Category Archives: Trees

Hackberries

Hackberries (photo by Kate St. John)
Hackberries (photo by Kate St. John)

Last Sunday in Schenley Park I found these small hard berries littering the trails ... and then one fell on my head.  I looked up to see a flock of robins knocking berries to the ground as they reached to eat them.

It's easy to identify the berries by the bark of their tree.  The common hackberry (Celtis occidentalis) has distinctive layered ridges.

Bark on the common hackberry tree (photo by Kate St.John)
Bark on the common hackberry tree (photo by Kate St.John)

Here's a closeup of one ridge, photographed on a frosty morning.

Hackberry bark in winter (photo by Kate St. John)
Hackberry bark in winter (photo by Kate St. John)

 

Birds eat the berries. Deer eat the twigs.

Deer damage on hackberry twigs, Schenley park, Nov 2017 (photo by Kate St. John)
Deer damage on hackberry twigs, Schenley park, Nov 2017 (photo by Kate St. John)

Hackberry trees provide lots of food for wildlife.

 

(photos by Kate St.John)

Making a Carpet of Yellow Leaves

In autumn ginkgo trees (Ginkgo biloba) turn bright yellow and can lose all their leaves in as little as one day.

Yesterday morning I saw these ginkgos "snowing" so I stopped to film them (11 seconds).  The scene is so bright that it's hard to see individual falling leaves ... but there are many.

I returned six hours later to see if the trees were bare.  Not yet, but close.

Here's the before and after.
Before: 11 November 2017, 10:30am

Ginkgo trees make a bright yellow carpet of leaves, 11 Nov 2017, 10:30am (photo by Kate St. John)
Ginkgo trees make a bright yellow carpet of leaves, 11 Nov 2017, 10:30am (photo by Kate St. John)

After: 11 November 2017, 4:30pm:

Ginkgo trees with considerably fewer leaves, 11 Nov 2017, 4:30pm (photo by Kate St. John)
Ginkgo trees with fewer leaves, 11 Nov 2017, 4:30pm (photo by Kate St. John)

If you want to see ginkgos make a carpet of leaves, I know of two places to go:  Schenley Drive near Phipps Conservatory and Highland Avenue near the entrance to Highland Park.  But watch them soon.  They may be bare by the end of the day.

 

(photos by Kate St. John)

Hope For What We’ve Lost

Fall colors of white ash, 26 Oct 2017 (photo by Kate St.John)
Fall colors of white ash, 26 Oct 2017 (photo by Kate St.John)

Two weeks ago I lamented that fall color is disappointing this year but I should have waited.  The trees in Schenley Park looked better last week with red maples, yellow hickories, and this small tree reminding me of what we've lost.

Those pale green, yellow, orange and violet leaves are on a small ash tree whose trunk diameter is too small to be plagued by emerald ash borer ... and now I've found out why.

Before the emerald ash borer (EAB) invasion, mature ash trees added pastel violet to the splash of color on our hillsides but now only the saplings are left.

Just across the trail from the ash sapling stands a mature ash that's alive, though struggling.  Some upper branches have died back and there are sucker branches below them.  An old emerald ash borer hole shows what the mature tree was dealing with.

White ash tree with emerald ash borer hole in bark (photo by Kate St. John)
White ash tree with emerald ash borer hole in bark (photo by Kate St. John)

The old tree is alive because it received insecticide treatments during the height of the EAB invasion from a program of the Pittsburgh Parks Conservancy and the City of Pittsburgh.   Beginning in 2011, 158 specimen ash trees were treated in the city parks.  This one is #76 according to the metal tag.

White ash tree with tag indicating it is treated for emerald ash borer (photo by Kate St. John)
White ash tree with tag indicating it is treated with insecticide for emerald ash borer (photo by Kate St. John)

Years later it appears that emerald ash borer numbers have dropped and it wasn't because we used insecticides.

Scientists working on EAB biological control in Michigan found that many factors contributed to the emerald ash borer population collapse there.

"Woodpeckers, native and introduced parasitoids, intraspecific competition, disease, innate tree defenses, and reduced ash abundance contributed to the collapse of EAB populations."

Notice that woodpeckers are at the top of the list!

Second on the list are four tiny parasitic insects that kill emerald ash borer larvae.  Two native insects target emerald ash borers through the thin bark of saplings and at Michigan study sites scientists introduced two more parasitic insects from China, the emerald ash borer's homeland, to get through the bark of mature ash trees.

Thanks to the hard work of scientists and arborists we may hope that our ash saplings will grow into mature ash trees.

Read more about ash tree biological controls at this U.S. Forest Service webpage.

 

(photos by Kate St. John)

An Insect Surrounded

Gall on black walnut leaf, 2 Nov 2017 (photo by Kate St.John)
Gall on black walnut leaf, 2 Nov 2017 (photo by Kate St.John)

When an insect laid its egg on this black walnut leaf, the leaf responded by surrounding it to wall it off.

That's exactly what the insect had in mind.  The wall makes it safe.

Now that the leaf has fallen from the tree, I wonder what will happen to the insect.

p.s. I have no idea which gall this is.  Do you know?

 

(photo by Kate St.John)

Disappointing Fall Colors

American beech leaf, 17 October 2017 (photo by Kate St. John)
American beech leaf, 17 October 2017 (photo by Kate St. John)

By now fall colors ought to be at their peak in southwestern Pennsylvania but that isn't the case this year.

