Category Archives: Trees

Tiny Opals

Hackberry fruits (photo by Paul Wray, Iowa State University, bugwood.org)

This month I read Lab Girl by Hope Jahren and learned that she made an amazing discovery in 1998 during research for her doctoral dissertation:  Inside common hackberry fruit is a small hard pit with a lattice made of opal.

Hackberry fruits, pictured at top, are drupes similar to cherries and peaches with fleshy fruit surrounding a central pit.  The fruit is thin and the pits are large so we rarely eat hackberries but birds love them.

The pits in cherries and peaches are made of wood (or something like it) but hackberry pits are made of stone: calcium carbonate inside a lattice framework. When Hope Jahren used Xray diffraction on the crushed lattice material its composition came up “opal.” 

When I found this out I searched for the pits under hackberry trees in Schenley Park. At this time of year the fleshy purple fruit is gone, only the white pits remain.  Here’s what I found, one whole, one opened. The exterior is a network of tiny raised lines. 

Opal is in these hackberry pits (photo by Kate St. John)

The pits don’t look like opal and probably never will.  You’d have to use acid to remove the calcium carbonate (the white stuff of seashells) and then examine the remaining latticework under a microscope.  There’s a tiny bit of opal in there.

And so I wonder: How does a tree put opal in its drupes?  I don’t know, but here are the raw materials:

[The rock] Opal is formed from a solution of silicon dioxide and water. As water runs down through the earth, it picks up silica from sandstone, and carries this silica-rich solution into cracks and voids, caused by natural faults or decomposing fossils. As the water evaporates, it leaves behind a silica deposit. This cycle repeats over very long periods of time, and eventually opal is formed. 

From Opals Down Under

Trees take up water that contains dissolved minerals including the building blocks of opal.

Miraculously, the hackberry tree pulls out what it needs and makes an opal latticework inside its drupes.

Learn how to identify hackberry trees in winter at Winter Trees; Hackberry.  Then search the leaf litter for tiny opals.

For further reading see : Hackberry: A Gem of a Weed

(photo credits: hackberry fruits by Paul Wray, Iowa State University, bugwood.org, hackberry pits by Kate St. John)

The Trees Are Still Standing

Camp Fire damage in a Paradise, California, neighborhood, Nov. 17, 2018 (photo by Senior Airman Crystal Housman, California Army National Guard)

In all the smoke-filled photos of the Camp Fire devastation in Paradise, California one thing stands out to me:  The buildings are gone but the trees are still standing.

The town of Paradise, California (population 26,000) was destroyed on 8 November 2018 by the Camp Fire, the deadliest and most destructive fire in California history.  As soon as it ignited at 6:30am, the fire raced westward on 50-70 mph winds. By 8am it reached the Paradise Town Limit six miles away. Seven towns were forced to evacuate but not everyone made it out. As of 26 November, 88 are confirmed dead, 203 are still missing and tens of thousands are left homeless.

But the trees survived.  You can see them in all the photos and videos including these taken on 17 Nov by the California National Guard as they searched the rubble and marked the damage. 

Soldiers from the California Army National Guard’s 649th Engineer Company, Chico, conduct search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

Because the trees are still standing, the damage assessment has to be done by hand. This Washington Post article shows how the satellites can’t see through standing trees. 

So why are the trees OK in this incinerated landscape? I’m sure it has to do with moisture.

U.S. Army Sgt. Rodrigo Estrada of the California Army National Guard’s 649th Engineer Company, Chico, leads a team conducting search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

Living trees contain more moisture than the dry wood in buildings. When blowing embers hit houses, they catch fire immediately. The trees’ moisture resisted. The fire moved on.

This video by Mike West shows how quickly fire consumes dry wood compared to living trees.

The scene is spooky now. Nearly everything is gone but the trees are still standing.


