Meet the Trees: Gingko Biloba

 

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By Sherley Smith

The ginkgo tree is the oldest living tree species in the world. It is a botanical “living fossil,” dating to the time of the dinosaurs -250 million years ago. It was the very first seed-producing tree, which means it was the first tree that could live and reproduce on land. Ginkgo biloba is a “single species,” which means it has no living relatives, and fossil ginkgo leaves have been found on every continent, but the tree primarily survived in the protected valleys of China.  In the eighteenth century, European visitors discovered the ginkgo on the grounds of Buddhist temples in China, Japan, and Korea.

Ginkgos are well represented in two of our parks, with thirteen gingko trees on Boston Common, and eight in the Public Garden, both male and female trees. The first Ginkgo biloba in the parks was transplanted to Boston Common near the Joy Street steps in 1835. Already 40 feet tall at the time, that tree was moved to the Common from the nearby estate of Mrs. Gardiner Greene, daughter of John Singleton Copley.

The male tree produces small, cone-like structures that hold pollen. When female trees are about 25 years old, they produce small fruits with a fleshy, apricot-colored skin around the nut inside. The pulp is quite pungent when mashed and has a strong odor that many find unpleasant.

Long valued for aesthetic, religious, and medicinal reasons, it is said that Confucius studied under a ginkgo tree, giving it special meaning to Buddhists. The nuts are thought to have healing properties and can be eaten as a special delicacy. Extracts of the leaves are also used in medicines to enhance memory or stimulate blood flow.

Due to its resilience, the ginkgo has become a popular ornamental tree in the last fifty years. The tree tolerates pollution, extreme temperatures, road salt, and the confinement of being planted along a street. It is also both pest- and disease-resistant. It is easy to see why the tree is a symbol for longevity in Asia. There is an individual Chinese ginkgo said to be 3,500 years old.

The ginkgo is easy to identify due to its unique, fan-shaped leaves, with veins that fork outward from a central point. Its common name is “maidenhair tree” because the leaves resemble the leaves of a maidenhair fern. Carl Linnaeus, the renowned Swedish naturalist, gave the tree its Latin name, “Ginkgo Biloba,” which refers to the lobed shape of its leaf. In autumn, the leaves turn a beautiful golden hue before falling to the ground, typically all at once, resulting in a wonderful carpet of yellow surrounding the tree

Look for the ginkgos as you walk in the Public Garden and the Boston Common.

 

 

 

Buds and Bulbs: Impact of Late Season Snow

By Claire Corcoran

What impact, if any, will the recent late-season snow and sudden unseasonably cold temperatures have on our trees and shrubs in Boston’s parks? It’s an interesting question with several levels to look at. Most visibly, the magnolia blooms that we enjoy each year were burned by the snow and cold temperatures that followed. If you look closely at the magnolias along Commonwealth Avenue Mall and in the Public Garden, they may have flowers, but most of them are not looking great. Many magnolias had already pushed out their flower buds and hadn’t quite opened IMG_6520when the snow and cold temperatures hit them with frostbite. Magnolias are a southern species, very near the northern limit of their range here in Boston, and their flowers simply can’t withstand the cold. The emerging leaves will push off the wilted flower buds, but the trees are none the worse for it, thank goodness.

 

Many other groups of plants with more northerly ranges have more ability to withstand the cold temperatures. The cherry blossoms have flushed out like any other year, seemingly unaffected by the April snowfall and cold—though this may be more the happy result of naturally later blooming than it is a show of their New England hardiness. Many spring bulbs managed to bounce back from the snowfall impact, and make it look like it never happened. These daffodils in the Public Garden looked unhappy in the snow, but a week later they had completely bounced back. (Photos) My neighborhood Redbud (Cercis canadensis) appears to be on the brink of a record-breaking floral show – a testimony to last springs’ rainfall and snowmelt, rather than present conditions. Apples and crabapples bloom a little later in the spring, and so their flower buds weren’t impacted by the snowfall.

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The late season snowfall and subsequent cold temperatures can actually help some parts of plants “wake up” after this mild winter.  The dormancy of buds, those bundles of tissue that are the precursors of leaves and flowers, occurs in three phases – the pre-dormancy period in the fall, of warm days and cool nights; the deep cold of winter, and the return in the spring to warm days and cool nights that signals the end of the winter.  During a mild winter season, that middle period of prolonged deep cold temperatures doesn’t really occur, leaving a muddied signal in the spring.  Perhaps the plants feel a bit like we humans after a night without enough deep sleep.  Plant physiologists theorize that a late season period of extreme cold, with warmer daytime temperatures, will allow dormancy in this phase to more readily break, and allow the tree to get off to a brisk start in its growing season. Also, the snowfall from the recent storm was likely a benefit to tree roots during the subsequent below freezing day, providing an insulating blanket to protect the below ground fine roots, which are actually more at risk from the cold, and more essential to the plant than its floral show.

