If they are brown or tan don't bother with them. They are dead and rot has already set in. The ones you want will be a more yellow green or olive green color...at least that is how it works here. If the paper sheath is partially or completely deteriorated off they are usually ready to cut. You will know if you have cut immature culms because they will begin to shrivle lengthwise as they dry. You don't need to seal them. Bundle them up in 15 or so per bundle of similar sizes and store them for a month or so in a dry place. I use rubber bands for the bundles but have used string coiled down the bundles.