10-14-13 The Unlucky Ponderosa

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10-14-13 The Unlucky Ponderosa

October 14, 2013

Mike McTee investigates the sudden death of a four-year-old ponderosa pine

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In early-September, I watched a four-year-old ponderosa pine discolor and die within several weeks along the entrance hedge. I saw no evidence of pathogens.

I excavated soil around the plant and found moist, but rocky conditions (arrows). Roots penetrated through crevices between rocks. Large rocks inhibited free root growth in several directions.

I rinsed the dirt off the tree and found that the roots wrapped around themselves. Perhaps the roots became deformed in their container prior to planting. Lucas, the leader of our annual planting crew, suggested that the rocky soil probably caused this root morphology, which restricted nutrient transport and killed the tree. In other words, the tree girdled itself.

For comparison, I excavated a healthy ponderosa from the same site and found long lateral roots, a deep tap root, and mild tangling. Despite the abundance of large rocks in this hedge, few trees died this year.

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