When artificial Christmas trees became popular people in south Louisiana began redecorating them as Mardi Gras trees. A Mardi Gras tree is simply a Christmas tree with Mardi Gras decorations.
Before artificial trees the problem of having a Christmas tree last part the Christmas season was unheard of. Now, the problem of a Christmas tree drying out is no longer a problem.
Mardi Gras season starts with the Feast of the Epiphany, which also ends the Christmas season. So, transitioning from one set of decorations to another is easy, the tree will not be displayed between seasons.