Category Archives: Winter Weeds & Trees

Winter Trees: Hophornbeam or Ironwood

No matter how you look at it, this tree has confusing names.  My Winter Tree Finder calls it ironwood (it doesn't even list the hophornbeam name!), but as I learned last weekend ironwood is an alternate name for at least two other trees.

Ironwood's official name is eastern hophornbeam (Ostrya virginiana).  It's a common tree in the birch family, most easily recognized by its bark which has long, square-edged strips that peel upward.

Hophornbeam wood is very heavy, hard and strong, so durable that when metal was scarce this wood was used to make wheel rims and sleigh runners.  "Horn beam" means hard wood.  "Hop" refers to the tree's fruit which resembles hops (think beer).  Here's what the fruit looks like:


A closely related tree, the blue beech (Carpinus caroliniana), also carries the hornbeam and ironwood names.  Blue beech's official name is American hornbeam without the "hop."  Its bark looks very different:  smooth, blue-gray and muscular.  This earned it the nickname "musclewood."   Click here to see blue beech bark.

Since hophornbeam is in the birch family, its twigs look very "birch-y" and often carry catkins.  From experience with the Winter Tree Finder, I can tell you it takes a long time to key out this twig.  I recommend identifying the tree by its bark.


Ironwood and ironwood, hophornbeam and hornbeam.  I'll keep them straight by calling this one hophornbeam (or ironwood) and the other one "blue beech" instead of its confusingly similar hornbeam name.

(Bark and twig photos by Kate St. John.  Hop-like fruit photo from Wikimedia Commons.  Click on the hops photo to see its original.)

Winter Tree Walk: Let’s Look at Bark

Sixteen of us gathered at Schenley Park yesterday for a walk among the trees.

As we left the Visitors Center we were treated to far away(!) views of Pitt's peregrines, Dorothy and E2, sunning on the south face of the Cathedral of Learning. The weather cooperated and the sun came out.

Here we are in the woods just before we began the mind-numbing task of keying out twigs using the Winter Tree Finder.  By the third twig we had had it!  We gave up on twigs and switched to bark.  Thanks to Debbie Bryant for bringing the Bark book.

Right off the bat I learned something new.  When I identified a tree as "ironwood" George Bercik said ironwood was a different tree.  We consulted our field guides and discovered that "ironwood" is the common name for two trees.  I call the eastern hophornbeam "ironwood."  George calls the American hornbeam "ironwood" (which I learned as "blue beech").   Both names are correct but confusing.  That's the problem with common names...

On our route we found black cherry's "burnt potato chip" bark, dark red oaks, pale beech trees, and hackberry's "pie crust" bark.  Birds were few but we saw an adult red-tailed hawk hunting in the woods and some gulls flying overhead.

Around 2:30pm the wind picked up so we returned to the Schenley Park Visitor Center for hot chocolate.   What a cozy end to our bark walk.  Thanks to everyone for coming.

p.s. Spring must be coming soon.  The daffodils are up at the Visitors Center.

(photos by Kate St. John)

Confirming: Winter Tree Walk Tomorrow

The Winter Tree Walk is "on" as planned, 1:00pm to 3:00pm tomorrow, February 18.  Click here for directions and details.

Expect overcast skies and temperatures 43-45 degrees with some wind and a slight chance of rain.  It will feel like 38-40 degrees.

Dress warmly.  Wear boots.  Most of our route is sidewalk or crushed gravel but be prepared for one 60-foot muddy stretch.  (Route is shown above in red.  See map key below.)  Feel free to bring a hiking stick.  I'm bringing mine for walking and for pointing out trees.

Bring quarters for parking!  Parking rates are $0.25 for 7.5 minutes = $2.00/hour.  For 2 hours you'll need at least 16 quarters.  More is better.  Note: The white laminated "No Parking" signs attached to the meters ask you not to park from 5:00am - 9:00am because of CMU buggy practice.  Our outing is 4 hours after the "no parking" time, so don't worry.