 

Fortunately for the trees, and those who care for and about them, the snowfall was unlike that memorable Boston blizzard of April 1, 1997—it was far less significant in accumulation, and didn’t cause the extensive damage to trees and shrubs that that storm caused. Magnolias aside, it seems as if the snow and cold temperatures will have little lasting impact, leaving us still several weeks ahead of normal bloom times as a result of our mild winter.

Meet the Trees: The Beeches

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In midwinter it is not uncommon to have intermittent mild days that tantalize us with reminders of spring. Walking through a park on a warm February day, we might even look to the trees for some confirmation that spring is around the corner—a swelling bud or hint of green, perhaps? Alas, all we’ll note are markers not of the season to come but of the season past: some branches retain from the fall a few straggling, brown leaves. In Boston parks, the only trees that do this are beeches and oaks—both in the same family: the Fagaceae. The botanical word for leaves that remain on trees well into or through the winter is marcescent (from the Latin marcere, meaning enfeebled or withered). Such papery leaves hold fast until the wind rips them free, or until the emerging bud of the spring leaf pushes them off. Scientists speculate that the abscission layer, which forms in most deciduous trees to cut leaves off in the fall, is delayed for some of the leaves of beeches, resulting in a characteristically half-dressed look. In the wild, American Beeches (Fagus grandifolia) form mature forest in parts of central New England alongside Sugar Maples (Acer saccharum). These forests are strikingly beautiful as the Beech often reproduces vegetatively, through sprouts from roots or from rooted branches. This can result in a mother tree surrounded by her offspring in a circle, or, if she is dead, a perfect circle of beech trees of uniform age—a fairy circle in the forest.

All but one of the beeches in our Parks, however, are cultivars of European Beech (Fagus sylvatica). There are some striking horticultural forms represented in the collection, including the Pendula cultivar, with weeping, sweeping limbs; the Rotundifolia, with dark blackish-green leaves and a beautiful, round canopy, and the Asplenifolia, or fern-leafed variety, with lacy cut leaf margins: and the Spaethiana,which holds its deep purple color longer and emerges in the spring with a rich burgundy color. It is fitting that the sole American Beech in our parks is found on the Boston Common, just north of the Frog Pond, as one looks toward Beacon Street.

The Friends of the Public Garden cares for 14 Beech trees in the Garden, some of which date back to the original plantings during the 1870s. These older specimens are special both because of their age and size, but also their placement—three of the oldest are near the Bagheera and Triton’s Baby’s fountains near the mid-block Charles Street crossing. One venerable specimen reaches out over the pathway and over the Bagheera fountain, with a large branch that has rooted in the bed beyond and is cabled to its multi-stemmed main trunk. This tree, which may be over 150 years old, is in its decline, but the Friends work seeks to prolong its lifespan. To do so, we may need to reduce the weight of the wood in the crown, since it has significant interior rot and is vulnerable to wind damage because of its weakened wood. Click here to learn more about load reduction pruning in the Public Garden, Boston Common, and Commonwealth Avenue Mall.

One striking feature of ornamental Beech trees is their bark, which is characteristically smooth and light grey, like an elephant’s skin. Their beautiful bark is unfortunately threatened by two major concerns: vandalism by humans, and a suite of fungal diseases. The Friends of the Public Garden works tirelessly on both of these issues. Together with the Parks Department of the City of Boston, the Friends strives to maintain these parks at the highest level of excellence, to inspire the public to love and respect these important public resources (and refrain from vandalizing them!) And most significantly, the Friends hires hard-working professionals who use the latest scientific practices of Integrated Pest Management to treat the beeches for fungal bark diseases, such as the phythoptera canker and nectria.

Across from the Hampshire House and Cheers, one finds a grove of Beech trees, planted in the 1980’s by two significant early Friends of the Public Garden, Polly Wakefield and Westy Lovejoy. Both woman were long-term members of the Board and Horticulture Committee. This cluster of trees, a testament to these two volunteers’ many years of service, is thriving thanks to the careful pruning, disease management, and judicious fertilizing the Friends has provided over the decades. I like to imagine that in 150 years a new generation of park lovers will look up at the marcescent leaves and wonder when spring will ever arrive.

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Claire Corcoran is an ecologist and member of the Friends of the Public Garden Board of Directors. She is a self proclaimed “tree hugger” and dedicated advocate for greenspace in Boston and beyond. Claire lives in the South End of Boston with her husband and three children.

