It’s winter. Mostly. The plants are dormant but there’s no snow to brighten the ground. With temperatures in the 40’s and overcast skies the landscape is brown in Pittsburgh.
But what is this? A spot of green on this last day of 2011. What plants are braving the cold in Schenley Park?
Two alien invasives:
Goutweed …
… and Garlic mustard.
Perhaps it’s not wintry enough for them.
(photos by Kate St. John)
The tuliptree (Liriodendron tulipifera) is easy to identify by its leaves, flowers, fruits and seeds but more of challenge when you’re limited to twigs and bark.
In early winter, look up and you’ll find the tree dotted with upright, drying fruits shaped like flowers. Each one is a seed cluster of samaras attached at the base of the “flower.”
As time passes, the fruits dry and the samaras blow away from the tree or fall to the ground below. They look like rounded skis with a lump at the toe.
In the absence of these clues examine the twigs, trunk and bark.
The reddish-brown twigs are less than 1/2 inch thick and have alternate leaf buds with a single large end bud shaped like a duck’s bill. This shape is your big clue that it’s a tuliptree. I’ve read that this bud encloses the nascent leaves until the frosts are past, then the leaves unfurl like wings. Also notice the stipule scar that surrounds the twig where the leaf used to be.
I’ve seen both reddish-dark-gray and deep-red end buds in Schenley Park. Dark gray is shown in the first photo, deep red below:
Identifying the tree by its bark is another story. The best clue is the shape of the trunk. It’s very straight and tall with no lower branches because these trees grow so fast. Tuliptrees are shade intolerant and put all their energy into the trunk during their surge to the sun. Along the way they drop their lower branches and leave a big upside down smile on the bark where the branch used to be. This is noticeable on younger trees whose bark has flat-topped ridges with lighter furrows, shown here:
On older trees the ridges look less flat-topped, the furrows aren’t as light and the smiles are hard to find, though you will see horizontal line breaks in the bark:
When young tuliptrees reach the top of the canopy, their crowns are shaped like candle flames which they resemble when their leaves turn yellow in autumn. They drop their leaves from the bottom first leaving a few fluttering leaves at the top in late November as the “candles” are going out.
Perhaps the fluttering yellow leaves gave them the alternate name of yellow-poplar. The tuliptree is not a poplar, though. It’s in the magnolia family and will have beautiful flowers in the spring.
(Buds and bark photos by Kate St. John. Samara and young bark photos from Wikimedia Commons. Autumn tuliptree by John Ruter, Univ of Georgia at Bugwood.org. Click on the captions to see the originals.)
Many of you already know the American beech tree (Fagus grandifolia) by its smooth, pale gray bark. The bark is so pale that it stands out in the forest and so smooth that people sometimes carve their initials in it. When you see a pale, gray, smooth trunk whose bark has carvings you know you’ve found a beech.
Mature beech trees are large, often 50-70 feet tall. Their main trunk is relatively short then the tree spreads out in slender branches. They often grow in pure stands in the forest but this can be their undoing. When one gets beech bark disease it spreads to the entire stand. I’ve seen this sad outcome in the Gallitzin State Forest near the John P. Saylor Trail. Like many tree diseases, this one is caused by an imported pest.
Small beeches are eye-catching in winter because they retain their leaves. The pale, paper thin leaves become paler as winter progresses and they rattle and dance in the wind, drawing attention to their understory host. Here’s a twig showing the leaves still attached in early winter:
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Step closer and you’ll see that the twig is slender with alternate buds. Each one is nearly an inch long and angled away from the twig. In this closeup you can see the bud has many scales. Eight or more is diagnostic according to the Winter Tree Finder.
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If you’re lucky you’ll find beech nuts under the tree. The husks are 4-sided, spiny and burst open to reveal one to three seeds inside. These husks had two nuts each.
Beech nuts are good food for wildlife so you’re unlikely to find them in late winter… But now you can easily find a beech.
(photos by Kate St. John)
Early this month our sunny, dry weather allowed these milkweed pods to slowly release their seeds in Schenley Park.
Each brown seed emerged with a fluffy white parachute.
Last Thursday’s wind carried them away to a new home.
Tonight’s snow will cover them.
