Archive for the 'Trees' Category

Oct 03 2013

Acorns Are Connected

Acorns of northern red oak (photo from Wikimedia Commons)

Stop and listen in Schenley Park right now and you’ll hear acorns falling, blue jays calling and squirrels scurrying.   It looks like a bumper crop for acorns in Pittsburgh. (*see p.s.)

Right now the red oaks are putting on a show.  Acorns in the white oak group mature in the same year they flower.  Acorns in the red oak group take two years to mature so those falling now were formed in the hot spring and summer of 2012, influenced by spring precipitation, summer temperatures and the date of the last killing frost.

Though we (usually*) don’t eat them, acorns are a key link in the woodland food web.  They’re so popular that oaks have evolved an abundance-scarcity strategy to throw off their consumers.  In some years acorns are so abundant that the crop overwhelms the acorn-eaters.  In other years they’re so scarce the consumers go hungry.  To further confuse things the oak groups cycle on different schedules: white oaks have a bumper crop in 4-10 years, red oaks on a 3-4 year basis.

Who eats these acorns?  Squirrels and chipmunks are the obvious consumers but plenty of other species depend on them including white-footed and deer mice, blue jays, red-headed woodpeckers and wild turkeys.  Deer, ruffed grouse, bears, mallards and wood ducks eat acorns, too.

The bumper crops have a ripple effect.  A 24-year study, headed by Clotfelter and Pedersen in the southern Appalachian Mountains of Virginia, followed the effects of acorn crops on rodent abundance, raptor abundance and the nesting success of ground-nesting birds.  They focused on white-footed mice, deer mice and dark-eyed juncoes and found these amazing acorn effects:

  • The population of white-footed and deer mice increases in the year after a bumper crop of acorns.
  • Rodents attract predators so the raptor population increases.
  • Too many rodents and raptors causes junco nest failure due to predation on eggs, nestlings and birds.
  • Mice eat gypsy moths so the gypsy moth population drops.
  • The number of ticks increases as white-footed mice and deer increase.

And then, this information from PLOS links acorns to Lyme disease:  Lyme disease increases predictably two years after an acorn bumper crop because white-footed mice are a main reservoir for the Borrelia burgdorferi bacteria.

Don’t blame the acorns.

Everything is connected to everything else.

 

(photo from Wikimedia Commons. Click on the image to see the original)

*p.s. Is this a bumper crop year?  I wrote about acorns because I’ve been dodging them in Schenley Park as they fall, but not all the trees are prolific.  Hmm….

*”We don’t usually eat acorns”:   Well, we can … after a lot of work.  See kc’s comment!

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Sep 04 2013

Three Sumacs And Two Imposters

Published by under Plants,Trees

Sumac fruit (photo by Kate St. John)

In July I took photos of sumacs along the Montour Trail but didn’t identify the species and assumed these first two were staghorn sumac.  Wrong!

As I started to write this article I examined the photos and noticed a big difference between them.  The red fruit spike above is fuzzy.  The one below is smooth.   Not only that, you can see that the stems on the top one are also fuzzy but the stems below are smooth.

Fruit of smooth sumac (photo by Kate St. John)

In southwestern Pennsylvania we have three common sumac species that bear pointed red fruit clusters:

  • Staghorn sumac (Rhus typhina), at top, has fuzzy fruit and stems and is named “staghorn” because the fuzzy fruit spike resembles a stag’s horn in velvet.
  • Smooth sumac (Rhus glabra), above, is smooth just like its name.
  • Shining sumac (Rhus copallina) is easily identified by its winged stems.

I haven’t seen Shining Sumac lately so here’s a photo from Wikimedia Commons.  See how the stem has wings (like wingstem) between the leaflets?

