poorly planned tree plantings that end up needing complicated tree care. “Tree work is an aerthought,” Burley said, regarding Norfolk Island pines. “There is little proactivity from the homeowner side.” 7. EASTERN WHITE PINE The final contender for most difficult trees to manage is perhaps the most common: Eastern white pines ( Pinus strobus ). Unlike other challenging spe- cies on this list, it’s a functional conifer native to the U.S. These characteristics would typically make it relatively easy to care for if it weren’t for one issue: “White pines are in decline due to cli- mate change,” Brewer said. It isn’t the rising temperatures that are directly affecting this species though. Rather, the culprit is the balmy condi- tions that follow. “The constant humidity is causing na- tive fungi to grow exponentially.” One such fungus is needle cast which causes the needles of pines, firs, and spruces to brown and drop premature- ly. This fungus thrives in warm, wet conditions, particularly in the summer and fall when temperatures reach 77 degrees Fahrenheit. Infected trees will experience needle drop beginning in
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Constant humidity due to climate change is causing native fungi to grow exponentially on the eastern white pine.
the lower branches before the fungus works its way to the top. Once the nee- dles die, it isn’t long before the branch- es follow. Treatment for these pines isn’t brief. As Brewer explained, needle cast fun- gi require consistent treatment — up to three or four sprays each spring — in- definitely. This level of care then raises questions around the sustainability and ethics
of tree care. As the treatment for this fungus may take several seasons, this gives time for the surviving spores to spread to new trees during wet weather and continue the decline of the forest. “There’s no permanent solution for it,” Brewer said. “It’s not only can you do it, but is it ethical?” EVERY TREE IS HAZARDOUS While these specific species are partic-
Honorable Mentions
While these species didn’t make the list, they still pose their own challenges and should be carefully monitored. Eucalyptus — Common along the West Coast, eucalyptus grows rapidly and can reach impressive heights. In residential settings, their size, brittle wood, and heavy limb drop make them difficult to manage, particularly in confined backyards or near structures. Black Walnut — Known for producing juglone, a chemical that inhibits the growth of many surrounding plants, black walnut can complicate landscape planning. Its dense canopy, large nuts, and extensive root system can also create maintenance challenges. River Birch — A fast-growing species that often develops multiple stems and uneven branch structure. Without proactive pruning, these trees can experience structural weaknesses that require ongoing management as they mature.
Needle cast, a fungus which causes the needles of pines, firs, and spruces to brown and drop prematurely.
ArborTIMES ™ Spring 2026 | 13
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