(photo by Kate St. John)
This week’s tree is easy to identify by its twig.
The sugar maple (Acer saccharum) is a common tree in northeastern North America, prized for its wood, its brilliant fall foliage and its sap for maple syrup in the spring.
Like the white ash, the sugar maple is one of the few trees with opposite leaf buds. If you look closely you’ll see that each pair of buds is rotated about 180 degrees from the previous set. This keeps the tree in balance as the buds eventually become branches.
Sugar maple twigs are brown and slender and the leaf buds are brown and very pointy. Test the tip of a bud with your finger and you’ll find it’s almost sharp!
A good hint for remembering the tree is to realize that the buds resemble upside down ice cream sugar cones. “Sugar cones” on sugar maples.
Many trees are easy to identify by their bark but the sugar maple is not one of them. The bark on young trees is stone-gray and smooth as shown below…
…but the bark on mature trees becomes furrowed with large flat scales that seem to vertically peel off the tree. This makes for a lot of variation and can be quite confusing. When I finally learned to identify sugar maple bark I called it “the bark that looks like nothing else.” Not easy to explain.
If I’m stumped by the bark on a tall tree I always have one more trick up my sleeve. I use my binoculars to examine the twigs.
Are the buds opposite, brown and pointed like sugar cones? Sugar maple!
(photos by Kate St. John)
Just after Thanksgiving the tree cutters visited my neighborhood. Hired by Duquesne Light, they trimmed or cut down every tree they found near the electric lines at Magee Field.
After they were gone I went to check the damage. Did they cut down the honeylocusts whose pictures I’d taken the week before?
One look at the trunk of a honeylocust (Gleditsia triacanthos) and you know right away you don’t want to touch it. The tree is protected by huge clusters of branching 3-inch-long thorns quite capable of impaling your hand.
The thorns are diagnostic. No other tree in Pennsylvania has them(*).
The twigs are distinctive, too. They’re stout, zig-zagged and tapered but there’s no need to remember that because the thorns stand out. They’re reddish-brown, thick and branching just like the thorns on the trunk. Hawthorn trees have thorns but nothing like this. Theirs are long, slender and unbranched.
Here’s a picture of the twig showing the tip of my thumb while I gingerly hold it against the paper. The longest thorn is as long as my thumb!
So did the tree cutters take down the honeylocusts?
No. Of course not!
(photos by Kate St. John)
* p.s. The closely related waterlocust has similar thorns but doesn’t grow in Pennsylvania.
Here’s a tree that will soon disappear from western Pennsylvania, a victim of the emerald ash borers that arrived here in 2007.
White ash (Fraxinus americana) is easily identified by its twig with the chocolate-brown bud. The twig is stout, the leaf buds are opposite each other, the leaf scar is a horseshoe shape under each leaf bud, and all the buds are chocolate brown. (Click here for definitions of twig anatomy.)
It’s easy to find these buds in our area. There are many white ash seedlings now because the trees have put out a lot of seed while they’re under attack.
Opposite leaf buds are a good marker for the ash because most trees have alternate leaves. The main species with opposites are maples, ashes, buckeyes and dogwoods. I learned to remember opposite leaves with the acronym MAB DOG (Maple, Ash, Buckeye and Dogwood).
White ash bark is distinctive too. Its deeply ridged and the ridges join to form long diamond shapes as shown below.
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Unfortunately, larvae of the emerald ash borer kill the tree by tunneling under the bark and damaging the phloem and xylum. Often this causes the ridges to slowly separate from the bark. Woodpeckers hear the larvae (amazing!) and chip away at the ridges to get at the bugs. The result is that a dying tree has pale patches where the ridges fell off. Infected trees try to survive by sending out sprouts near the ground. You can see both effects on the trunk below.
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If you examine the chipped bark closely you may find the D-shaped exit hole of the emerald ash borer. (Thanks to Dianne Machesney for this photo.).
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Learn the white ash now. Sadly, it won’t be with us much longer.
(photos by Kate St. John, except for the one noted by Dianne Machesney)
Today is the first entry in this winter’s Wednesday tree series.
Though I mentioned we would identify trees by their twigs I can’t resist starting the series with a tree that’s really easy to identify by its bark.