Leaves and flower of Shining Sumac (photo from Wikimedia Commons)

 

There are two more plants we call “sumac” whose leaves resemble these plants but they aren’t in the genus Rhus:

  • Poison-sumac (Toxicodendron vernix) is in the cashew family (as is Rhus) but it’s closely related to poison ivy and causes the same rash.  Its stems are smooth, like smooth sumac, but its flowers and fruit are not in dense spikes.  Fortunately poison sumac only grows in swamps and bogs so you’d have to go out of your way to touch it.  Click here for a photo.
  • And finally there’s a plant we call “sumac” which isn’t related at all.  Tree of Heaven (Ailanthus altissima) is an invasive tree from China with compound leaves that resemble sumac.  However its leaflets are notched, especially at the base, and the tree produces seeds instead of a fruit spike.  Notice the notches on the leaflets and the heavy cascade of seeds in this Wikimedia photo.   This is NOT sumac.   It grows anywhere, even in abandoned parking lots.

Ailanthus leaves and seeds (photo from Wikimedia Commons)

 

Three real Rhus sumacs and two imposters.

(photos by Kate St. John except where noted.  Click on the Wikimedia photos to see their originals)

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Aug 01 2013

Plant a Shrub, Start a Fight

Published by under Plants,Trees

Leylandii, Roman Bank, Holbeach Hurn (photo from Wikimedia Commons)

The tall square hedge in this photo is the species that launched 17,000 complaints.  It’s also been blamed for the decline of the house sparrow in the UK.

When a tree is implicated in the decline of a bird I’m compelled to find out why.

Leyland cypresses (Leylandii) are an accidental hybrid of the Nootka and Monterey cypresses (of the Pacific Northwest), first discovered in the gardens of Leighton Hall in northern Wales in 1888.  The hybrid is sterile but can be propagated by cuttings. It became popular in UK landscaping because the foliage is so thick it provides privacy from neighbors.

Leylandii are huge trees that grow three feet per year and can reach 130 feet tall, but they’re used as hedges and therein lies the problem.

When planted as cute little “shrubs,” people imagine their Leylandii will look like this…

Well-trimmed Leylandii in Chilwell (photo from Wikimedia Commons)

…but that tidy look takes constant trimming.  Instead the hedgerow turns into this…

Leylandii hedgerow (photo from Wikimedia Commons)

…and can engulf nearby buildings.

For instance, Snarestone Pumping Station was visible from the road in 1994 before Leylandii were planted at the perimeter.  By 2010 only the top of the smokestack can be seen above the trees.  (Notice the little red car at the right side of the right hand photo.  These trees are huge!)

Snarestone pumping station before and after Leylandii, 1994 & 2010 (photos from Wikimedia Commons)

Leylandii block views and create very dense shade.  Neighbors ask owners to trim them.  The disputes begin.

By 2005 there were 17,000 disputes, prompting Parliament to pass an “anti-social” law to settle them.  When neighbors object to Leylandii they must first try to settle the dispute privately.  If this fails they can ask local Council to intervene and pay a fee to begin.  Council can rule that the trees be trimmed to 2 meters (6 feet).  Failure to comply can result in a £1000 fine.

Here’s an example of a dispute in Plymouth, complete with a video that shows the neighborhood.  The trees completely obscure the owner’s house.  Notice that the neighborhood has no plantings for birds either.

How do house sparrows figure into this?  House sparrow population studies have shown they thrive where there are deciduous trees, not evergreens.  House sparrows are declining.  Leylandii are oppressive evergreens.  Voilà!

(photos of Leylandii from Wikimedia Commons.  Click on the images to see the originals)

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Jul 30 2013

Oak Wilt Strikes Again

Published by under Schenley Park,Trees

Oak wilt in Schenley Park, 5 July 2013 (photo by Kate St. John)

I love trees so much that I jump at the chance to learn more about them.

Back in February 2011 I learned about the threats facing 60% of our city park trees when the Pittsburgh Parks Conservancy presented a public event called Preserving Pittsburgh’s Trees: Action and Recovery.   I was already familiar with emerald ash borer since I first saw it in Schenley in May 2010 but I learned about something I’d never seen before: oak wilt.

