Lo how a rose e'er blooming
From tender stem hath sprung
Of Jesse's lineage coming
As men of old have sung
It came, a flow'ret bright
...Amid the cold of winter
When half spent was the night.

There were roses in ancient Israel at the time. Contemporary with the day of his birth. Rosa sancta, Rosa damask. You can still find these varieties. In the Mediterranean climate often a rose blooms thru the snow.