Most likely last night there were some volunteers in your church. They came in after the last service. For St. Sebastian that would have been after 8:00PM Vespers and Benediction. They carted away all of the plants in the church. The altar clothes were removed and replaced with simple altar clothes. The ones that were removed (for St. Sebastian this would be four of them; great swaths of material from the two altars in use and the two side altars) were taken to be laundered and then (God bless our volunteers) ironed and put into storage. Extra candles and all other decorations were stored away. (I believe in undecorating for Lent.) For those parishes that believe in decorating for Lent, purple banners were put up, dead twigs and other various and sundry things brought out. Green vestments are put away and all of the purples ones are put out and made handy.
Perhaps palms were burned to make ashes. Fr P. called yesterday to say that he had burned his palms. I asked if he were at the hospital. They are then placed in containers so that they may be easily distributed today. A table is probably set up with them and the holy water.
This was all done in order for you to have a Lenten experience when you showed up at Mass this morning. Say a prayer for the gremlins that just make things happen.