While Schenley Park had been coping with the death of all its ash trees, the other three big parks — Frick, Highland and Riverview — had experienced oak wilt as well.

Oak wilt is caused by a fungus that doesn’t spread easily but can kill a tree in 30 days.  The fungus travels in the oak’s vascular system and when the tree detects it it blocks those vessels.  The blockage kills the tree. It’s the arboreal equivalent of a stroke.  Watch the 13 minute video here to see how this happens.

After the conference I began to watch Schenley’s oaks with new interest.  Two years passed.  Early this month I could tell something wasn’t right at Prospect Circle.  I emailed this and other photos to Phil Gruszka, Director of Park Management and Maintenance at the Pittsburgh Parks Conservancy, and he confirmed that oak wilt had struck again.  He also started the ball rolling to eradicate it.

Fortunately the fungus spreads slowly and that’s the key to stopping it.  It’s either carried into an open wound by sap-eating beetles (this is harder than you think) or it travels from oak to oak via root grafts.  Amazingly, the roots of adjacent oaks graft to each other when they touch underground.  In a pure oak stand they become one huge vascular system.

There is no cure but future deaths can be prevented by cutting down the affected trees, trenching the perimeter to prevent uninfected roots from entering the danger zone, and medically treating the oaks just outside the perimeter.

In the not too distant future a large patch of dead and dying oaks will be chopped down at Prospect Circle.  This will look ugly at first but will save all the other beautiful oaks along the road and hillside.

For more information about oak wilt, read these Pittsburgh Parks Conservancy blogs about the episode in our parks in 2010:

 

(photo of the oak wilt trees in Schenley Park, July 2013, by Kate St. John)

 

p.s. Learn more about the trees in our city parks at this link on the Pittsburgh Parks Conservancy website.

UPDATE on 18 October 2013 from the Pittsburgh Parks Conservancy –> click here.

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Jul 23 2013

These Are Not Pine Cones

Bagworm moth caterpillars on cedar tree (photo by Stephen Tirone)

When Steve Tirone learned the identity of these pine cone look-alikes he had his work cut out for him.

Early this month he sent me this photo (below) and asked:  “Any idea what this is? I had a few on my house last year. They are near my cedar tree.”

Bagworm moth caterpillar (photo by Steve Tirone)

I emailed Monica Miller who replied: bagworm moth caterpillar.

Bagworms adorn themselves with disguising vegetation that eventually becomes their pupating bag.  Until then they chow down on their favorite foods.

Steve looked closely at his cedar tree and discovered it was covered in caterpillars that were eating it alive.  No wonder it looked sick!  He also learned that pesticides don’t work on these bag-covered bugs.  The only way save his tree was to pull off each one by hand, as in…

[I picked them off] for 2 hours today, along with chopping out large parts of the tree.  Ugly work, ugly results, and there are still tons left. Every time I go by the tree I say “How did I miss that one, and that one?”  Easy, because they look just like pine cones!

If any remain on the tree, what will happen next?

Monica did not specify the bagworm species — there are over 1,000 of them worldwide — but I’ll tell you the story of the evergreen bagworm moth (Thyridopteryx ephemeraeformis (Haworth)) because it’s a particular pest of cedars (Thuja occidentalis also called arborvitae).

From May to August the caterpillars eat and mature through seven instars.  In August the mature caterpillars prepare to pupate by hanging their bags from host plants by a strong silken thread.  Then they turn around inside the bag to face downward.

Four weeks later, in September and early October, the males emerge.  They’re about an inch long and are easy to overlook because they’re small and black, about an inch long.  They eat nothing.

Bagworm moth (photo by Mark Dreiling, Retired, Bugwood.org)

The females never emerge.  They’re wingless, legless and have no functioning mouth parts.  They’re just a bag of eggs and pheromones waiting for a male to land on their bag and mate with them.

As soon as the females have mated they shut off their pheromones and lay 500-1,000 eggs inside the pupal sack inside the bag.  They live a couple of weeks, crawl out of the bag to die or become mummified inside.  The males are long gone, having died within a day or two of their emergence.

