Category Archives: Trees

Schenley’s Oak Wilt Trees Are Coming Down

Schenley Park, Trees

Oak stump upended to prevent the spread of oak wilt (Joseph O'Brien, USDA Forest Service, Bugwood.org)

Don’t be surprised when you see trees being felled this month at Prospect Drive in Schenley Park.  An acre of diseased trees must be clear-cut to protect the park’s healthy oaks.

Councilman Corey O’Connor held an informational meeting last night where we learned about the project from City Forester Lisa Ceoffe and Pittsburgh Parks Conservancy’s Erin Copeland.  They described oak wilt, its treatment, and the affected area in Schenley Park which I’ve drawn on the tiny map below.  Click on the map for a better view in Google.

Location of the Oak Wilt zone in Schenley Park, February 2014 (screenshot of shared Google map)

Here are some of the 55-60 trees that will come down, marked with blue logging paint last summer. Many of them are 100 years old.
Oak wilt trees marked for removal from Schenley Pak (photo by Kate St. John)

Why is the area so large and why must it be clear cut?

Oak wilt is caused by a fungus that doesn’t spread easily but can kill a tree in 30 days.  The fungus travels in the oak’s vascular system and when the tree detects it it blocks those vessels — the arboreal equivalent of a stroke.  Watch the 13 minute video here to see how this happens.  You know the oaks are sick when you see browning leaves in mid-summer.  This is the only sign.

Oak leaves showing oak wilt (Joseph O'Brien, USDA Forest Service, Bugwood.org)

The infection travels through an entire stand because the oaks are joined underground.  When their roots touch, they graft to share nutrients and, sadly, disease.  We only see the symptoms in summer so a large area can become infected before anyone notices.

Oak root graft (photo by Ronald F. Billings, Texas Forest Service, Bugwood.org)

 

Once the fungus has taken hold, an infected tree is doomed.  The only way to save nearby healthy trees is to trench the perimeter of the infection(*) and remove all the trees inside the circle.  Sap beetles can carry the infection so the logging must be done in winter when the sap isn’t running.  (Note!  Don’t prune your oaks in spring and summer.  This opens them to oak wilt.)

When the logging begins in about 10 days, Prospect Drive will be closed each morning when the equipment arrives and reopened when Davey Tree is done for the day.  Signs will be posted explaining what’s going on and Davey Tree will have brochures for those who want to know more.  The site is easily visible from the Boulevard so the City expects a lot of questions.  Now that you know what’s going on, spread the word.

By the end of February the area will be empty, but not for long.  Site restoration begins March 22 with a tree planting conducted by the Pittsburgh Parks Conservancy.  Who’s going to plant the trees?  Volunteers!

Schenley Park needs you on Sunday March 22, 10:00am to 2:00pm, rain or shine.  Click here or call 412-682-7275 to learn more about signing up.

 

(photos from Bugwood.org by Joseph O’Brien, USDA Forest Service, Bugwood.org and Ronald F. Billings, Texas Forest Service. Screenshot of shared Google map. Click on the map to see details on Google.)

(* Trenching prevents healthy roots from growing into the infected zone.)

UPDATE 2 June 2014: Click here for the most recent update.

Schenley Park Oak Wilt Meeting, Feb 3

Books & Events, Schenley Park, Trees

Back in July I mentioned that there’s oak wilt in Schenley Park.  In the weeks ahead those trees will come down.
Councilman Corey O’Connor is holding an informational meeting about the project on Monday February 3, 6:00pm – 7:30pm at the Jewish Community Center, Levinson Hall B.  (The main entrance is at 5738 Forbes Avenue in Squirrel Hill.)

See Councilman O’Connor’s flyer below for more information.

Schenley Park Oak Wilt meeting, 3 Feb 2014, 6:00pm

The Largest Living Organism

Plants & Fungi, Trees
Armillaria ostoyae (photo from Wikimedia Commons)
Armillaria solidipes mushrooms (photo from Wikimedia Commons)

16 January 2014

On my way to somewhere else I found…

It’s hard to believe these mushrooms represent the largest living organism but they’re the outward and visible sign of a subterranean and under-bark network.

The network can be quite large, as described here on Wikipedia:  “The largest living fungus may be a honey fungus of the species Armillaria ostoyae [now called Armillaria solidipes].  A mushroom of this type in the Malheur National Forest in the Blue Mountains of eastern Oregon was found to be the largest fungal colony in the world, spanning 8.9 km² (2,200 acres) [and] estimated to be 2,400 years old.  … If this colony is considered a single organism, then it is the largest known organism in the world by area.”

And so it was named the “Humongous Fungus.“

There are many species of Armillaria, all with dark shoestring-like rhizomorphs that grow through the soil or under bark and white mycelial fans which spread under bark via root contacts and root grafts.  Here’s what they look like: rhizomorphs on the left, mycelia on the right.  (For a sense of scale, these are tree trunks)

Armillaria rhizomorphs and mycelia (photos from Bugewood.org)
Armillaria rhizomorphs and mycelial fan (photos via Bugwood.org)

Sometimes the mycelia are luminescent and cause foxfire!

Fascinating as their huge size may be, Armillaria spreads widely, infects many trees and can either kill them outright or be a contributing factor to their demise.  This diagram shows how it cycles through the forest.

Armillaria disease cycle (diagram from Wikimedia Commons)

I have seen Armillaria in Schenley Park without realizing what it was: rhizomorphs, mycelia and mushrooms.

Bur oak toppled by armillaria root rot (Joseph O'Brien, USDA Forest Service, Bugwood.org)
Armillaria killed this tree (photo by Joseph O’Brien, USDA Forest Service via Bugwood.org)

So now I understand how a live tree can just fall over when infected by Armillaria root rot.

(photo credits:  mushrooms by Walter J. Pilsak via Wikimedia Commons (click on the image to see the original).  Rhizomorphs and dead tree on grass by Joseph O’Brien, USDA Forest Service via Bugwood.org.  White mycelial fan by Borys M. Tkacz, USDA Forest Service via Bugwood.org)

Two Resins For Tomorrow

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)

Tiny Mistletoe

Plants & Fungi, 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)

Norwegian Gifts

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)

Late November Signs Of Life

Schenley Park, Trees, Winter Weeds & Trees

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)

The Branches Add Up

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

(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.)

Wild Hickory Nuts

Schenley Park, Trees, Winter Weeds & Trees
Shagbark hickory fruits (with husk) and nuts, Oct 2011 (photo by Kate St. John)

27 October 2013

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)