Does your Christmas tree have good genes?

A plant pathologist discusses why some Christmas trees seem to shed needles more than others.

Vocabulary: conifer, needle dropping, genetics, species, ethylene
 NGSS: LS1.A: Structure and Function, LS3.B: Variation of Traits, SEP3: Planning and Carrying Out Investigations

Madereugeneandrew/ Wikimedia Commons/CC-BY-SA-3.0

One sign of the Christmas season is the tree lots that start popping up. Each person has ideas about what makes the perfect pine or a festive fir — a conical shape, a sharp woodsy smell, or an apartment-friendly size, perhaps. Plant pathologist Gary Chastagner is studying one trait in particular: how well trees hold onto their needles. Conifers, for example, shed their needles for various environmental reasons. Chastagner shares what trees are better at retaining their foliage, along with tips for caring for your Christmas tree.

Audio Excerpt “Does Your Christmas Tree Have Good Genes?” 12/16/2016. (Original Segment)

Print this segment transcript.


  • Should people water their Christmas tree? Why?
  • Describe the factors that can affect the rate of needle dropping in a Christmas tree.
  • How do you think needle dropping protects the tree?
  • Design a test for the fruit basket hypothesis. Will a fruit basket cause more needle loss on a Christmas tree? Be sure that you are able to isolate the effect of the fruit basket.

Activity Suggestions

  • Test the effect of ethylene on fruit ripening (and rotting) by adapting this experiment on apples. Discuss how you might test the effect of ethylene on other types of plants, like trees. Great opportunity to have students examine differences between plant types or different types of tissues in plants.
  • Look more at the effect of water on plant cells with this investigation on mushy apples.
  • Need something to do with all those dropped needles? Explore combustion using festive fuels such as fir, pine, spruce, and cedar.