"At Christmas the wreath is symbolic of Christian immortality. The circle and the sphere are symbols of immortality. Traditionally, the wreath has been worn at festivals, at sacrifices, at weddings, and banquets. The priests wore henbane, vervain, and rue, plants long associated with the other world and religious rites. Crowns for victors were made of laurel (Laurus nobilis), oak, olive, parsley, palm, and poplar. Brides wore coronets or orange blossoms, myrtle, or rosemary. Funeral wreaths were made of daffodils, poppies, and other plants that meant remembrance or everlasting life, as amaranth, statice, tansy and yarrow."
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"The origins of the Advent wreath are found in the folk practices of the pre-Christian Germanic peoples who, during the cold December darkness of Eastern Europe, gathered wreaths of evergreen and lighted fires as signs of hope in a coming spring and renewed light. Christians kept these popular traditions alive, and by the 16th century Catholics and Protestants throughout Germany used these symbols to celebrate their Advent hope in Christ, the everlasting Light. From Germany the use of the Advent wreath spread to other parts of the Christian world. Traditionally, the wreath is made of four candles in a circle of evergreens with a fifth candle in the middle. Three candles are violet and the fourth is rose, but four white candles or four violet candles can also be used. Each day at home, the candles are lighted, perhaps before the evening meal-- one candle the first week, and then another each succeeding week until December 25th. A short prayer may accompany the lighting of each candle. The last candle is the middle candle. The lighting of this candle takes place on Christmas Eve. It represents Jesus Christ being born."
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More information on the history of wreaths as symbols of eternal life can be found at these sites:
https://www.santasquarters.com/origins-christmas-wreaths/
https://time.com/5482144/christmas-wreath-origins/