I used to grown corn every year. It grows very easily here and yeah, you can use dried kernels from store bought corn but you'll have more reliable germination with seed packets because there's a lot of variables with the corn from the store, and you have to dry it for a while. They're very cheap in packets anyway and you don't have to have ears of corn hanging around waiting for them to dry out. Also if you remove the kernels from the ear wrong you could have dead seeds. Another thing to consider is you can buy the flint corn variety seed that has multiple colors in it and I think those look really neat dried.

Anyway, around now is a fine time to start them although they won't grow fast until the night time temperatures are around 60 so you can wait a little if you want. I like to bunch groups of them up as close as possible so the pollen from the tassels doesn't have to travel far. I always get much better pollination when they are bunched up into small groups. You might as well get corn from them if you're growing them.

You can plant them right next to each other and if they start growing at weird angles, just tie the bunch of stalks together as it grows. This'll help achieve the dried stalk bunch look you may be looking for. If you plant them around the start/middle of March, you'll have dried stalks by around the end of June, and you can store them till fall if you want.

The only thing I think that is important as far as growing them, is use mostly native soil for the soil they are planted into. If you put too much compost or loose soil into the area they are planted, they won't grow well and they will fall over from a light breeze.

Also as far as fertilizer goes, I never used fertilizer for corn, although they do need some nitrogen so if your soil is lacking, you will need to add some (you can tell by how the leaves look if they need it or not).

If what you want are the stalks ... any cheap corn seed except the "dwarf" kinds will do. If you have leftover décor corn, plant them in groups of 3 or 4 and snip off all but the strongest sprout.

Plant in blocks for wind defense, or tie them together loosely. 2 feet apart will give them enough room for good leaf development all along the stalks.

When you have nice tall leafy stalks, cut them off and hang them to dry like herbs, or stop watering them and let them die and dry in the ground.