"When roses bloom in December..."

"When roses bloom in December,
 when pears grow on an apple tree,
 when snowflakes fall in the summer,
 you'll be true to me..."
                                 - Snowflakes in the Summer, sung by the Everly Brothers

Well, I've never seen pears growing on an apple tree, nor have I seen snowflakes in the summer (though I have seen a hailstorm); but I've often and often seen roses blooming in December. Unfortunately, when the hard frosts come the poor little roses get punished for their pains...