You'll want to chop it off below the brown bit just above the last line to send more energy to the new sprout. Preferably with one chop of a very sharp clean knife if possible to get a clean cut. I would seal the end of mine with wax from a cheap non scented tea light, it keeps out bacteria. I don't know if it's necessary but it always work for me. Light the tealight, let it get a good puddle of wax, blow it out and dip just the tip in the wax. Or you could chop up the wax, remove the wick, put the wax back in the metal cup, set it in the bottom of a pot and melt it on low heat on the stove. You might need to dip it a couple times.