Denver’s Polar Plunges

The Denver area is known for its polar plunges that freeze damage trees. The plunges usually happen in the fall but also occur in late spring. The Denver area experienced plunges in October in both 2018 and 2019. It is sunny and warm; then it drops to close to zero or below in a matter of hours. Homeowners that did not blow out their sprinkler systems find geysers of water shooting out in their yards. The lucky ones are home and turn off the water. Those out of town, sometimes come home to a flooded basement.

Trees are caught off guard too by these freezes. The warm weather delays a tree’s hardening process to prepare for winter. Deciduous trees harden by sealing off where leaves attach to the tree. The leaves turn color and eventually drop. Dormancy conserves water and food for the next growing season. Evergreens hibernate in the winter but keep their needles. Non-hardened trees flash-freeze when the temperature abruptly drops. Early fall and late spring freezes affect Elms, Hybrid Cottonwoods, and Bradford Pears in the Denver area.

Testing For Tree Freeze Damage

Some trees show damage immediately, while others will not show damage until the spring. Be sure to water the trees in the winter and hope for the best in the spring.

  • Evergreens – An early freeze kills the new needle growth on Pine and Spruce trees. The needles turn brown. Most of these trees recover as new needles emerge in the spring, but some are lost and need tree removal. 
  • Deciduous – Frozen leafed out deciduous keep their foliage over the winter. These brown, dry leaves drop off during the next growing season. Fruit trees may show individual twig dieback.
  • Newly Planted Trees – Unfortunately, many newly planted trees die after a sudden freeze. It takes an arborist to check if the trees are viable.

To test for freeze damage, gently press the tree’s buds between your thumb and finger. If the buds are soft, they are still alive and will produce new growth. If the buds are dry and brittle, they are dead. 

Most trees will repair themselves, so wait until new growth appears. The new growth dictates the type of pruning required. Need help saving a frozen tree? Our three arborists are at your service.