficulty making corn cobs, you can only have one or two on a plant, or avoid them altogether. (All your corn will have been harvested, or isn't visible yet!)
