Candle wick mushrooming occurs when there is excess carbon or incomplete combustion of the candle wax. This usually happens when the candle wick is too long or the candle has been burning for an extended period. The "mushroom" shape at the end of the wick is actually carbon buildup, which can cause your candle to produce smoke or soot. To prevent wick mushrooming, it's important to trim your candle wick to about 1/4 inch before each burn and to avoid burning your candle for more than 4 hours at a time. Using high-quality candles, like beeswax candles, can also help to reduce mushrooming as they burn cleaner and produce less soot than other types of candles.