50 Shades of Brown

Yes, yes, that title is a reference to the 2011 erotic romance novel “Fifty Shades of Grey,” which went on to spawn four more books, three movies, two song albums, a parody movie (“Fifty Shades of Black”), and a guest appearance as a book club selection in the movie “Book Club.” But enough for a belabored frame of reference – this column will have no sex scenes, no sadism, no masochism, no bondage, no dominance, no submission. Instead, it has leaves. Lot of leaves. In winter.

As to why leaves turn brown, that is more of colors departing than brown being added. Spring to summer to fall, each leaf is in a dynamic state. Leaves are an energy factory, continually synthesizing more chlorophyll so as to convert sunlight to sugar. Toward the end of our temperate zone growing season, as days shorten, chlorophyll synthesis stops. Green fades. In school, we might have been taught that the yellows and oranges and reds and purples of fall leaf color were always present, only becoming visible with the loss of green. Current thinking is more complex. Plants need time to withdraw sugars and carbohydrates from leaves, to be stored in roots over winter. More of the color compounds – anthocyanins – are made in leaves to protect against ultraviolet damage, i.e., sunburn, while nutrients are being salvaged.      

Another part of the leaf life cycle is “abscission,” the means by which leaves fall from trees. At the time of each leaf’s creation there is a specialized layer of cells where the leaf stalk joins the stem – the abscission layer. As days shorten, a tree hormone, auxin, decreases. This triggers a structural weakening on the abscission layer. Leaves are blown off by wind, or even on a quiet morning, can detach by their own weight. A branch broken in summer will have leaves that go straight to brown without intervening color, and the leaves will stay attached into winter.

Oak leaves on a fallen tree that turned brown 
but did not fall off. Click to enlarge photo.

There are a few species of trees that hang onto their brown leaves all winter: American beech and some of the oaks. Preternaturally retaining leaves in winter is called marcescence. As to why it happens, one theory is that beech trees do this, especially on young trees and lower branches of older trees, to discourage deer from feeding on the tree’s twigs and buds, which are a high-protein food source. Another theory is that not dropping winter leaves until spring serves to self-mulch the trees against competing plants trying to get started close to the tree trunk.

Back to brown. The major constituents of winter’s brown leaves are cellulose, hemicellulose, lignin, pectin, tannins and mineral content. The percentages of each dictate leaf shade from the pale brown of beech to the rich, dark brown of oak. Falling in between are ash, poplar, maple, birch, pine, hemlock and the various understory plants. Looking downward when out for a woods walk will reward you with myriad shades of brown.   

Winterberry berries, on ice

There are also accents of winter red. When berries go from green to ripe colors, the term is “veraison.” Same for grapes and many types of fruit. Two competing theories here – either these fruits are synthesizing polyphenolic compounds, which just happen to be colorful, to combat fungus growth, or the plants are signaling to animals that the fruits are ripe, and therefore OK to eat. Thinking for the latter concept is that by enclosing seeds in edible fruits, the plants are borrowing the animals’ digestive tract and wandering lifestyle to disperse seeds far farther than just falling to the ground. There is a name for this: “endozoochory.” Mammals and birds are the majority of seed-spreading participants, although plant-eating reptiles such as turtles can be involved.

The red we spy on winter walks included rosehips on Multiflora rose and berries on Burning bush, Japanese barberry, Oriental bittersweet and Winterberry. That is four invasive species and a native, respectively. Several bird species and small mammals will eat the rosehips, burning bush, and barberry, but the bittersweet and winterberry stay around until found by robins, either those who decided to not migrate or the north-migrating birds of spring. With the exception of barberry, none are considered people-edible, but rather mildly poisonous.        

European barberry is used to make jam. In Persian cuisine, barberry is “zereshk”, and “zereshk polow” is a traditional barberry and rice dish. While Japanese barberries are considered edible, strong reasons to why not bother to collect any include a need to separate fruit from seeds, nasty thorns, and the plants being a preferred habitat for deer ticks.  

 

The First Robin of Spring Isn't

Robins, winterberry, snow

Robins don’t leave anymore. American robins are omnivores, consuming fruit, berries, earthworms, and insects. They used to leave – their Latinate name Turdus migratorius says exactly that – and then come back in the spring. The “Turdus” part refers to being of the thrush family.  Emily Dickinson’s poem “I dreaded that first robin so” started with robins and went on to list other Spring-signs she dreaded such as daffodils and bees. And actually, they still do leave, mostly, but enough stay to make robin sightings year-round not particularly newsworthy. The reasons for seeing robins year-round is probably a combination of in part global warming and part a better winter food supply. A good resource for shifting bird territories is The Great Backyard Bird Count (www.birdsource.org). The next scheduled count is February 12-15, 2021.

Robins that leave New England spend the winter months in the southern states along the Gulf of Mexico or in central Mexico. Coming back, the male show up first. They travel 50 to 200 miles a day, staying behind the northward advancing line of temperatures above 37° degrees. That temperature is when earthworms will start appearing on the surface and also when the ground softens enough for female robins to collect mud with their beaks for nest building.

Spring sightings here in New England will be a combination of flocks stopping off temporarily but heading further north, and those that have stopped here, declared territories (the males) and started nest building (the females). If you hear a robin singing it is a local male declaring his territory.

In passing, “robin egg blue” as a color is defined as a shade of cyan (greenish-blue color) approximating the shade of the eggs laid by the American robin. Tiffany Blue is a trademarked name and trademark-protected version of robin egg blue uniquely associated with Tiffany & Co., a New York City based jewelry company. The company began using the color in 1845, not many years after its founding in 1837.

Robin, winterberry, snow

The robins that don’t leave, more males than females, gather in flocks of 20-50, sometimes co-mingling with wintering flocks of starlings. These are not the plump and gentle birds of summer with the hop-hop-hop-stop method of working a lawn for worms and grubs. In winter, robins are noisy and combative, working their way though berry bushes with the remembered aggressiveness of Bostonians at a Filene’s bargain basement sale.

Robins like winterberry berries (as do Cedar waxwings), but will eat just about any type of berry or fruit. One reason they may find New England more winter-friendly now compared to years ago is the prevalence of two invasive plant species: Oriental bittersweet and multiflora rose. Both the tree-topping vines and the arching ground brambles are lush with red berries by late-November. Many bird species will eat the multiflora rose berries, but the bittersweet crop is left for robins an waxwings

And why the name “robin?” When the English colonists started arriving in the 1630’s they named the local bird “robin” because its appearance reminded them of the European Robin. The species are not related. The European bird is smaller and has a red/orange face and bib, but a whitish belly. It is the national bird of the United Kingdom. When the English got to Australia the local red-breasted birds also became named robins. These “Flame robins” look a bit like our birds, only brighter. Unlike our species, the females lack the red breast color.

“Little Robin Redbreast” is an English language nursery rhyme. It goes, “Little Robin Redbreast, Sat upon a rail; Niddle noble went his head, Widdle waggle went his tail.” Earlier versions, dating to the 1700s, revealed a more coarse humor, to wit: “Little Robin Red breast, Sitting on a pole, Nidde, Noddle, went his head, And poop went his hole.”

There was an Atlantic Ocean crossing important to American robins. The common earthworms we see robins tugging from the earth and feeding to their chicks came over with the colonists. Although there were many species of worms native to the Americas, these immigrants are more adept at managing the colder climate of the northeast. Back across the ocean, earthworms are being threatened by another invasive species: the New Zealand flatworm. In parts of Scotland and Ireland native earthworms are now scarce – and the fertility of the soil is declining.

This is an expanded repeat of a column first published in December 2009.