Archive for the 'Trees' Category

Jan 05 2014

Two Resins For Tomorrow

Published by under Musings & News,Trees

Frankincense from Yemen (photo from Wikimedia Commons)

Back in December when I wrote about amber, I learned about other tree resins important to humans.  Two of them are celebrated tomorrow on the traditional anniversary of the visit of the Magi who brought gold, frankincense and myrrh to the infant Jesus.

Frankincense, native to the Arabian peninsula and the Horn of Africa, is a hardened resin used in religious ceremonies around the world. It’s been traded for at least 5,000 years, burned as incense or steamed to release its essential oils.

The resin is produced by slashing the bark of trees in the Boswellia genus as often as two to three times a year.  Some say that Boswellia sacra produces the best.  Ironically frankincense trees are declining because agricultural pressure is clearing the land and the remaining trees can’t produce viable seeds if they’re slashed too often.

Frankincense tree, Boswellia sacra (photo from Wikimedia Commons)

 

Myrrh is the resin of thorny trees in the Commiphora genus, valued for its religious and medicinal uses.  Just like frankincense it’s produced by slashing the tree’s bark to make it ooze sap.

Myrrh (photo from Wikimedia Commons)

Commiphora myrrha is one of the species favored for myrrh and because it is native to Yemen, Somalia, Eritrea, and eastern Ethiopia Biblical scholars say that the wise man who gave that gift came from one of those countries.

Commiphora myrrha produces myrrh (image from Wikimedia Commons)

 

Tomorrow these two resins will be in the limelight, though frankincense and myrrh are used throughout the year.

 

(photos from Wikimedia Commons. Click on the images to see the originals)

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Dec 26 2013

Tiny Mistletoe

Published by under Plants,Trees

Dwarf mistletoe, Arceuthobium americanum, female plant (photo by John W. Schwandt, USDA Forest Service, Bugwood.org)

‘Tis the season for kissing under the mistletoe but this genus is too small for the purpose.

Mistletoes are parasitic plants in the sandalwood family.  The ones we associate with kissing, Phoradendron leucarpum and Viscum album, are evergreen plants that parasitize oak and apple trees.  In winter they look like green balls in the bare trees.  Click here for a photo and description.

Dwarf mistletoe, on the other hand, is amazingly small.  Arceuthobium’s 42 dioecious species parasitize only conifers.  The female plant of American dwarf mistletoe (Arceuthobium americanum) is shown above, the male below. Notice the tiny size of the plant relative to the pine needles.

Dwarf mistletoe, Arceuthobium americanum, male plant (photo by Brytten Steed, USDA Forest Service, Bugwood.org)

Dwarf mistletoe begins its life as a seed that lands on a tree branch, then germinates and grows beneath the bark, sucking water and minerals.  It rarely kills the tree but the tree fights back by developing witches’ brooms or losing branches as shown on this lodgepole pine.  Foresters hate dwarf misletoe.

Dwarf mistletoe, Arceuthobium americanum, damage to lodgepole pine (photo by Mike Schomaker, Colorado State Forest Service, Bugwood.org)

 

Many mistletoes depend on birds to spread their seeds, but dwarf mistletoe takes matters into its own hands.  During the 18 months of seed maturation, water pressure builds up in the seed capsule until it finally bursts out, traveling at almost 50 mph … like this!

Dwarf mistletoe, Arceuthobium americanum, shoots a seed (photo by Frank Hawksworth, USDA Forest Service, Bugwood.org)

Pow!  The size of a grain of rice, it can travel 65 feet!

Tiny but powerful.  Watch out below!

 

(all photos are American dwarf mistletoe, Arceuthobium americanum, from Bugwood.org: 1241494 by John W. Schwandt USDA Forest Service, 2141082 by Brytten Steed USDA Forest Service, 2250003 by Frank Hawksworth USDA Forest Service, 5367211 by Mike Schomaker Colorado State Forest Service)

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Dec 24 2013

Norwegian Gifts

Published by under Books & Events,Trees

Norway spruces (photo from Wikimedia Commons)

When you see a tall evergreen with drooping branches in eastern North America, chances are it’s a Norway spruce.

Native to Europe, Picea abies is cultivated widely for landscaping and is now naturalized from Connecticut to Michigan.  Elsewhere the trees must be planted but they do quite well, tolerating more heat and humidity than other conifers.

Norway spruces are easy to identify because their drooping branches resemble the fringed sleeves on a cowboy jacket and their cones are long and thin with papery scales.

