98. Placing four candles on green fronds has become a symbol of Advent in many Christian home, especially in the Germanic countries and in North America.
The Advent wreath, with the progressive lighting of its four candles, Sunday after Sunday, until the Solemnity of Christmas, is a recollection of the various stages of salvation history prior to Christ’s coming and a symbol of the prophetic light gradually illuminating the long night prior to the rising of the Sun of justice (cf. Ml 3,20; Lk 1,78).
I have seen many variations on this theme in churches over the years. Perhaps the most impressive was an eight-foot plywood circle wrapped in chicken wire, hung on a wall, and stuffed with evergreens. Candles were in stands in front of it. In other parishes, I’ve seen a huge wagon wheel used, also just a tracing of greens on the floor in a large narthex. And of course, dining room-sized pieces nudged into large churches.
The way the liturgy stands today, the wreath is optional for Advent, not required. Ever been in a church that opted out?
The Directory on Popular Piety and the Liturgy is online at the Vatican site.