Seeing the Forest and the Trees


Research at Arnold Arboretum
Part 1 of a 2-part series

Courtesy Photo
Researchers Abraham Miller-Rushing (left), Sarah Rathbone and Kiruba Dharaneeswaran collect samples during warm weather from an Arnold Arboretum maple tree as part of a climate change study.

The thousands of visitors who come to Harvard University’s Arnold Arboretum to enjoy its natural beauty often can’t see the forest for the trees.

Famous as one of the jewels of the Boston park system, the arboretum is also the hub of groundbreaking but largely invisible research in such fields as evolutionary genetics and climate change. Its stately trees live a double life as part of an open-air museum of plant life from around the world, continually offering up new secrets to scientists.

The science—including programs everywhere from Cambridge to Borneo—is world-renowned among academics but little-known to most locals.

“There’s a lot of research going on that’s probably not very visible,” said arboretum Director Bob Cook.

Hiding in plain sight could be the arboretum’s theme. The historic Hunnewell Building’s gift shop counter doubles as a reception desk for the arboretum’s surprisingly modern headquarter offices.

Last month, the Gazette met Cook there for an exclusive glimpse at this academic side of the institution. A familiar face at neighborhood meetings, Cook is also a professor who once studied how white violets reproduce by cloning themselves.

We all know what visitors see in the arboretum’s 15,000 trees—beauty, perhaps ecological or environmental benefits. But what does Cook see?

“You see the differences between things and you ask the question, ‘Why?’” he said.

Once again, it goes back to knowledge hiding under our noses, Cook explained.

“There’s a phenomenon that happens every spring that people have become so accustomed to they don’t think about it”—leaves coming out on trees, Cook said. “It’s an immensely important phenomenon we don’t fully understand.”

The biology is obvious in some ways, but not its underlying causes and subtle triggers. For example, Cook explained, maples leaf out around April/May, but oaks wait until around May/June.

“Why should there be a difference here?” Cook said. There are hypotheses, including current climate conditions and evolutionary vestiges. But only research, particularly the exciting and growing field of gene mapping, can sort things out. And that’s exactly the kind of research the arboretum conducts.

Another example: If you pointed out that the arboretum is basically full of wood, and you’re not still in kindergarten, nobody would pay much attention. But, Cook asks, why are trees woody, as opposed to other plants?

“Is woodiness a unique trait, or is it in fact ubiquitous in all species and genes just turn it on and off?” he asked. Evidence indicates it’s the latter, which raises fascinating, basic questions about what turns a plant into a tree.

Maybe the questions sound trivial, Cook allows. But, he notes, there’s no telling where such basic science might lead—perhaps to new breeds of lumber, better understanding of human stem cells, or now-unknown realms of knowledge.

The actual work on plants is totally unnoticeable to visitors, usually consisting at most of scraping off some cells for analysis. But the research end will soon become more visible. Responding to what Cook calls a new era in genetic plant biology, the arboretum is planning a 45,000-square-foot lab and administration building on its Weld Hill parcel.

The building has been controversial, in part for the perception that it is swallowing up the arboretum’s park space. Virtually unmentioned in the debate is what will actually happen in the building.

“It’s an institution as much as a landscape,” Cook said of the arboretum, describing the dual uses as complementary. Referring to the mystery of leaves coming out on trees, he said, “That is an example of what will go on in the future research laboratories.”

A history of discovery
Benjamin Bussey bequeathed the future arboretum land to Harvard, originally for an agricultural college that was established on the current State Lab site in 1871. “It was way ahead of its time,” Cook said, noting that it later became world-famous for groundbreaking genetic studies.

Arnold Arboretum was established in 1872 on land bequeathed by James Arnold as a complement to the Bussey Institute, as it was known. It was landscaped by Frederick Law Olmsted as part of the Emerald Necklace park system. (Harvard donated most of the land to the City of Boston in exchange for an essentially eternal, no-cost lease.) The terms of the donation ordered the arboretum to grow virtually any tree or shrub that can grow in Boston’s climate.

Solving the mysteries of plant evolution was a goal from the start. Charles Sprague Sargent, the arboretum’s first director, was obsessed by the question of why plants in Asia and America were often so similar and able to crossbreed—a particular mystery in the era before DNA and plate tectonics were known. He began a massive program of collecting living plants and preserved samples from both continents.

For its first half-century, the arboretum was famous for discovering new species, identifying plants and establishing its enormous Herbaria, or collections of preserved specimens. The Herbaria, and mwost of the arboretum’s extensive library, have since relocated to Cambridge, becoming in effect invisible to arboretum visitors.

The arboretum’s greenhouses were also famous for propagating new strains of plants, especially flowers, which are always donated free to the nursery industry. Donald Wyman, the head horticulturalist from 1935 to 1970, was “kind of the father of American domestic horticulture—gardening,” Cook recalled. Wyman not only developed new garden plants, but also wrote popular, authoritative gardening books.

A paradigm shift came in the 1980s, with the start of human gene mapping and the vision of then-director Peter Ashton. While the Herbaria were still impressive, Cook said, Ashton “felt the real value of Arnold Arboretum was as a living collection…a pool of species for comparative biology.”

The idea of the arboretum as a kind of genetic museum, a living plant zoo, set the arboretum on its modern course. Today, it is turning its nearly $11 million, self-funded budget toward unlocking the genetic secrets of trees.

Next issue: Arboretum Research: Jungles and Fenway Park.

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