Norway spruce cones (photo by Randi Hausken, Creative Commons license on Flickr)

In Germany this species became the first Christmas tree.  In fact, it’s the tree that adorns New York’s Rockefeller Center, London’s Trafalgar Square, Edinburgh’s town square and Washington DC’s Union Square right now.

Every year since 1947 the City of Oslo has given a Norway spruce as a Christmas tree to those four cities in gratitude for U.S. and U.K. help during World War II.

Here’s Rockefeller Center’s tree on the 40th anniversary, Christmas Eve 1987.

Christmas tree,Rockefeller Center, 1987, gift of Oslo, Norway (photo from Wikimedia Commons)

Click on the city names above to read about these beautiful Norwegian gifts.

 

(photos of spruce and Christmas tree from Wikimedia Commons. photo of cones by Randi Hausken, Creative Commons license on Flickr. Click on the images to see their originals)

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Nov 30 2013

Late November Signs Of Life

Witch hazel blooming in Schenley Park, 28 Nov 2013 (photo by Kate St. John)

Though it’s been cold and snowy I found signs of life in Schenley Park on Thanksgiving Day.

Above, witch hazel is blooming along the Lower Trail.  The yellow flowers don’t stand out but once you notice them you’ll see several trees sporting lemon-peel petals.

Below, bush honeysuckle stands out green against the snow.  This out of synch condition reminds us that this plant is from another country.

nvasive plant out of sync with our seasons (photo by Kate St. John)

When you see green deciduous plants in the snow, check them out.  They’re often imports.

 

(photos by Kate St. John)

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Nov 20 2013

The Branches Add Up

Published by under Trees

Bare tree at sunset, Philadelphia (photo from Wikimedia Commons)

Now that the trees are bare you can do a little math on their branches.

Did you know that if you start at the trunk, gathering together all the branches and squeezing them tightly all the way to the top, the bundled branches will be the same circumference as the tree trunk?  The tree would be one big cylinder, all the same thickness as the trunk.

This principle is Da Vinci’s Rule of Trees. More than 500 years ago Leonardo wrote: “All the branches of a tree at every stage of its height when put together are equal in thickness to the trunk.”

Intuitively we can guess this is true, but the rule is very impractical to prove by hand.  A small tree could be squeezed – and sacrificed by the experiment – but a larger tree has to be measured and calculated.  As physicist Christophe Eloy of University of Provence said, “If you’re looking at big trees, there’s thousands of branches, and it takes a lot of undergrads to measure it.”

Two years ago Christophe Eloy proved Da Vinci’s Rule of Trees and the reason why it occurs by designing intricately branched trees on a computer and putting them through a virtual wind tunnel.

The designs, like the trees, were branching fractals repeated over and over.  With each design Eloy varied the thickness of the branches and subjected them to virtual wind forces that broke them.  Invariably when he found a combination that withstood the wind, it matched Da Vinci’s rule.  This not only proved the rule but showed that wind is a reason for the rule’s existence.  His findings were published in the journal Physical Review Letters in 2011.

Of course Eloy’s proof involved math and physics.  Here’s his diagram of the fractal thickness and one of his computed trees.

Tree branches and trunks follow Da Vinci's Rule (image courtesy Christophe Eloy, University of Provence)

(Image Courtesy Christophe Eloy | University of Provence)

 

But don’t take my word for it.  Read more about Christophe Eloy’s study and Da Vinci’s Rule of Trees at this link in Inside Science.

 

(photo of a bare tree at sunset from Wikimedia Commons.  Tree diagram courtesy Christophe Eloy, University of Provence linked from Inside Science.  Click on each image to see its original.)

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Nov 10 2013

Face In A Gall

Oak apple gall that looks like a face (photo by Kate St. John)

Before the oaks leafed out last spring I found this oak apple gall on a seedling at Cedar Creek Park.

When I bent down to look closely I saw the face.

Now that the leaves have fallen, look for fun features like this on the bare trees.

 

(photo by Kate St. John)

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Oct 27 2013

Wild Hickory Nuts

Shagbark hickory nuts (photo by Kate St. John)

Here’s something I literally stumbled on in Schenley Park:  shagbark hickory nuts (Carya ovata).

The big round balls, which cradle easily in the palm of my hand, are husk-covered nuts.  They’re green when ripe but turn brown with age (bottom right).  Their four sections naturally come open as the nut ages and sometimes burst when they hit the ground.