 

Photos by Claire Corcoran

Meet the Trees: Mighty Oaks

For November our Tree of the Month is the Oak, one of only a few local trees to be the last to lose its leaves.  Well into the winter season, Bostonians will be able to look up at shivering branches almost uncannily cloaked with tenacious brown oak leaves.

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Oaks are an astoundingly diverse group of trees – there are 600 species all over the world, and 90 species in North America. These mostly deciduous trees hybridize easily and are sometimes difficult to identify.  The wood of oaks, as well as their acorns, is high in a type of polyphenol called tannin—the source of its strength, resistance to rot and insects, and the flavor oak barrels can impart to their contents (well known to lovers of “buttery” chardonnay).

Here on the Boston Common and in the Public Garden, Pin Oaks, Red Oaks, and White Oaks are among the largest trees. The Commonwealth Avenue Mall has over 30 specimens and four species of oaks, the Garden over 20 specimens and seven species, and the Common over 50 specimens and five species.

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The tree fruit—mostly acorns—carpeting the forest floor this time of year is collectively called “mast”, from the same Old English word (“maest”) that gave us the word “meat.” Bumper acorn crop years are called “mast years” and are directly associated with huge fluctuations in wildlife populations, which can then have ripple effects on populations of other creatures like ticks that feed on oak-dependent wildlife such as mice and deer.

Early humans all over the globe ate acorns, after processing them in various ways (soaking, drying, etc). Until relatively recently in human history, acorns were a significant source of calories for humanity – by some estimates up to 10 percent.

When Europeans came to North America, the old growth oak forests here were an attractive natural resource, as oak was an important building material that had been mostly exhausted in Europe.  Oak was used in shipbuilding, quarter sawn for oak furniture, and prized for barreling wine and spirits.   The old-growth White Oak planks of the USS Constitution withstood so many English shells that the sailors nicknamed it “Old Ironsides.”

Oak forests still thrive in Southern New England, and are characterized by dry, sandy soils, other fire adapted plants such as blueberry bushes and various pine species, and hickory species.  On Cape Cod, Martha’s Vineyard, and Nantucket, the familiar low twisty maritime forests are also dominated by fire adapted oaks and their associated understory species and pollinators, some of which are rare and endangered species of moths and butterflies.

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In some parts of New England, oaks face a new kind of threat – overgrazing by deer.  Without many predators, deer populations have exploded in New England, and excessive browse of oak seedlings and saplings by deer is exerting pressure on successional change in the forested landscape.

As you walk through our three parks, look for urban wildlife feeding on acorns—squirrels are ubiquitous, of course, but you might also see crows, jays, ducks, geese, raccoons, opossums, and perhaps even foxes. Then take a moment to look up at the familiar lobed leaves that not so long ago shaded us on those hot summer days. We have so many reasons to feel grateful to the oak!

 

Forget to read last month’s tree, the Dawn Redwood? Read it here!

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Claire Corcoran is an ecologist and member of the Friends of the Public Garden Board of Directors. She is a self proclaimed “tree hugger” and dedicated advocate for greenspace in Boston and beyond. Claire lives in the South End of Boston with her husband and three children.

Meet the trees: Dawn Redwood

FOPG Dawn Redwood

The Dawn Redwood (Metasequoia glyptostroboides) is an Asiatic, deciduous conifer that has a storied past and deep Boston roots. This beautiful tree was well known to science from the fossil record – fossils had been found in North America, Asia, and Greenland– but was thought to be extinct. In 1943, a Chinese forester discovered a living specimen, and in 1946 Chinese scientists realized that it was the same plant as the fossil. In 1948, an expedition from the Arnold Arboretum of Harvard University collected seeds from the original tree, of which many ornamental Dawn Redwoods are descendants.

Dawn Redwoods grew widely in the Northern Hemisphere in the Mesozoic era, when dinosaurs dominated the fauna. They date back 100 million years in the fossil record, but are now restricted to several small stands in China. Classified as critically endangered by the International Union for Conservation of Nature (IUCN), the fast growing tree is now planted widely at botanic gardens and parks around the world.

Its pale green needles and ferny foliage turn pink and gold to brown in the fall before dropping off. Its conical growth form is distinctive, and it is often planted along waterways or in groves. The specimens in the Public Garden were likely planted in the 1950s.

How amazing that this ancient species, with help from humanity, has recolonized its Mesozoic range after being reduced to a single population!

FOPG_Claire_Corcoran_photo

Claire Corcoran is an ecologist and member of the Friends of the Public Garden Board of Directors. She is a self proclaimed “tree hugger” and dedicated advocate for greenspace in Boston and beyond. Claire lives in the South End of Boston with her husband and three children.