Over the winter the bag hangs on the tree with 500 to 1,000 potential caterpillars waiting to hatch next spring.

If you pull these bags off your cedars before April you’ll save your trees a lot trouble.

moth_bagworms_in_cedar_1860096_rsz_bugwoodTwo bagworm moths overwintering on a cedar (photo by Lacy L. Hyche, Auburn Univ, Bugwood.org)

For more information see this fact sheet from Penn State.

 

(first two photos by Stephen Tirone.  Moth photo (5462023) by Lacy L. Hyche, Auburn University via bugwood.org.  Bags photo (UGA1860096) by Mark Dreiling via bugwood.org)

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Jun 16 2013

Mulberries Underfoot

Published by under Trees

White mulberry fruit (photo by Kate St. John)

It’s been mulberry season for two weeks now.  In our house it means we take off our shoes.

White mulberries (Morus alba) were imported from China in colonial times in hopes of starting a silk-making industry.  If you import the silkworms and their host, of course you’ll get silk.  Not!  The silkworms died but the trees did not.  They now hybridize with native red mulberry and are considered invasive.

On the plus side, white mulberries produce a lot of fruit for people and birds.  We make the fruit into jams and jellies, the birds lead their fledglings to the trees where they safely sit and eat.

The problem is the fruit is prolific and falls readily from the trees.  One tree in particular shades the sidewalk on our path through Magee Field to Schenley Park.  Right now the sidewalk looks like this.

Sidewalk covered in white mulberries (photo by Kate St. John)

The fruit is unavoidable even if you walk in the grass.  The berries squish underfoot (quite unpleasant!) and smash into the ridges on the bottoms of our shoes.  The juice stains the carpet if you don’t clean it immediately.

So we’ve adopted the Japanese in-house shoe tradition.  In mulberry season we take off our shoes.

(photos by Kate St. John)

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Jun 08 2013

Success Through Landscaping

Published by under Trees

When most other trees have already set seed, northern catalpas put on their show in June.  Right now they’re flowering in Pittsburgh.

Northern catalpas (Catalpa speciosa) are not only late to flower but they’re slow to leaf out, retaining that fresh green color of early spring much later than other trees.  Their flowers become long bean pods in the fall.

Though native to North America, catalpas were uncommon until landscapers fell in love with them.  Their original range was in wet soil along streams, lake shores and swamp margins.  Some sources say northern catalpas were limited to a small area near the confluence of the Ohio and Mississippi Rivers.

But their trumpet flowers turned the tide.  Landscapers planted varieties that could grow almost anywhere and now they do.  Catalpas escaped cultivation and expanded their range across the eastern U.S., from Massachusetts to Kansas, from Wisconsin to South Carolina.

Catalpas are now so successful that they sprout up in waste places and along roadsides, a dramatic success thanks to landscaping.

 

(photo by Kate St. John)

 

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Apr 18 2013

Putting On The Green

Ohio buckeye leafing out (photo by Kate St. John)
This week the trees in Pittsburgh are putting on the green.

The flank of Mt. Washington is my favorite place to see it.  All winter the hillside is a flat brown color without the look of individual trees but now each leafing tree shows up as a pale green crown.  Some are white with flowers.

This appearance is ephemeral.  Soon the leaves will be large and shady and the hillside will look uniformly green.  So now while the trees are changing so fast here’s a close look at what they’ve been up to.

Above, in Schenley Park an Ohio buckeye leafs out.  Below at a later stage the flower buds emerge. (*see the Comments for discussion on this tree)
Ohio buckeye flower buds (photo by Kate St. John)

 

The bitternut hickory is not so quick but its mustard yellow bud has begun a leaf.

Bitternut hickory bud opening (photo by Kate St. John)

 

The pignut hickory’s end bud is furry, shiny and enormous.
Pignut hickory bud (photo by Kate St. John)

 

These catkins look like caterpillars.
(Dark bark, perhaps a sweet birch. Do you know what tree this is?)
Catkins that look like caterpillars (photo by Kate St. John)

 

And the crown jewels are the magnolias, native to Asia.  This is a star magnolia.  Wow!
Star magnolia blooming (photo by Kate St. John)

(photos by Kate St. John)

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Nov 28 2012

Why Not Here?

