Archive for the 'Winter Weeds & 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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Nov 13 2012

The Trees With Leaves Are…

At this point in November most of the trees in western Pennsylvania have lost their leaves.  There are exceptions and you’re likely to find them in parks and residential areas.

Yesterday morning I took this picture at the big bend on Greenfield Road in Schenley Park.  If you didn’t know it was a recent photo you’d think it was taken in early October at the peak of autumn color.

These are Norway maples whose native range in Europe extends further north than Pittsburgh.  Our short November days are the same length as those they experience in October back home.  For instance, the sun will be up for exactly 10 hours today in western Pennsylvania.  That’s the day length in mid October in Scandinavia.

Right now our native trees are bare or retain just a few leaves at the top (tulip trees) or brittle brown leaves overall (oaks and beeches).

The non-natives plants are out of synch and late November is the one time of year when you can easily see them across the landscape.

Make an effort to identify the trees and plants with green or colorful leaves and you’ll find that they’re probably imported.

 

(photo by Kate St. John)

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Nov 06 2012

Since 1600


When Northern Europe was deforested many centuries ago only one native pine survived:  the Scots pine (Pinus sylvestris).

Beginning in the 1600’s when Europeans came to North America, they brought the Scots pine with them.  No matter that eastern North America already had more than a dozen native pine species.  They planted this one anyway.

Since then the Scots pine has had a checkered history on this continent.  In some places it became invasive, in others it was stunted by poor growing conditions.  During my childhood it was a popular Christmas tree.

Nowadays it grows naturally from Maine to Wisconsin to West Virginia.  You’ll recognize it by its twisted trunk, rusty red bark near the top of the tree, and two needles per bundle.

The cones are fun to collect because they aren’t prickly.  If you live within the Scots pine’s range, these are easy to find.

(photo by Didier Descouens, Museum of Toulouse France, from Wikimedia Commons. Click on the image to see the original)

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Nov 04 2012

The Trees Are Bare?

Lots of the trees are bare now that Hurricane Sandy came through Pennsylvania.  But not everywhere.

Here, the trees look wintry in Schenley Park on November 1.

But just around the corner the view from Panther Hollow Bridge is mixed.  The large sycamore is bare — see the ghostly white bark? — but the red oaks still show off their russet tones.  (These pictures are dark because it was raining. It rained every day last week.)

 

Elsewhere in Pennsylvania, winter comes earlier.

Here’s a picture from the Quehanna Wild Area taken on October 13.  Three weeks ago most of the trees were already bare in this part of Clearfield County.

What’s it like where you live?

(photos by Kate St. John)

 

 

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Oct 14 2012

Ash Leaves

This is one of the things I’m going to miss when all the ash trees have died.

In autumn ash leaves turn yellow, orange and lavender.  Often, all of the colors are on the same leaf.  No other tree is quite as beautiful.

Fall won’t look the same when the ashes are gone.

(photo of ash leaves in Schenley Park by Kate St. John)

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Oct 09 2012

How Stakes Hurt Trees


Every day on my way to work I pass this unusual tree in Schenley Park.  It was planted with care, probably more than 40 years ago, when stakes were provided to stabilize the young tree.

But the stakes were never removed.  The tree grew and grew.  The trunk had nowhere to go except outward.  Slowly it engulfed the stakes.

Now this tree’s in a world of hurt.  The rubber guide and wires disappeared long ago.  The stake on the right is still outside the trunk but only a short length of wire is visible (below).

 

The other stake is completely surrounded.  Its top is inside the trunk.

And now the stakes can never be removed.  Though they’ve created a weakness in the trunk, they’re the only support the tree has at that spot so they have to stay.  The damage is done.

It’s too late to save this tree, but you can help others.  Examine staked trees to make sure the guides are not girdling the trunk.  Remove the stakes 1 to 2 years after planting.

For more information see Bartlett’s plant health guide for newly planted trees.

(photos by Kate St. John)

 

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Mar 14 2012

Winter Trees: Speckled Alder


Spring is coming fast but there are still a couple of weeks before the tree buds open.  This tree, however, will bloom very soon so we’ll need to identify it now.

Speckled Alder (Alnus incana) is a shrub-like tree in the birch family that grows in wet places at streams, lakes and wetlands.  In winter its branches are distinctive because they carry two kinds of buds with last year’s fruit.

The inch-long male catkins are reddish in winter.  They begin to turn yellow in March just before they bloom into long, yellow pollen flowers.