Post a comment if you have a question (comments send me email) or call me at 412-622-6558.  I'll be checking for comments & messages until 1:00pm on Saturday.

See you tomorrow.

(screenshot of Schenley Park from Gmap Pedometer.  Pink circle is Schenley Park Cafe & Visitor Center.  Red is our route.  Green line is location of free parking with dots indicating walking route to the Visitor Center.)

Winter Trees: Sycamore

From a distance this massive white tree looks like a ghost in the valley.

It's an American sycamore (Platanus occidentalis), also called buttonwood or American planetree.  In Pittsburgh we call it a sycamore but in other countries this name can be confusing because it refers to other trees.  In Europe the "sycamore" is a maple.

American sycamores are native to eastern North America from Maine to Texas, from Ontario to Florida.  You'll find them along creeks and rivers, in bottom land but not in swamps.  They like to be near water, but not in it, because they'll die if their roots are submerged continuously during the growing season.

Sycamores are easily identified by their bark which flakes off in big chunks to reveal the pale new bark beneath.  They do this because their bark cannot expand as the tree grows.  Look up the tree trunk and you'll see the characteristic ghostly white color.


In rural settings you can safely identify the flaky bark as a sycamore but in town we've planted London planetrees, a hybrid of the American sycamore and Oriental plane tree.  The new bark on London planetrees is greenish-beige where the sycamore is white.

The seed balls of both species stay on the tree through the winter, breaking up in early spring. Each seed has a bit of fluff attached to help it disperse by wind or water.

One way to tell the difference between American sycamores and London planetrees is to look at the seed ball stems.  On sycamores there is generally one seed ball per stem.  On London planetrees two or three hang from the same stem.


Sycamore twigs zigzag from bud to bud. The buds form underneath the petioles (leaf stems) during the growing season and don't appear until the leaves fall off.  Each bud is encased in a single scale and surrounded by the leaf scar.


Sycamores (and London planetrees) are both noted for their very large trunks which often become hollow with age.  Champion trees have been measured at 167 feet tall with trunks 13 feet in diameter.  The oldest trees are the largest.  They can live for several hundred years.

(photos by Kate St. John)

Reminder: Meet me at Schenley Park Cafe &Visitors' Center at 1:00pm this Saturday for a Winter Tree Walk to practice your winter tree identification skills.  So far the weather looks good (above freezing with no precipitation!).  Click here for more information.

Winter Trees: Black Cherry

Today's tree is easy to identify all year simply by looking at its bark.

Black cherry (Prunus serotina) is a medium to large tree, 50 to 100 feet tall.  Mature trees have dark colored bark that looks like burnt potato chips.  The shadowy photo above accentuates the chips.

In bright light the trunk looks paler but the chips are still there, as you can see by this photo taken in full sun.


Young trees have smooth shiny bark with pale horizontal lines or lenticels.  Even the twigs have lenticels that appear as spots in the picture below.  The buds are alternate, small and scaled.  This twig looks like it wants to open its buds, proof that it's been a weird warm winter.


Black cherries are a favorite of birds in late summer because the trees produce an abundance of small red to purple cherries, 1/3" in diameter.  Foresters like the tree for it's cherry-colored wood which fetches a good price.

Keep your eyes open for black cherry trees and you'll be surprised how many you find.

(photos by Kate St. John)

Winter Trees: Black Locust

A friend of mine from Maryland once remarked that Pittsburgh has ugly trees.  "The gnarled ones look like devil trees," she said.

Though she didn't know their name I think she was referring to black locusts whose winter profile can look spooky.

Black locusts (Robinia pseudoacacia) grow in twisted shapes if they've been broken, badly trimmed, or invaded by the locust borer that weakens and deforms the tree.  The tree pictured above has been through at least two of these assaults.

The bark on mature black locusts is gray-brown and so deeply furrowed it looks distressed. Though a bit spooky it's a good field mark for identifying the tree.


Up close you can see that each bud is surrounded by paired thorns, like devil's horns.


The thorns also grow on the trunks of young trees.


