Tag Archives: Plants

How to answer an ogre: or lessons you should have learned in 8th grade science

The tree looks like a petrified ogre caught in the act of eating chains. Like an ogre who might guard a bridge and when you try to pass asks you a math problem in a voice that sounds like he’s gargling gravel. If you answer correctly you will hear him say, “You may pass.” Get it wrong and you’ll hear your bones crunch in his chain-eating jaws.

You pound a nail into a tree three feet off the ground. If the tree grows 1.79 feet per year, how high up will the nail be in 4 years and 36 days (0.008 years)?

You have one minute to solve it.

The answer is three feet. Did you find yourself in the ogre’s mouth on the other side of the bridge?

Ogre tree chomps on chains, Williamsburg, VA (4)

The ogre was testing your 8th grade science knowledge. The reason the nail stays at the same height is because trees add layers at the top, not at the bottom. A tree grows taller from the apical meristem at the tips of branches and trunks. Roots elongate the same way, they add tissue at their tips. This is why a barbed wire fence nailed to a tree thirty years ago isn’t 20 feet in the air today. Or why those initials you and your wife carved into that oak tree saying you’ll be together forever in 1998 is still at eye level and why you now have to walk your new wife hurriedly past that tree hoping she doesn’t notice. But wait long enough and maybe the lateral meristem will cover your shame.

Trees grow taller from the tips and fatter from the outer layers. Stem and trunk diameters increase each year as a new layer of wood is wrapped around the tree. This is why – after a while – a tree looks like its chewing on barbed wire or old dog chain left behind by former tenants. The barbed wire stayed in place as the new layers grew past it.

Ogre tree chomps on chains, Williamsburg, VA (2)

The Mountain 2013 (61)
Nom, nom, nom.
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The winter sculptress

January 2015, Eastern Virginia

Ice covered marsh elder - Yorktown, VA, Jan 2015 (1)

The icy fog of winter swallows the Mid-Atlantic. The temperatures drop below freezing and weld the fog to all that it touches. Everything – limbs, leaves, porch steps, 1999 Honda Civics – are glazed with an 1/8 inch rime. Were I snail and one who could skate, I would don my snail sweater and skate (having only the one foot) and invite all my snail-skating gastropod-friends to my front steps and glide from one rail to another. Limbs sag heavy under the new weight. I – not wanting to skate on my steps – grab the rail. It too is slick with the icy slobber of a winter fog – and hold both my breath and myself as best I can. Winter redeems itself as an artist – the world now a garden of ice sculptures.

I scrape ice from my windshield with an bottle because apparently owning an ice scraper is much too much of a luxury. THe holes I make in the ice likely are not street legal as most of my view still obscured, but I take my chances and drive of to admire winter’s artistry.

Ice covered marsh elder - Yorktown, VA, Jan 2015 (3)

Of course I stop in the marsh. That is what you do when every surface you touch is lacquered with ice. Here in Virginia the Spartina stems – though dulled and browned with age – still stand. Today they glisten. Each leaf, each stem encased in a crystalline sheath. One that is cracked like, but intact. Like a mosaic of glass pebbles – each magnifying the beauty of which it clings. On the bushy marsh elder, each leaf is a glassy pendant.

Ice-covered Spartina - Yorktown, VA, Jan 2015 (2)

Ice covered marsh elder - Yorktown, VA, Jan 2015 (3)

My hands, without any sheath – glove or ice or otherwise – beg me back to the car. From the comfort of a defroster I admire what is now an icy meadow of marsh. By the weekend, the 50 degree temperatures will strip away the artistry of winter, each glassy sculpture losing its luster yielding to the rough concrete texture of winter’s true self.

Marcescence – the art of not letting go

I think this is the alpine hairy cap moss, Polytrichastrum alpinum
I think this is the alpine hairy cap moss, Polytrichastrum alpinum

I was in Denmark, Maine, this weekend doing very Maine things. Shoving sclerotized sunshine (wood) into the belly of an iron wood stove. Walking alongside a mountain brook with moss-covered rocks licked with a verglas (ver-glaze) of ice. The verglas an art of steely-eyed primeval monsters frozen in time or a hundred fingers overlapping each other to grip the rock. For a time the ice held my imagination as it held the rocks.