Above, an American beech leaf shows hints of green and yellow but is already mostly brown.  The view below at Moraine State Park on Tuesday October 17 shows a landscape that's still green or brown and leafless.  There are no beautiful reds and yellows.

Lake Arthur at Moraine State Park, 17 October 2017 (photo by Kate St. John)
Lake Arthur at Moraine State Park, 17 October 2017 (photo by Kate St. John)

Emerald ash borer killed the trees that used to contribute yellow, orange and violet.  This year September's heat and drought suppressed the maples.

We're still waiting for the oaks to change color but they will turn a muted red.

Maybe next year.

 

(photos by Kate St. John)

Autumn Raptors

Peregrine falcon, Hillary, in autumn in Ohio (photo by Chad+Chris Saladin)
Peregrine falcon, Hillary, in autumn in Ohio, before 2011 (photo by Chad+Chris Saladin)

Today, three scenes of raptors in autumn.

Above, a peregrine falcon flies over the Rocky River.  This photo of Hillary, who nested at the Hilliard Road Bridge in Rocky River, Ohio, was taken by Chad+Chris Saladin prior to 2011.

 

A bald eagle ascends at Glade Dam Lake, Butler County, October 2017.  Photo by Steve Gosser.

Bald eagle at Glade Dam Lake, October 2017 (photo by Steve Gosser)
Bald eagle at Glade Dam Lake, October 2017 (photo by Steve Gosser)

 

A red-tailed hawk migrates south past the Allegheny Front Hawk Watch, October 2012. Photo by Steve Gosser.

Red-tailed hawk flies by the Allegheny FrontHawk Watch, October 2012 (photo by Steve Gosser)
Red-tailed hawk flies by the Allegheny Front Hawk Watch, October 2012 (photo by Steve Gosser)

 

(photos by Chad+Chris Saladin and Steve Gosser)

Wolf Tree

An old dead "Wolf Tree" at Cedar Creek Park (photo by Kate St.John)
A dead "Wolf Tree" at Cedar Creek Park (photo by Kate St.John)

Out in the woods, sometimes dead but often alive, you'll find a large old tree surrounded by a younger forest.  Its branches reach out as if the younger trees weren't there.  It's called a "wolf tree."

Wolf trees are much older than the woods around them.  They were once part of the original forest that was cleared to make a farm.  When the farm was there they stood alone, providing shade for the people and animals.  When the farm was abandoned the forest regrew.

This wolf tree at Cedar Creek Park in Westmoreland County was probably part of the old Greenwood family farm.  The tree died years ago but yet it stands, a gnarled reminder that western Pennsylvania has been through many changes.

See pictures of live wolf trees and read more about them in this article in American Forests magazine:  Wolf Trees: Elders Of The Eastern Forest

 

(photo by Kate St.John)

Webs in the Trees

In the spring we saw tents in the trees.  Now we see webs. Though similar in concept, the structures aren't made by the same species.

The springtime tent, located in the crotch of a tree, is made by eastern tent caterpillars (Malacosoma americanum) who emerge from their tent to eat young leaves as they unfurl.  The webs, located on the branches, are made by fall webworms (Hyphantria cunea) who hide in the web and eat leaves that will fall off in a month or two.

Since late summer female moths have been laying egg masses on deciduous trees.

Fall webworm moth (photo from Wikimedia Commons)
Fall webworm moth (photo from Wikimedia Commons)

After a week the eggs hatch into tiny caterpillars who build a web to completely enclose themselves and their food.  As they eat, they build the web larger to enclose more leaves.

Fall webworms avoid coming out of the web until they're ready to pupate. Then they hide their cocoons under flaps of bark to overwinter and emerge next year.

Though the webs look ugly they don't harm the trees because the leaves will drop soon anyway.

See webworms in action in the video above from The Capitol Naturalist in D.C.  Read more in this vintage article from 2011:  Coming Soon To A Tree Near You

 

(photo of fall webworm moth from Wikimedia Commons; click on the image to see the original)

Woodpeckers Are Doing Really Well

Pileated woodpecker, April 2012 (photo by Chuck Tague)
Pileated woodpecker (photo by Chuck Tague)

Last week Pittsburgh Today published a brief article about ecosystem health in the Pittsburgh region.  One of their points caught my eye: Pileated woodpeckers (Dryocopus pileatus) have made a big comeback in our area.

I've noticed this too.  During Pittsburgh's 2016 Christmas Bird Count last December, many of us found pileated woodpeckers -- so much so that Audubon's summary of the count included this remark: "Pileated Woodpecker was reported at a higher than expected number.  48 individuals represents a new high count for Pittsburgh. "

On the same day as Pittsburgh Today's article, I also received an email from Tree Pittsburgh with news about a project this fall to replace ash trees lost to emerald ash borer (read more here.)

Without intending it, the topics are related.  My hunch is that we have more pileated woodpeckers in Pittsburgh because we have more under-the-bark insects and more dead and dying ash trees, suitable for nesting, since the emerald ash borer came to town 10 years ago.

Pileated woodpecker hole in dead white ash tree, Pennsylvania (photo by Kate St. John)
Pileated woodpecker hole in dead white ash tree, western Pennsylvania (photo by Kate St. John)

 

Woodpeckers are doing really well.  It's the only bright spot in the emerald ash borer plague.

 

(photo credits: Pileated woodpecker by Chuck Tague.   Dead ash tree with pileated woodpecker hole by Kate St. John)