Black locust flowers are such good honey-sources that they've been planted for this purpose in Europe, Asia and southern Africa.  If you don't live in the black locusts' native range -- the southern Appalachians from Pennsylvania to Georgia, and the Ozarks -- you might think of them as devil trees where they've become invasive.

Black locusts thrive in old fields, disturbed woodlots and along roadsides because they tolerate pollution and poor soil.  They make their own fertilizer through a process called nitrogen fixation.  As members of the legume family, their roots have a symbiotic relationship with Rhizobium bacteria.  The bacteria enters the root hairs and the plant makes tumor-like growths to surround it.  This protects the bacteria which in turn takes in nitrogen and converts it to a form that fertilizes the plant.

With beautiful flowers and an ability to make fertilizer, they don't deserve to be called devil trees.

(photos by Kate St. John)

Winter Trees: White Oak

Continuing the oak theme, today's tree is the Eastern White Oak (Quercus alba).

As I said last week, Pittsburgh's natural habitat is the oak-hickory forest.  In this part of North America oak species fall into two groups: reds and whites.  Red oaks are typically found in oak-dominated forests.  White oaks are so versatile they can grow in many habitats and have one of the widest ranges of any tree on the continent.

White oaks are majestic trees -- as much as 150 feet tall, four feet in diameter, and 600 years old.  Like all oaks they produce acorns and have clusters of buds at their twig tips.  You can distinguish them from red oaks because their leaves have rounded lobes, their buds are smaller and blunter, their acorn cup scales are paler, knobby and the cup is not hairy inside, and their bark is paler, scaly and sometimes peeling.

The blunt buds, clustered at the twig tip, are pictured above.  As you can see, a few dried leaves remain on the tree in the winter.

The bark at the base of the tree is a good hint to this tree's identity because it looks as if part of it was rubbed off.  Here are two examples.  (It's easier to see the "rubbed off" appearance in real life than in photos.)

Look up the tree trunk and you'll see paler, slightly peeling bark and a few dried leaves.

White oaks are famous for producing bumper crops of acorns every 4-10 years.  A single tree can produce 2,000 to 7,000 acorns so you can imagine the effect in an area with a lot of white oaks.  One fall in the Laurel Highlands there were so many acorns that I found it hard to hike without slipping on them!

Squirrels eat acorns from both red and white oaks but they treat them differently.  They bury red oak acorns and eat the white oaks' right away.  Red oak acorns are full of tannin (less palatable) and don't sprout until their second spring.  White oaks have less tannin and sprout in their first spring.  Burying reds and eating whites makes sense.  Red oak acorns can be placed in underground storage.  White oaks would sprout before the squirrel could get back to them.  Smart squirrels, eh?

(photos by Kate St. John)

Winter Tree Walk at Schenley Park, Feb 18, 1:00pm


Here's a chance to practice the winter tree identification skills I've been blogging about on Wednesdays.

On Saturday, February 18, 1:00pm - 3:00pm, I'll lead a Winter Tree Walk in Schenley Park.

Meet me at the Schenley Park Cafe and Visitor Center at 1:00pm and we'll walk the trails to see some of the trees I've highlighted.

Bring a field guide or the Winter Tree Finder, binoculars or a hand lens so you can see the details, and quarters for the parking meter (unmetered parking is a bit of a walk).  Prepare for cold weather and dress warmly.  We'll be moving at the speed of botany (slowly!) so expect to be standing out in the cold.

For directions to the Visitor Center, click here and scroll down to the heading: "Directions to Schenley Park Cafe and Visitor Center, 101 Panther Hollow Road."  The Visitor Center is open from 10am to 4pm with food and hot chocolate.  Come early and eat lunch.  Here's the menu.

I hope February 18 will be as nice as the day in December when I took this photo.  Watch my blog on the morning of February 18 for final details.

Hope to see you then.

(photo by Kate St. John)

p.s. If you have questions, leave a comment.  I moderate the comments so I'll be able to read and respond privately.