Soldiers from the California Army National Guard’s 649th Engineer Company, Chico, conduct search and debris clearing operations, Nov. 17, 2018, in Paradise, CA (photo by Senior Airman Crystal Housman)

p.s.  Some trees are damaged and will fall sooner or later.  Here’s an NPR story about trees in the fire zone.

p.p.s. See the damage extent on Cal-Fire’s Camp Fire Structure Status map.  See satellite images here in the Washington Post

(photos by Chico California National Guard, YouTube video by Mike West)

Snow On Leaves

Snow on leaves, Schenley Park, 16 Nov 2018 (photo by Kate St. John)

On Thursday it rained. Then it sleeted. Then it snowed in the wee hours of Friday morning, especially north of Pittsburgh.

In the old days most of the trees would be bare by now, but this year many still have leaves.

Ice and snow made the leaves heavy and some of the trees came down, hitting power lines as they fell.  By Friday morning KDKA reported that 65,000 households north and east of the city were without electricity.  No power, no heat, and for those with well water, no water.  It may take until Sunday evening to get all of the power restored..

The City is warmer than surrounding counties so Schenley Park had snow on the leaves, but no ice.

Snow on leaves, Schenley Park, 16 Nov 2018 (photo by Kate St. John)

Here’s what my favorite hillside looked like yesterday. 50% of the trees still have leaves.

Only half of the trees are bare, Schenley Park, 16 Nov 2018 (photo by Kate St. John)

The power failures wouldn’t have been so bad if most of the trees had been bare. 

(photos by Kate St. John)

Watch for Witch Hazel

Witch hazel flowers catch the light after the leaves are gone, November (photo by Kate St. John)

When the leaves are gone these lacy flowers stand out in the forest.

American witch hazel (Hamamelis virginiana) blooms from late October into December in eastern North America.  Its delicate yellow flowers smell like lemon.

Witch hazel flower, October in Schenley Park (photo by Kate St. John)

Since witch hazel blooms when few insects are out how are the flowers pollinated?

In 1987 Bernd Heinrich found that owlet moths come out at night to sip the flowers and thereby pollinate them.

The moths survive cold weather by hiding under leaf litter during the day, then shivering to warm up and fly at night. Click here to learn more.

(photos by Kate St. John)

When Will Most Of The Trees Be Bare?

Leafless bur oak, Schenley Park, 4 Nov 2011 (photo by Kate St. John)

Every year I record the date when most of the trees are bare on my favorite hillside in Schenley Park — the hill at the end of the Greenfield Bridge.

In 2008 the leaves were gone by 2 November.  In 2012 Hurricane Sandy stripped them from the trees by 4 November.

Last year the changes happened much later. In 2017, the leaves were still green in late October and more than half were still on the trees on 27 November.  Here’s a 2017 slideshow of autumn trees on that hillside.

  • 26 October 2017: Lots of green at the end of October 2017.

This year is similar to last so I wonder … When will most of the trees be bare?  November 15?  20?  30? Later?

Let me know how the trees look where you live and vote for the date “When Most of the Trees Will Be Bare” by leaving a comment below.

HINT!  Two factors that affect leaf loss on this hillside:  (1) More than half of the trees are oaks; oaks drop their leaves later than maples.  (2) This city location is warmer than surrounding counties.

(photo by Kate St. John)

Stinky Fruit

Ginkgo tree with fruit, October in Schenley Park (photo by Kate St. John)

It’s time to tiptoe on the sidewalk at Flagstaff Hill.  The female ginkgo trees are dropping their smelly fruit on Schenley Drive. 

Ginkgo fruit on the sidewalk at Schenley Park (photo by Kate St. John)

Ginkgo fruit smells like stinky feet or vomit but the nuts inside are edible.

On Throw Back Thursday, learn about ginkgos in this 2011 article: Stinkbomb Tree.

(photos by Kate St. John)

Fall Foliage: When?

Moraine State Park, 15 Oct 2017 (photo by Kate St. John)

Summer ended on Friday morning. Brrrr! Now that it’s cold, it’s time for colorful fall foliage, right?

Some reports say western Pennsylvania won’t have pretty leaves this fall, others say we will.  One thing is certain, though. The leaves stayed green longer than usual.

Twenty years ago our fall foliage reached its peak around October 15 but today — only one day before the 15th — the leaves have just begun to change.  We had the same situation last year as shown in my photo taken at Moraine State Park on 15 October 2017.

