Both Jupiter and Odin lay claim to this tree. They look nice, too. Romans engraved palm fronds on the tombs of heroes to commemorate their victories in North Africa. By 33 AD, the palm was used to greet any popular figure. Christians recognize it as the emblem marking the beginning of the Passion which ended in Christ's victory over death.
Roses signify completion, the achievement of perfection.
The sinless Christian earns for her or himself a rose. The virgin gets a white rose. Perhaps to keep mourners cheered, blue roses seldom appear in cemetery art. In former days, it was put in coffins and given to mourners as a favor. A Japanese herb given as a memoriam offering at temples.