Extreme cold event challenges tree trials

By Jay Weiss, Cambridge Tree Project, www.cambridgetreeproject.org

Red horse chestnut, Cambridge

It was a cold, still night January 31, 2019 when the air temperature dropped to -32 in Cambridge, Wisconsin. According to village elders, the last time it got that cold was the 1950s.

With this record setting event, we had a rigorous laboratory to assess hardiness among the wide variety of tree species under evaluation in our trials.

Immediately below is a written summary of some our findings. Detailed survival rates, along with annual growth rates of 98 species being evaluated locally, are recorded in an excel document that I am happy to share upon request (email me at info(at)cambridgetreeproject.org).

SURVIVORS:

  • Bald Cypress: all 26 of our street and park trees survived. No dieback was noted.
  • Dawn Redwood: 11 trees survived with no dieback. Two trees were killed outright.

  • Dogwood, Cornelian Cherry: eight of eight trees survived unscathed
  • Goldenrain: dieback of pencil diameter branches was noted on all four of our ten year old trees. 11 juvenile trees were decimated.
  • Paw Paw: none of our four trees experienced any degree of dieback
  • Persimmon: 12 of 13 trees survived with no damage
  • Pecan: no dieback noted on any of our four pecan trees
  • Sassafras: our two trees experienced no dieback
  • Sweetgum: no issues with all three ‘Moraine’ and all four of our ‘Worplesdon’ cultivars. Results of species sweetgums were mixed.
  • Sycamore: 26 of 27 trees survived untouched by the cold
  • Tuliptree: all 18 tulip poplars survived. Light tip dieback was noted on several trees.
  • Yellowwood: ten of 11 trees experienced no dieback

MIXED BAG:

  • London Planetree: 32 of 57 trees survived. The ‘Exclamation’ cultivar significant outperformed ‘Bloodgood’.
  • Scholartree: four of 13 trees died to the ground. All fatalities were located in compacted soil. Remaining trees planted in better soil suffered no dieback, even on the smallest branches.

NOT HARDY:

  • Dogwood, Kousa: all three trees were killed to the ground
  • Hardy Rubber Tree: our one tree was not hardy
  • Maple, Japanese ‘Bloodgood’: Two of three trees died to ground
  • Zelkova: six of eight trees died to ground

Jay Weiss is the founder of the Cambridge Tree Project, a Wisconsin nonprofit that sells a diverse mix of trees at its annual tree sale. The profits are used to purchase trees for Cambridge schools, streets, and parks. Today, 156 tree species are growing in Cambridge (up from 35 species in 2004). Learn more at cambridgetreeproject.org.

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