I, for the first time in my life, enjoyed a superheated sauna. And once my body reached the right temperature, a local convinced me to jump in an icy brook. The mercurial abuse I gave my body made me superhuman. It detoxified my spirit and I bravely walked in the nighttime air shirtless, immune to deep fall’s icy breath. It was the crunch of snow under my tender feet that reminded me that I was a mortal.

Absorbing the painful joy of steep hikes on a snow-dusted mountain, I took in the tinkling spread of sunshine of moss that held tiny bits of ice, like tinsel on a tree. It was the American beech (Fagus grandifolia), however, that drew most of my attention. On its branches were papery brown leaves – leaves that will loiter on the branches all winter unlike the rest of the foliage that was now underfoot. Marcescence is the term for deciduous trees that do not shed their leaves though they’ve lost their color. Throughout the mountainside was a forest of leaves that refused to fall despite the namesake of the season.

American Beech, Fagus grandifolia, Denmark, Maine (1)

The American beech. Onto its leaves it holds.
The American beech. Onto its leaves it holds.

The hypotheses about why a tree may keep its leaves throughout the winter range from deterring the nibbling deer to preserving its nutrients. I am too lazy to do the research on the science of marcescence. Fortunately, my good friend David Haskell (another great wordsmith scientist) has done that work already.

I have my own marcescence, hanging onto things that I should have long ago shed. In my closet loiters a pair of jeans that I won’t wear because they are more holes than jeans, but keep because they are extremely comfortable. I say I will fix them one day. No. No, I won’t. I should dispose of these vagrants.

My mind holds onto memories that I don’t need. From worthless minutiae about the fact that I had only one egg with my pancake last Wednesday (I only had two eggs left and I broke one of them trying to flip it for over-easy and I threw it away frustrated – why do I need that taking up space in my brain?) to painful memories of anger. Of recriminations. Of hurt and of heartache.

And it is my heart that is the guiltiest of marsescence. I have lingered too long in relationships where we enjoyed a hopeful spring that erupted into a frenzied summer that then reached a fall withering. In the winters of those relationships I have held onto the leafy reminders of those summery days, hopeful of their return when I should have let those dead leaves drop.

It is not yet clear why the leaves of the beech do not drop. Maybe the beech is like me. It simply cannot let go.

Pickleweed

Saltmarsh Pickleweed, Salicornia europaea, in fall colors in Rowley, Massachusetts
Saltmarsh Pickleweed, Salicornia europaea, in fall colors at high tide in Rowley, Massachusetts

The week of 21 September 2013
Rowley, Massachusetts
I step onto the marsh and it announces autumn.  Before the leaves of the trees are set afire with an autumnal blaze, before the morning air is tart with a cold bite, scarlet forests of pickleweed are the first to foretell fall’s approach.  

I’m standing in the middle of a scarlet forest that extends for meters in either direction but stops abruptly against the taller Spartina alterniflora.  Among the golden buttery straw of Spartina I see small flare-ups of scarlet picklweed here and there.  The haphazardness of these patches is interesting in this salt marsh, because it has strict patterns of vegetation governed by the tides and competition among species.  The scarlet adds a color mosaic to an otherwise monotone palette.  The randomness of color is inspired by the gypsy lifestyle that the pickleweed has adopted.  It is a gypsy of populations, not necessarily individuals.  Individuals have one season to grow, reproduce, and die, making them annual plants (vs. perennials which persist for more than one year).  Its shallow root system and short stature (~20 cm) make it a weak competitor, thus it must be able to move on a whim as a population if overrun by superior competitors.  To survive on the marsh the pickleweeds must be opportunistic.  It is often found in areas where vegetation has been killed by disturbance or stress.  This most often happens when wrack – mats of dead vegetation that are carried by the tides – lays on top of living vegetation and smothers it.  The vegetation dies and the wrack is carried off by a spring tide (maybe weeks or months later), leaving behind a bare spot in the marsh.  For years, large swaths of wrack sat on this marsh, pushed against the levee that is the road by winds and tides, and smothered the marsh.  Some of the wrack is now gone and within a season half of the bare patch is colonized by picklweed.  This large stand of pickleweed may hold this spot for two years or more, until it is evicted by the deep-rooted and tall Spartinas that march across the marshscape.  The dots of pickleweed in the marsh are plants that squeezed in between Spartina neighbors where the canopy thinned and opened up, probably due to salt or flooding stress.  These gypsies are not picky where they settle; they know they won’t be there for long.

