The Christmas tree doctor is in.

Send us Fan Mail When Gary Chastagner was a kid in the 1950s, his parents typically displayed their Christmas tree for about a week. The tree went up on December 24—often after he went to bed—and came down after New Year’s Day. Now, consumers want fresh-cut trees that can be displayed for weeks without losing their needles. Chastagner, a professor emeritus of plant pathology at Washington State…