Published by under Trees

When I travel east on the Pennsylvania Turnpike I’m always amazed when I reach Bedford County and see the landscape dotted with trees like this one.  They grow like weeds east of the Alleghenies, but not in western Pennsylvania.

When I saw them last weekend I said to myself, “Cedars.  Why don’t we have cedars at home?” and I set myself to find out.

My first surprise was that this tree is not a cedar at all.  It’s in the cypress family and it’s a juniper (Juniperus virginiana) whose common name, Eastern Redcedar, is probably a reference to its aromatic wood.

The second surprise — for those of us who live outside their range — is that junipers are very hardy and grow under a wide variety of conditions.  They’re pioneers in disturbed or damaged soil, especially in old fields and along roadsides, and they live a long time — up to 850 years.

To identify a juniper, look for a small evergreen with reddish-brown bark that peels off in strips.  The young trees have sharp needle-like leaves, the mature ones have scale-like leaves.  (This is hard to describe; see picture below).

The juniper’s aromatic wood is used to line cedar chests and keep moths away.  Its bluish waxy-looking berries are a favorite food of many mammals and birds, especially cedar waxwings, eastern bluebirds and wild turkeys.  People like the berries too.  We use those of Juniperus communis to flavor gin.

 

The first picture is what junipers look like near the turnpike in Bedford County, shaped like lollipops because they’re browsed by the overabundant deer. The picture below shows their normal shape when the deer population is in balance. I suppose we could use junipers as a deer population gauge… but they don’t grow here in Pittsburgh.

 

Junipers grow wild in the far southwest corner of Pennsylvania, in Ohio, West Virginia, Maryland, the Appalachians, and eastern Pennsylvania.  They grow from southern Maine to Georgia, from Delaware to Kansas (see map).  Why not on the Pittsburgh and Allegheny Plateaus?

I haven’t found the answer.  It’s still a mystery.

 

(photo credits:  Deer-browsed juniper by Paul Bolstad, University of Minnesota, Bugwood.org.  Juniper berries by D.E.Herman, USDA. Eastern juniper at Sandy Hook, NJ by Miguel Vieira on Wikimedia Commons. Click on the photos to see the originals.)

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Nov 21 2012

Why So Many Robins?

Published by under Bird Behavior,Trees

Why are there so many robins in Pittsburgh right now?  Food.

What are they eating?  You’re looking at it.

These are Bradford callery pears, the fruit of a popular small street tree that has pretty white flowers in early spring.

This particular cluster is from a row of trees next to the Pittsburgh Board of Education on Bellefield Avenue but I’ve found Bradford pears at Carnegie Mellon, at Pitt, on neighborhood streets, in mall parking lots … they’re everywhere.

And they’re imported. Callery pears are normally thorny trees.  Native to China they were first brought to the U.S. in 1918 as an experiment in producing rootstock for pear orchards, but that didn’t work out.  Instead, one of the experimental trees grew without thorns, was recognized for its ornamental value and became the “Bradford” cultivar.  By 1982 Bradford callery pears were the second most popular landscape tree in the U.S.

As usual with non-natives, they are easy to point out in late November because they still retain their leaves.  Before they fall the leaves turn yellow, orange and then deep red, another reason for the tree’s ornamental value.  In spring the flowers bloom earlier than our native trees.  (I happen to think the flowers smell bad but most people don’t notice it.)

Since their introduction, callery pears have become naturalized and in some places invasive.  It’s easy to see how their seeds spread when you watch a flock of birds feasting on them.  This year the fruit is especially prolific and so are the robins and starlings.

As soon as the fruit is gone and the ground is covered with snow, the robins will go.  Until then, it’s a party.

(photo by Kate St. John)

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