The biggest plants in our gardens often get the smallest share of our attention. And it’s not because trees don’t need or want attention — or because we intend to neglect them.
Maybe it’s because they look so strong, holding most of their foliage overhead and not making their needs known near ground level, where we are busy paying attention to everyone else. Or maybe we just don’t have much tree-care confidence.
At The Morton Arboretum in Lisle, Ill., Julie Janoski and her Plant Clinic colleagues respond to gardeners’ and green-industry professionals’ questions — about 17,000 a year. And many of those questions are about trees.
From that sampling, the team can infer that people find trees a little enigmatic.
In 2020, they received calls, emails and visits from residents of 48 states, requesting help with plant and pest identification and treatment, pruning, arborist referrals and more. The questions are answered free of charge by two full-time staff members and about 45 volunteers, many of them master gardeners who receive 30 hours of training at the arboretum, which is about a half-hour west of Chicago and welcomes more than a million visitors a year.
The Morton’s mission is to act as “a champion of trees.” The 1,700-acre institution, preparing to mark its centennial in 2022, is a research center, conservation and educational organization — besides being an arboretum and public garden with more than 222,000 plant specimens representing some 4,650 species and varieties.
Ms. Janoski, a former landscape designer, has been the Plant Clinic manager for three years, working under the mandate she learned as a volunteer for five years before that: “To teach gardeners the best practices in plant care, based on the latest science,” she said, “unbiased and research-backed.”
The Very Hungry Caterpillars
Some questioners arrive in person, bearing exhibits with evidence of the crime.
The other day, a man walked into the clinic with photos of a five-gallon bucket of bagworm bags he had handpicked off a besieged arborvitae. The larvae of these native moths in the genus Thyridopteryx feed on tree foliage, including his Thuja, junipers and even deciduous trees, combining their silk with the foliage to make bags that resemble tiny pine cones. When the larvae mature, they hang the bags from branches and pupate inside.
“Because they use so many needles, between eating and making bags, they can defoliate a tree,” Ms. Janoski said. With evergreens, which don’t regenerate their foliage as often as deciduous trees, this is especially taxing.
Fall webworms (the larvae of another native moth, Hyphantria cunea) are appearing now as well, forming large, gauzy enclosures on the ends of branches of a wide range of plants. The advice: Any harm caused will be cosmetic, so view them as bird food, and don’t panic.