Winter Trees: Red Oak

If you've traveled around the country you may have noticed there's a different mix of trees outside of Pittsburgh.  Compared to other parts of North America, southwestern Pennsylvania has few pines and spruces, no white birches (unless planted) and no mangroves.  But we do have a lot of oaks and hickories.

Pittsburgh's habitat type is the oak-hickory forest, the widest ranging deciduous forest type in eastern North America.  Oak-hickory forests are dominated by oaks and hickories (of course) and are home to birds and animals who eat the acorns and nuts: blue jays, wild turkeys, gray squirrels,  fox squirrels and eastern chipmunks.

The northern red oak (Quercus rubra) and eastern black oak (Quercus velutina) are indicator species for the oak-hickory forest.  Both are in the red oak group, are very similar and even hybridize. For purposes of this simple tree guide I'll help you recognize "red oaks."

All oaks produce acorns and have a cluster of buds at the tip of the twig. In eastern North America oaks fall into one of two groups: reds and whites. Here are the differences between them:

  • Red oak group:
    • Leaves have pointed or bristly tips on each lobe
    • Buds have pointed tips and are larger than white oaks' buds
    • Acorn cup scales are brownish and flat; the cup is hairy inside
    • Bark is generally dark, smooth or ridged but not peeling
  • White oak group:
    • Leaves have rounded lobes
    • Buds are blunted, rounded and generally smaller
    • Acorn cup scales are knobby and paler; cup is not hairy inside.
    • Bark is paler, peeling from higher trunk and branches, looks as if it was rubbed off at the base of the tree.

Notice in the photo above how the buds are clustered at the tip and are pointed.

Red oak bark is dark and doesn't peel.  Even though it has ridges, the ridge tops still have a smooth appearance.


Oaks have bumper crops of acorns every few years on a cycle that's determined by species.  Red oaks cycle every 3-4 years; white oaks every 4-10 years.  This abundance and scarcity causes a fluctuation in those who eat the acorns, too.

Sometimes you can recognize oaks from afar because their crowns are massive, wide and spreading.  Here's a red oak seen from a distance in Schenley Park.


Interestingly, the red oak is the dominant oak in Schenley Park and often has a reddish tinge in the bark's furrows or on the surface.  I'm not sure why or even if this tinge is diagnostic.  (See the slight reddish tinge in the bark furrows above.)

(photos by Kate St. John)

Winter Trees: Norway Maple

No discussion of western Pennsylvania's trees would be complete without including the Norway maple (Acer platanoides).

As its name suggests this tree is native to Europe, growing as far north as Norway, south into Greece and Iran, east into Russia.  It was brought to North America as an urban shade tree because it survives well in compacted soil and air pollution.

Unfortunately it survives too well.  The Norway maple naturalized on this continent and easily became invasive because it releases chemicals in the soil that inhibit the growth of underbrush and native saplings.  In addition, native animals and insects prefer to eat North American maples more than this import. With these competitive advantages it's no wonder you can find pure stands of Norway maples with bare ground beneath them.

Normally I recognize Norway maples by their twigs and buds.  The buds are opposite on the stem, reddish and turban-shaped with a slightly larger end bud.  In the photo above, taken in Schenley Park in November, the twig is green with reddish turban-shaped side buds and an end bud that looks like it's opening.  The twig below conforms more closely to the typical description of Norway maple buds.  There are many cultivars in Schenley Park including a variety with purple leaves so my photo may differ for that reason.


Norway maple seeds are easy to recognize because the samaras are nearly 180 degrees apart.  Other maples have "wings" that droop.  You'll see some of these seeds and their stalks on the trees in the winter.


The bark on young Norway maples looks almost smooth, just faintly striped.


On older trees it has narrow stripes and shallow furrows.

Norway maples are easiest to recognize in late fall because they're out of synch with our seasons.  They retain their yellow leaves into mid or late November and lose them only after our native maples are bare.

(photos by Kate St. John except UGA0008518 by Paul Wray, Iowa State Univ and UGA5306048 by Steve Hurst, USDA, both from