Category Archives: Trees

Catkins And Tiny Flowers

Phenology, Trees
American hazelnut with catkins (photo by Kate St.John)
American hazelnut with catkins (photo by Kate St.John)

Every year I see these yellow catkins in March and every year I forget their name.  But this year will be different.  I’m identifying them ahead of time as American hazelnuts (Corylus americana).

The catkins are the male flowers, so full of pollen that your fingers become dusty yellow if you touch them.  They swing and flutter in the breeze to disperse their pollen to …

American hazelnut catkins, early March 2012 (photo by Marcy Cunkelman)
American hazelnut catkins, early March 2012 (photo by Marcy Cunkelman)

… to fertilize this tiny flower.  The red female flowers, located on the branches, are easy to overlook because they’re so small.  They don’t stand out because they don’t need to attract insects for pollination.

Female flower of the American hazelnut (photo by Marcy Cunkelman)
Female flower of the American hazelnut (photo by Marcy Cunkelman)

Here are some additional tips on identifying American hazelnut:

  • This nut-bearing plant is often cultivated. It produces more nuts in full sun but it grows in the shade as well.
  • American hazelnut trunks grow in clumps like a shrub.
  • The clumps are on average about 10 feet tall.
  • Its long yellow catkins indicate it’s in the birch family.
  • The bark is smooth and speckled.
  • Many of the catkins sprout alone instead of in bunches.
  • The catkins are as long — or longer — than my fingers.
  • The leaf buds are alternate on the branches.
  • The female flowers bloom from the leaf buds before the leaves appear.

Because it’s often cultivated, you’ll find American hazelnut along trails and in easy to reach places. Its nuts provide food for wildlife.

 

(photos credits: top photo by Kate St. John, closeups by Marcy Cunkelman)

The Trees Get An Early Start

Trees
American elm flowers about to open, 3 March 2018 (photo by Kate St. John)
American elm flowers about to open, 3 March 2018 (photo by Kate St. John)

Even though March came in like a lion, the trees remember that it felt like summer last month so they’re waking up for spring.

American elms (Ulmus americana) are one of the first trees to bloom and have already begun in my city neighborhood.  Right now it’s easy to recognize young elms from afar because their twig arrangement resembles a fish skeleton dotted with reddish flower buds.  The skeleton isn’t perfect though. The “ribs” (twigs) alternate up the branch.

American elm branches with buds opening, 3 March 2018 (photo by Kate St. John)
American elm branches with buds opening, 3 March 2018 (photo by Kate St. John)

The trees with opposite twigs and fat red buds are red maples.  They’re blooming, too.

On the last day of February at Raccoon Creek Wildflower Reserve, the top bud on this pignut hickory was pushing out tiny leaves.  This is so premature that it reminds me of the early leaf out we had in March 2012.

Pignut hickory twig, Raccoon Creek Wildflower Reserve, 28 Feb 2018 (photo by Kate St. John)
Pignut hickory twig, Raccoon Creek Wildflower Reserve, 28 Feb 2018 (photo by Kate St. John)

And though the sycamores looked dormant next to Raccoon Creek …

Sycamores on the banks for Raccoon Creek, Beaver County, PA, 28 Feb 2018 (photo by Kate St.John)
Sycamores on the banks for Raccoon Creek, Beaver County, PA, 28 Feb 2018 (photo by Kate St.John)

… their seed balls are ready to disintegrate in the wind.

Sycamore seed balls hanging like ornaments, 3 March 2018 (photo by Kate St.John)
Sycamore seed balls hanging like ornaments, 3 March 2018 (photo by Kate St.John)

 

Will this weekend’s cold weather delay the trees?  I hope so!

 

(photos by Kate St. John)

It Just Fell Over

Schenley Park, Trees
Red oak fell over in Schenley Park as seen on 17 January 2018 (photo by Kate St. John)
Red oak fell over in Schenley Park, as seen on 17 January 2018 (photo by Kate St. John)

Sometimes soggy ground is too weak to hold a mature tree.

On Friday January 12 it rained 2 inches in 24 hours in Pittsburgh.  Then it got very cold.

This red oak was rooted in a hillside in Panther Hollow but it began to lean after so much rain.  By January 16 it blocked the Upper Trail in Schenley Park.  The Park Ranger vehicle can’t come through.

Alas, it just fell over.

 

(photo by Kate St. John)

 

Hackberries

Deer, Schenley Park, Trees
Hackberries (photo by Kate St. John)
Hackberries (photo by Kate St. John)

18 November 2017

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

Trees
Ginkgo leaves falling (video by Kate St. John)

12 November 2017

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

Insects, Trees

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)

(*) Emerald ash borer was first discovered in Michigan and Ontario in the summer of 2002.  It was confirmed in western Pennsylvania in June 2007.

An Insect Surrounded

Insects, Trees

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

Trees, Weather & Sky

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)