Delayed timing makes it hard to know when fall color will reach its peak but the Pennsylvania Bureau of Forestry (DCNR) is here to help.  Check out their Fall Foliage Guide complete with an interactive map and weekly reports.  The October 11-17, 2018 forecast map is shown below (yellow means “approaching best color”). Click here or on the caption to see the full report.

screenshot of Pennsylvania Fall Foliage Report, Oct 11-17 2018, by PA DCNR

Don’t worry if you haven’t gone “leaf peeping” yet in western Pennsylvania.  You still have time to see fall colors this month.

(photo by Kate St. John, Screenshot from the Pennsylvania Fall Foliage Report, October 11-18, 2018, PA DCNR; click on the caption to see the original)

Un-Confusing Conifers

Eastern hemlock cones and foliage in Kentucky (photo from Wikimedia Commons)

I’m pretty good at identifying western Pennsylvania’s deciduous trees because I live with them, but evergreens aren’t common here and they confuse me.

After I flunked the spruce-fir-hemlock test in Newfoundland in July I vowed to learn from that experience and do better last month in Maine.  I updated my conifer “cheat sheet” and memorized the difference between balsam firs and hemlocks.

Conifers are still confusing but I’m doing better.  I got a B- in Maine.

How do you tell the difference between pines, spruces, firs and hemlocks?
Learn from my conifer cheat sheet: In A Coniferous State.

 (photo from Wikimedia Commons; click on the caption to see the original)

What Made This Tree Fall?

Three Duquesne Light trucks at fallen oak on Bartlett Street, Schenley Park, 30 Sept 2018, 6:40pm (photo by Kate St. John)

Yesterday morning this oak was intact as we searched it for warblers in Schenley Park.  Last evening three Duquesne Light trucks were parked below it, fixing the wires it hit when a big chunk fell on Bartlett Street.

Here’s what broke (photo below). Most of the tree still stands but I wouldn’t be surprised if DPW chops it down now that it “misbehaved.”

Oak branch broke and fell on Bartlett Street, Schenley Park, 30 Sept 2018 (photo by Kate St. John)

This is not the only 100-year-old oak that’s fallen in the park in recent weeks.  This oak fell across the Falloon Trail in July …

Oak tree fallen across the Falloon Trail, 18 July 2018 (photo by Kate St. John)

… and this one fell last week at the edge of Overlook Drive.

Oak down on Overlook Drive, Schenley Park, 30 Sept 2018 (photo by Kate St. John)

None of the crashes were caused by strong wind. The trees just broke and fell.  The Fallon and Overlook trees had root rot, caused by Armillaria fungus. (See below for more on the Bartlett tree.)

You can see it inside this fallen trunk: black sheets of old Armillaria and white sheets of mycelium, the new growth, in the center.

Root rot inside fallen oak, black Armillaria rot and white mycelium (photo by Kate St. John)

If this stump was damp on a warm, very dark night (impossible in Schenley Park) the fungus would glow in the dark — a phenomenon called foxfire.

We usually don’t know that a tree is infected but the fungus will give us a hint this month.  Armillaria produces fruit in autumn that we call honey mushrooms.  (Here’s a USDA photo of one species, Armillaria tabescens.)

Armillaria tabescens at the base of a young oak (Theodor D. Leininger, USDA Forest Service, Bugwood.org)

If you find honey mushrooms at the base of a tree, that tree is infected.

Unfortunately there’s a lot of Armillaria in Schenley Park.  I’ll look for mushrooms this month to find out who’s in trouble.

NEWS about the Bartlett tree: The branch that fell on Bartlett Street was hollow — probably not Armillaria but it was bad nonetheless.  Here’s a photo of the thickest part of the branch after it was chopped up.

Inside of hollow branch that fell on Bartlett Street, 30 Sept 2018 (photo by Kate St. John)

p.s.  Yes there are mushrooms in the city parks but it’s illegal to harvest them, even for personal use.

(Schenley Park tree photos by Kate St. John. mushroom photo by Theodor D. Leininger, USDA Forest Service, Bugwood.org)