Last weekend I found these twisted trees in Moraine State Park.
It’s unusual to find trees like this — even more unusual when they’re two different species.
A black cherry (left at base) and a red oak (right at base) germinated next to each other. At the ground their trunks touched and melded. As they grew they twisted around each other.
Amazing.
(photo by Kate St. John)
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Last spring the hemlock woolly adelgid (HWA) reached Cooks Forest, scary news for the old-growth eastern hemlocks there.
The pest is easy to recognize by its white egg sacs that cling to the underside of the branches. They kill hemlocks by sucking the juice out of the needles. Infected trees look gray-green instead of deep green and, under a heavy infestation like the one shown above, can die in only four years. This is sad anywhere but especially unfortunate in Cooks Forest where the old growth hemlocks are over 300 years old.
It has taken a long time for the bug to reach Cooks Forest. HWA arrived from Asia in 1924 but moved very slowly across the eastern U.S. By 2007 it was present in 50% of the eastern hemlock’s range, unable to spread far northward because of harsh winters. Unfortunately our climate is warming so new adelgid territory opens up every year. (Notice on this NOAA plant hardiness map that the location of Cooks Forest warmed enough to change growing zones.)
HWA was first spotted in eastern Pennsylvania in 1967 but took about four decades to cross the Allegheny Front into western PA. Slowly, slowly it crept toward Cooks Forest. By 2010 it was in the vicinity. This year it was there.
Knowing the imminent danger DCNR has treated the area and the old growth trees. They use biological controls — Asian beetles that eat adelgids, though not enough of them — and soil or bole-injected insecticides on specific trees. The poisons are systemic, similar in concept to the insecticide treatments for emerald ash borer that kill or repel all insects. The treated trees will have fewer insects living on them. Will this make them less useful to birds?
The question hardly matters. Nature can’t produce a 300 year old hemlock as fast as the adelgids can destroy one. In the case of our oldest treasures our task is clear. Save these trees if we can.
For more information on the hemlock woolly adelgid, click here for DCNR’s report.
(photo via Wikimedia Commons by Nicholas A. Tonelli at Jacobsburg, Northampton County, PA. Click on the image to see the original)
p.s. Thanks to Kim Getz for alerting me to this news. Because of the adelgids activity cycle, DCNR treated the old-growth trees in May and again in October.
During a hike at Parker Dam State Park last year I noticed this hemlock, a tree on stilts.
Hemlocks have shallow root systems and can sprout easily in moist locations. Sometimes they sprout in the moss on top of a rock or stump and their roots follow the contour across the surface and become anchored in the earth nearby.
My guess is that this tree sprouted on a stump that decayed out from under it. The support disappeared after the hemlock’s root system was already established but the hemlock didn’t care. It sent down some new roots and just kept growing in place.
Hemlocks in this position are vulnerable in wind storms but this one is in the understory, surrounded and protected by many other trees.
It will probably surprise hikers on the Beaver Dam Trail for a long time to come.
(photo by Kate St. John)
3 October 2013
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:
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 if we put a lot of work into it. See kc’s comment!
3 September 2013
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.
In southwestern Pennsylvania we have three common sumac species that bear pointed red fruit clusters:
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?
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There are two more plants we call “sumac” whose leaves resemble these plants but they aren’t in the genus Rhus:
Three real Rhus sumacs and two imposters.
(photos by Kate St. John except where noted. Click on the Wikimedia photos to see their originals)
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 Nootka and Monterey cypresses, both from the Pacific Northwest. They hybridized on their own in the Leighton Hall gardens in northern Wales and were discovered 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. However, they’re used as hedges and therein lies the problem.
When people planted them as cute little shrubs, they thought their Leylandii might look like this.
But this tidiness requires constant trimming. Without it the hedgerow turns into this…
…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!)
Leylandii block views and create very dense shade. Neighbors ask owners to trim them. Then the fights 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. Interestingly, the neighborhood has no other trees and no plantings for birds.
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 in the U.K. Leylandii are oppressive evergreens. Voilà!
(photos from Wikimedia Commons. Click on the captions to see the originals)
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.
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.”
I emailed Monica Miller who replied, bagworm moth caterpillar.
Bagworms adorn themselves with disguising vegetation that eventually becomes their pupating bag. Until then bagworm caterpillars 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!
— Steve Tirone, July 2013
If any remain on the tree, what will happen next?
Monica did not specify the bagworm species — there are about 1,350 Psychidae worldwide — but I’ll tell you the story of the evergreen bagworm moth (Thyridopteryx ephemeraeformis (Haworth)) because it’s a particular pest of cedars (Juniperus virginiana) and arborvitae (Thuja occidentalis).
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. They eat nothing.
The females never emerge. They’re wingless, legless, have no eyes and 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, lay 500-1,000 eggs, then die and become mummified inside the bag. 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 from the carcass of their mother.
If you pull these bags off your cedars before they hatch in April you’ll save your trees a lot of trouble.
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)
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.
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)
8 June 2013
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)