I didn’t need any special tools to open the husks, just my fingers.  At first I didn’t realize they were merely husks so I thought it was odd that they didn’t protect the nut but…

The nutshell is another story (center of the photo).  Irregularly shaped and slightly larger than a quarter, I tried to open it by cutting and other gentle means but it was impossible.  The meat inside is reputed to be sweet but I had to destroy the nut to taste it.

Hmmm.  Get out a hammer or hire a squirrel.

I got out the hammer.

The first nut had very shriveled meat inside.  Perhaps it had been attacked by a bug.

The second and third nuts looked promising except that the meats resembled dried Chinese wood ear mushrooms and they tasted like nothing.  (My photo doesn’t do this justice.)

Shagbark hickory nuts, hammered open (photo by Kate St. John)

Either I was doing something wrong — quite possible — or these nuts are not as good as described.

I wonder how many nuts the squirrels spend time opening only to find that the meat inside was not worth it.

(photo by Kate St. John)

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Oct 26 2013

Twisted Trunks

Black cherry and red oak twist around each other, Moraine State Park, Oct 2013 (photo by Kate St. John)

Last weekend I found these twisted trees in Moraine State Park.

It’s unusual to find trees like this — even more unusual when they’re two different species.

A black cherry (left at base) and a red oak (right at base) germinated next to each other.  At the ground their trunks touched and melded. As they grew they twisted around each other.

Amazing.

(photo by Kate St. John)

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Oct 25 2013

An Alien Takes Aim At Old Treasures

Hemlock woolly adelgid at Jacobsburg (photo by Nicholas A, Tonelli via Wikimedia Commons)

Last spring the hemlock woolly adelgid (HWA) reached Cooks Forest, scary news for the old-growth eastern hemlocks there.

The pest is easy to recognize by its white egg sacs that cling to the underside of the branches.  They kill hemlocks by sucking the juice out of the needles.  Infected trees look gray-green instead of deep green and, under a heavy infestation like the one shown above, can die in only four years.  This is sad anywhere but especially unfortunate in Cooks Forest where the old growth hemlocks are over 300 years old.

It has taken a long time for the bug to reach Cooks Forest.  HWA arrived from Asia in 1924 but moved very slowly across the eastern U.S.  By 2007 it was present in 50% of the eastern hemlock’s range, unable to spread far northward because of harsh winters. Unfortunately our climate is warming so new adelgid territory opens up every year. (Notice on this NOAA plant hardiness map that the location of Cooks Forest warmed enough to change growing zones.)

HWA was first spotted in eastern Pennsylvania in 1967 but took about four decades to cross the Allegheny Front into western PA.  Slowly, slowly it crept toward Cooks Forest.  By 2010 it was in the vicinity.  This year it was there.

Knowing the imminent danger DCNR has treated the area and the old growth trees.  They use biological controls — Asian beetles that eat adelgids, though not enough of them — and soil or bole-injected insecticides on specific trees.  The poisons are systemic, similar in concept to the insecticide treatments for emerald ash borer that kill or repel all insects.  The treated trees will have fewer insects living on them.  Will this make them less useful to birds?

The question hardly matters.  Nature can’t produce a 300 year old hemlock as fast as the adelgids can destroy one.   In the case of our oldest treasures our task is clear.  Save these trees if we can.

For more information on the hemlock woolly adelgid, click here for DCNR’s report.

 

(photo via Wikimedia Commons by Nicholas A. Tonelli at Jacobsburg, Northampton County, PA. Click on the image to see the original)

 

p.s. Thanks to Kim Getz for alerting me to this news.  Because of the adelgids activity cycle, DCNR treated the old-growth trees in May and again in October.

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Oct 13 2013

Tree On Stilts

Published by under Trees

Tree on stilts, Parker Dam State Park, October 2012 (photo by Kate St. John)

During a hike at Parker Dam State Park last year I noticed this hemlock, a tree on stilts.

Hemlocks have shallow root systems and can sprout easily in moist locations.  Sometimes they sprout in the moss on top of a rock or stump and their roots follow the contour across the surface and become anchored in the earth nearby.

My guess is that this tree sprouted on a stump that decayed out from under it.  The support disappeared after the hemlock’s root system was already established but the hemlock didn’t care.  It sent down some new roots and just kept growing in place.

Hemlocks in this position are vulnerable in wind storms but this one is in the understory, surrounded and protected by many other trees.

It will probably surprise hikers on the Beaver Dam Trail for a long time to come.

(photo by Kate St. John)

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