The female flower buds are small and drooping just ahead of the catkins on the branch.  They look like tiny unopened versions of the seed-bearing cones they’ll become.

The cones are present, too.  Half an inch long they’re last year’s fruit.  All three are visible in the photo above.  The male and female flowers are shown below.

 

Speckled Alder gets its name from the whitish lenticels that speckle its dark bark.  With all these points of interest we hardly notice the small reddish leaf buds.

As you explore stream banks and lake sides for signs of spring, keep an eye out for Speckled Alder.

Someone* told me it carries the past (cones), present (male catkins) and future (female buds) on each branch.

(photo by Marcy Cunkelman)

 

(*) Was it Esther Allen who said this tree is Past, Present and Future?

 

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Mar 07 2012

Winter Trees: Red Maple

For some of the red maples in Schenley Park, winter is over.  They’re already blooming.

Red maples (Acer rubrum) are one of the earliest trees to flower in the spring, producing red female flowers and yellowish male flowers.  The male flowers are actually red but appear yellow from a distance because the yellow stamens extend beyond the red petals.

Shown above are the female flowers.  Look closely and you can see the tiny wings of the fruit that will form from each flower.

Weeks ago I photographed the winter buds which, like all maples, are opposite on the stem.  The red buds are globular, the bud scales are rounded.  Here’s a close-up of what the buds looked like when they were closed.

Nearly everything about the red maple is red — the buds, twigs, flowers, fruit (before it dries), leaf stems and fall leaves.  Red maples are so beautiful in autumn that they are often planted in cities and parks.

Red maple bark is not as easy to identify.  It’s smooth on young trees and rough on old ones with vertical cracks that peel up a bit.  Here’s a look at the bark that proves it’s easier to identify this tree by its buds.

 

Today and tomorrow we’ll have temperatures in the 60s and more of the red maples will bloom.  Use binoculars to see the flowers.

Soon the Winter Tree series will end because the trees will have leaves.

(Bud and bark photos by Kate St. John. Red maple flowers’ photo from Wikimedia Commons.  Click on the flowers’ photo to see the original)

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Feb 29 2012

Winter Trees: Ailanthus

Today’s tree is a noxious weed that goes by many names:  Ailanthus, Tree-of-heaven, Chinese Sumac, Stink Tree and The Tree From Hell.  Some people call it simply “Sumac” but that’s one thing it is not.  Though its leaves are similar, it’s not related to sumac.

Ailanthus altissima is native to China and Taiwan, first brought to North America as seed in 1784.  In the 1800’s it was planted as a street tree but quickly became invasive.  Nowadays no one will buy this tree.  People spend money trying to get rid of it.

It earned its name Stink Tree because the male flowers smell bad, something between cat pee and rotting cashews.  When ailanthus was planted as an ornamental, the nurseries sold only female trees.

Though ailanthus typically lives only 50 years, it grows anywhere humans have abused air, land or water.  It doesn’t flinch in the face of sulfur dioxide, mercury and ozone.  (It actually absorbs sulfur dioxide in its leaves.)  It can grow with water polluted by acid mine drainage, in soil low in phosphorous and high in salinity.  The only thing it doesn’t tolerate is dense shade.  This adds up to a very successful roadside weed that thrives in the face of air pollution and road salt.

Ailanthus is prolific and hardy, able to grow from its huge seed production or from root stock.  The roots sprout so well that it’s almost impossible to eradicate the tree.  And it grows really fast!  3.3 to 6.6 feet per year in its first four years.  Not only that, it produces a chemical that kills other species.  Experiments with ailanthus extract demonstrated that it’s an effective herbicide against almost every other seedling.

With all these disadvantages, it pays to know what ailanthus looks like.  It’s easy to identify in winter by the stout twig, pictured above, that ends abruptly without tapering.  Its orange-brown twig is as big around as your finger with large, heart-shaped, alternate leaf scars and a small bud in the notch of each heart.

Ailanthus bark is very smooth with small pits on younger trees (shown at left) and interlacing ridges on older trees (shown at right).  Learn the twig first, then you’ll remember the bark.

So, what good can be said about this tree?

It will be the last tree standing when the world comes to an end  …  and its hardiness gave it a brief literary and stage career as “The Tree” in A Tree Grows in Brooklyn.

(photos by Kate St. John)

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Feb 22 2012

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.)

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