This is the Common Hackberry (Celtis occidentalis), a member of the Hemp family. It produces small berries that ripen in autumn. Some berries fall to the ground, others persist on the tree into the winter and provide a good food source for birds.
For me the easiest way to identify young hackberry trees is by their bark. (Bark is at eye level!)
Hackberry bark looks as if someone glued lumpy pie-crust ridges onto the originally smooth gray surface. You can see these odd ridges in the photo above.
A second very distinctive trait is the witch’s broom, easy to see when the leaves are off the trees. Not all hackberries have these bundles of malformed twigs but when you see them in combination with the lumpy bark you can be sure you’ve found a hackberry.
Here’s a close-up of a witch’s broom. Not only do the twigs clump at one spot but there are woody lumps at their base.
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As the trees mature the pie-crust lumps grow farther apart and sometimes look as if they’ll peel off the trunk.
Hackberries are easy to find in Schenley Park, especially near the Greenfield Bridge.
(three photos by Kate St. John. Photo labeled UGA5188076 is by Whitney Cranshaw, Colorado State University from Bugwood.org )
On my walks through Schenley Park I’ve started to notice the trees again. Not that they’ve been missing — far from it! — but ever since the songbirds arrived last spring the trees were mere bird accessories, places for birds to find food, nest and perch.
Now the migratory songbirds have left and the deciduous trees have gone through a great transformation. They’ve dropped their leaves and seeds and stripped down to trunks and twigs. They’re easier to see and they’re easier to identify.
Back in the 1990’s I took a class on winter tree identification at Chatham University’s Rachel Carson Institute where I learned that twigs and bark tell you almost all you need to know to identify a species. In class we used the booklet pictured above, the Winter Tree Finder by May Thielgard Watts and Tom Watts. It’s easy to carry and contains a step by step key for identifying twigs, much like Newcombs Wildflower Guide does for flowers.
In late October when I noticed the trees again, I got excited and took my Winter Tree Finder to Schenley Park. Soon I began taking pictures of bark and twigs. It didn’t take long before I’d dreamed up a Wednesday series on Winter Trees.
Today is the first entry but it’s just an introduction. Before I start showing you the trees next week you may want to do two things:
Next Wednesday I’ll show you the first tree in the series, all of which grow in southwestern Pennsylvania. I know they do because I found all of them in Schenley Park.
(Cover of Winter Tree Finder from Amazon.com. Image of twig anatomy linked from Clemson University’s Familiar Trees of South Carolina)
Last Saturday my husband and I participated in our neighborhood fall cleanup. At Magee Field this involved a lot of clambering on the hillsides to collect beer cans and water bottles that people had “thrown away” in the woods. Volunteers collected 14 large bags of garbage.
After the cleanup I threw our clothes in the wash but when I pulled them from the dryer I found an unwelcome surprise. My socks had collected burdock and the laundry had broken it up and redistributed it as tiny hooks on the bath towels. I spent half an hour pulling the hooks off one by one.
Lesser burdock (Arctium minus) is a biennial plant in the Aster family. Native to Europe, it’s now invasive in North America and so successful that USDA lists it as invasive in Greenland.
Burdock spreads easily by hitchhiking on mammals. Its purple flowers bloom in late summer inside bracts covered with tiny hooks. In the fall the flowers dry and the bracts tighten around the seeds (shown above). Now the ball is ready to grab fur, skin or clothing and transport the seeds to a new location.
The hooks are so fascinating that they led to the invention of Velcro.
In 1941 Swiss inventor George de Mestral went out hunting with his dog and they both came back with burdock stuck to them. De Mestral studied the hooks and saw the possibilities for a reusable fastener. He experimented with various materials and found nylon and polyester to be the best. His invention was patented in 1955 and ultimately grew into Velcro USA Inc, based in Manchester, New Hampshire.
Velcro didn’t catch on at first because it seemed stiff and unwieldy on clothing, but after NASA used it on astronauts’ space suits, skiers saw its value and now the rest of us use it too.
It pays to observe nature. In de Mestral’s case it led to great things. As he once told Velcro executives, “If any of your employees ask for a two-week holiday to go hunting, say yes.”
(photo by Dianne Machesney)