Wrack smothering marsh grass. As the tide lifts it off, it will leave behind a bare spot.
Wrack smothering marsh grass. As the tide lifts it off, it will leave behind a bare spot.

On another marsh, the foot of the scientist is the disturbance.  Each year a path is established to get to sampling locations and each year the path is moved to minimize footfall impact.  Now this year’s bare path runs parallel to line of scarlet as the pickleweed have occupied last year’s path.

This year's footpath paralleled by last year's, which is occupied by a line of scarlet pickleweed. This year’s footpath paralleled by last year’s, which is occupied by a line of scarlet pickleweed.

I kneel down and squeeze a fleshy finger of pickleweed.  It’s succulent. Succulence is a strategy used by plants to deal with low soil-water potential, that is, it’s hard to get the water out of the soil.  This happens in habitats where the soil water has a high salt concentration when there is infrequent rain (deserts; think cacti) or inundation by salty water (salt marshes and mangroves).  To increase the plant’s water potential (i.e., the potential of water moving into the plants) it increases osmotic pressure in its favor by storing salts in its cells.  This makes the plant saltier than the soil.  As we know with osmosis, water moves from areas of low salt concentration to high salt concentrations.** During a visit to the marshes of Barn Island, Connecticut , my friend Dr. Scott Warren demonstrated the plant’s osmotic strategy.  He squeezed the juice from a pickleweed onto a refractometer.  90 parts per thousand (ppt)!  Almost 10% salt!****  He pulled out a pocket knife, cut out a bit of marsh turf and squeeze it onto the refractometer.  55 ppt!  Aha!  So now the plant is able to pump water from the soil to plant passively via osmosis!  For reference, marine salt water is ~32-35 ppt.   

A forest of pickleweed
A forest of pickleweed

High salt concentration can disrupt cell function and kill you.  Here again, the gypsies are clever to prevent a briny death.  One feature that defines a plant as a plant is the presence of a large central vacuole in the cell.  These vacuoles are like large storage trunks separated from the cytoplasm and other organelles by a plasma membrane.  Plants shove all kinds of things into these cellular trunks and pickleweed stuffs its vacuole with sodium ions.  The cell is protected because the salts are safely stuffed into the salty trunk.

It is the saltiness of these cellular trunks that I am currently drawn to now.  I pluck a scarlet finger of pickleweed I bite into it.  It is soft, but firm and gives a slight crunch, which is why it’s sometimes called ‘glasswort’.  It’s salty but nothing that excites my taste buds.  Locals tell me people eat on salads but I’ll be damned if I’ve met anyone who has actually done that.  The wise internet tells me it is sometimes pickled in Great Britain (perhaps where the name ‘pickleweed’ comes from?). 

But tell me pickleweed, why the red?  You’ve abandoned your green because you’re breaking down the sun-harvesting chlorophyll as you begin to senesce.  You are winterizing.  But why the reds?  The reds come from your production of a class of pigments called anthocyanins, which come at an energetic cost.  Why spend the energy to make these pigments when you’re nearly dead?  Maybe you are signaling to grazers – perhaps a hungry salad-eater who needs a salty crunch –  that you should be eaten so that your seeds can be carried away?   

The pickleweed gives me no clues to this mystery.  Perhaps one of you out there know better.  

I pluck another red finger, which has many joints called nodes, and break the finger at one of those nodes.  It snaps and reveals two white circles.  Seeds.  The plant will soon loose it’s succulence, desiccate and release its seeds.  The seeds are the true gypsy form and they will caravan on the tides until they find their own one inch of marsh soil to call home next year.

**This is why you can kill a snail with salt; the water from the snail’s body exits its body wall to the saltier environment.  I can’t believe you did this you heartless bastard.  Didn’t you even hear him scream?

****I originally reported this at “almost 1% salt!” because I apparently can’t do math.