New to gardening... a quick question:

I planted sweet corn (in Connecticut) and it literally shot up to about 4.5 feet in a month. There are now some brown long things growing out of the top (I assume that is a good thing). I have read that at this stage it is essential to water and give fertilizer to the plants. Is this true or will it do fine on its own as it has been? Also when should I expect corn to start growing? Thanks for the help and advice.