Winter Color at the Arnold Arboretum, Part 2


Arnold Arboretum


A few weeks ago, with the advent of the first significant snowfall in Boston, I wrote about the flashes of color and life I found among the laden bushes and boughs at the Arnold Arboretum. What a fantastic time for observing nature, after a fresh snowfall! Those who brave the frigid temperatures and ankle-deep drifts are rewarded with the sight of a transformed landscape, lit by a clear blue sky. Robert Frost described it lovingly in “A Winter Eden” (1923):

A winter Eden in an alder swamp
Where conies now come out to sun and romp,
As near a paradise as it can be
And not melt snow or start a dormant tree.
It lifts existence on a plane of snow
One level higher than the earth below,
One level nearer heaven overhead
And last year’s berries shining scarlet red.
It lifts a gaunt luxuriating beast
Where he can stretch and hold his highest feast
On some wild apple tree’s young tender bark,
What well may prove the years’ high girdle mark.
Pairing in all known paradises ends:
Here loveless birds now flock as winter friends,
Content with bud inspecting. They presume
To say which buds are leaf and which are bloom.
A feather hammer gives a double knock.
This Eden day is done at two o’clock.
An hour of winter day might seem too short
To make it worth life’s while to wake and sport.

Last week, after a second storm left six inches of heavy, wet snow, I decided to venture out at sunrise and see what I could find.


Turdus migratorius (American Robin) eating ilex berries


Against a subdued backdrop, the activity of birds and mammals is readily observable, as they tirelessly search for sustenance. This audacious male robin (Turdus migratorius) snacked happily on the fruit of the common winterberry (Ilex verticillata) as I watched from a few feet away. Berries are an important food source for robins, allowing them to survive much further north during winter than many migratory birds in North America. They are among the first birds to lay eggs each year, and are often considered a symbol of spring.


Chionanthus retusus (Chinese Fringetree) fruit


Many plant species, such as the Chinese fringetree (Chionanthus retusus), retain their berries through winter. As an ornamental transplant from Asia, I am unaware of any native animals using these berries as food.


Hamamelis mollis 'Princeton Gold' (Witch Hazel) winter flowers


Witch Hazel (Hamamelis mollis ‘Princeton Gold) is from a fascinating genus. Native to central and eastern China, this species blooms in late winter/early spring, while almost no other plants are flowering. Its flowers are delicate and bright, with narrow yellow petals, often turning red near the base. In this image, you can see dormant apical buds that will produce foliage in spring, along with woody brown capsules that hold the mature seeds from last year’s mast. These capsules will split explosively, launching two black seeds onto the ground below.


Liquidambar styraciflua (Sweet Gum) fruit


Sweetgum (Liquidambar styraciflua) is another species that retains much of its fruit through the winter. I found these seed pods hanging heavy with snow, accompanied by bright, fat flower buds. Sweetgum buds are colorful, showing shades of red, green and purple.


Fagus grandifolia (American Beech) Quercus rubrum (Red Oak) with snow-laden foliage


The beech leaves (Fagus grandifolia) and red oak sapling (Quercus rubra) above have retained their autumn leaves. During fall, through chemical means, spent leaves on deciduous species are typically released from branches in a process called abscission. The vascular connections between branches and petioles are sealed off, in preparation for winter. A few species retain these spent leaves, which will detach mechanically with the advent of new foliage in spring.

It is unclear whether this characteristic, called marcescence, is beneficial for the tree, or simply the result of the incomplete evolution of the standard deciduous leaf. Some have hypothesized that the bitter taste of senesced leaves protects buds and young shoots from foraging herbivores. It is clear that juvenile trees express this quality more often than mature trees. Whatever the cause, these retained leaves add flashes of warm color to the winter landscape.


Quercus rubrum (Red Oak) with fallen limb tumblr_o27e25iaaU1qdx0sdo1_1280


Marcescence can cause lots of trouble for trees during winter. As with the weary oak sapling above, snow-laden foliage can put tremendous stress on tree limbs and eventually cause them to fail. During my visit, I witnessed an impressive amount of damage done to deciduous trees and conifers alike, as can be seen above. These downed limbs easily weight hundreds of pounds and are incredibly dangerous (not to mention a significant burden to groundskeepers). Needless to say, I was cautious about where I chose to explore during my walk.


Snow-laden evergreen Snow-laden trunks Snow-laden evergreens


Conifers are better adapted to alpine conditions than deciduous trees. Triangular profiles reduce wind resistance and prevent the accumulation of heavy snow on upper branches. The size and shape of needle-type foliage prevents damage from blowing wind and snow. These adaptations help mitigate the venerability caused by the shallow root systems often found on conifers, which can lead to poorly-anchored specimens blowing over.

It’s easy to see from the images above that wet, heavy snow is a huge liability for trees. Fortunately, the supple young wood of these trees offers a great degree of resistance to breakage.


Animal prints under spruce


Snowy conifers present other dangers as well. During heavy storms, protected spaces around trunks often form large voids called tree wells, where no snow accumulates. Hikers or skiers who accidentally fall into these pits run the risk of bringing down more snow from overhead boughs as they struggle to free themselves. Constant vigilance is the best defense while exploring in winter.

On a more positive note, the sheltered space under a conifer also makes a great hiding place for snacks! I found of evidence of a flurry of activity under this spruce. Something had dug through the snow and into the needle duff in search of food it had hidden. Both eastern chipmunks (Tamias striatus) and eastern gray squirrels (Sciurus carolinensis) bury food for harsh winter months. Squirrels remain active throughout winter, while chipmunks go through periods of decreased metabolic activity called torpor. Both rely on caches of food during the winter months.


Birds prints Lepus americanus (Snowshoe Hare) prints


I also found prints left by birds (top) and a rabbit (bottom), most likely an eastern cottontail (Sylvilagus floridanus), which seem particularly abundant around the Arboretum.


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I’m always on the lookout for interesting and colorful winter buds, which contrast spectacularly with the snow. Clockwise from top-right: anise leaf magnolia (Magnolia salicifolia), American beech (Fagus grandifolia), Manchu striped maple (Acer tegmentosum), Szechuan Filbert (Corylus heterophylla var. sutchuenensis).


Arnold Arboretum winter landscape


By noon, the Arboretum was filled with people cross-country skiing, hiking and admiring the snow. After last year’s record-breaking winter, I thought I’d never want to see another snowflake, but all things considered, it was a fantastic day of exploring in the wintry New England landscape.
Thanks for reading,

Dan

 

A few more photos from the day:

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