Category Archives: Trees

Attacks Trees From Underground

9 May 2021

Have you ever seen these long black ropes draped on a fallen log? They were hidden under the bark before the tree died, and they’re the reason the tree died. These are mycelial cords or rhizomorphs of Armillaria, a genus of fungi that ultimately kills trees. It attacks the trees from underground.

Armillaria consists of 10 species which are easiest to identify by their mushrooms, the reproductive stage of the fungus. Honey mushrooms appear near the base of an infected tree but the spores rarely cause infection in other trees.

Fruiting bodies of Armillaria solidipes, Cook Forest, PA (photo from Wikimedia Commons)

Instead, Armillaria spreads by the rhizomorphs shown at top which travel only eight inches below the soil surface, advancing about 3.3 ft (1 m) per year. As they make contact with another tree they invade the roots and then the trunk. If a tree is already infected it will spread the fungus via root grafts.

Underground spread of armillaria disease (illustration from Wikimedia Commons, cropped)

Armillaria spreads so far and lives so long that a single Armillaria ostoyae in the Malheur National Forest in Oregon was found to be 2,400 years old and the largest living organism on earth.

As the infection takes hold, the fungus invades more deeply via white mycelium sheets that damage the roots or girdle the tree. Here a fallen black cherry reveals its cause of death.

Black cherry toppled near its base due to Armillaria, as seen by white sheets inside the wood, Schenley Park April 2017 (photo by Kate St. John)

Schenley Park is riddled with Armillaria but we have no hint that a tree is invaded until it topples, sometimes at the roots.

Trees are so stoic. No matter what attacks them, they just have to stand there and take it.

(photos by Kate St. John and from Wikimedia Commons)

Trees That Bleed Orange

Yellow-bellied sapsucker, 2011 (photo by Steve Gosser)

Yellow-bellied sapsuckers (Sphyrapicus varius) leave behind evidence of their visit when they pass through Pittsburgh on migration. In their search for food sapsuckers drill horizontal rows of holes on tree trunks and large branches, then lick the leaking sap and eat the insects attracted to it.

The trees cope as best they can with this unusual damage. Shagbark hickories (Carya ovata) grow puckered bark around the holes.

Shagbark hickory in Frick Park, horizontal rows are holes drilled by yellow-bellied sapsuckers (photo by Kate St. John)

Tuliptrees (Liriodendron) display clean holes.

This spring for the first time I’ve noticed trees bleeding orange sap after sapsuckers visit.

My best guess is that these are sweet birch (Betula lenta), also called black birch or cherry birch. Nothing says their sap turns orange, but a few facts tip the species scales for me.

  • New sweet birch leaves resemble cherry leaves. (I saw this yesterday)
  • The bark of older trees is dark and looks like plates.
  • Sap rises in sweet birch trees later and faster than it does in maples. (true)
  • We tap sweet birch trees and collect the sap to make birch beer. (Why is birch beer red?)
  • Deer don’t eat sweet birches so they’re more common now in Pennsylvania’s forests.

Have you seen any trees that bleed orange sap?

Do you happen to know if these are sweet birches?

(sapsucker photo by Steve Gosser, tree photos by Kate St. John)

UPDATE! Horticulturalist Sara Showers points out: “This looks like a phenomenon called “slime flux,” when leaking sap – a sugary food source! – is colonized by yeasts and other fungi. Here’s an article from Cornell about the phenomenon:

Meanwhile I’m becoming more convinced that the tree species is sweet birch based on its leaves and bark and abundant sap. No, the sap is not orange.

Spring Green

Spring green among the trees, Frick Park, 8 April 2021 (photo by Kate St. John)

10 April 2021

This week Pittsburgh’s sugar maples are clothed in spring green flowers while the oaks remain bare. Most trees bloom long before leaf out so their leaves won’t block the pollinators. These flowers take full advantage of the wind.

Sugar maple flowers, Schenley Park, 9 April 2021 (photo by Kate St. John)

Did your allergies kick in this week? The trees are throwing off lots of pollen with little rain to lay the dust.

Insect-pollinated flowers will follow soon. On 3 April pawpaw flowers (Asimina triloba) were still tiny buds in Schenley Park but by the time they bloom the stems will be long and flexible. The dark maroon fetid-smelling flowers will hang like bells to attract flies and beetles. Click here to see a pawpaw flower.

Pawpaw flower bud, Schenley Park, 3 April 2021 (photo by Kate St. John)

Eastern redbud flowers (Cercis canadensis) had not opened in Schenley as of 7 April, but they showed promise.

Redbuds, Schenley Park, 7 April 2021 (photo by Kate St. John)

Spring cress (Cardamine bulbosa) was blooming at Raccoon Wildflower Reserve on Easter Day.

Spring cress, Raccoon Wildflower Reserve, 4 April 2021 (photo by Kate St. John)

And Virginia bluebells (Mertensia virginica) were open in Schenley Park on 9 April.

Virginia bluebells, Schenley Park, 9 April 2021 (photo by Kate St. John)

This winter I noticed that when moss grows up the base of saplings it looks like leggings on the trees. At Raccoon Wildflower Reserve I found an entire group of saplings wearing mossy leggings. Click here to see the whole group. (Anyone know what this mossy phenomenon is?)

Mossy “leggings” on saplings, Raccoon Creek Wildflower Reserve, 4 April 2021 (photo by Kate St. John)

Spring green will continue in the coming weeks as tiny leaves pop open and more trees bloom.

(photos by Kate St. John)

Sap Rising and Other Signs of Spring

Sap dripping from a fallen oak, Schenley Park, 5 March 2021 (photo by Kate St. John)

6 March 2021

Flowers are pushing up their leaves and sap is rising in the trees.

On Friday the sap was rising so fast in this fallen red oak that it was dripping to the ground. The oak keeled over last year in Schenley Park leaving just one root in the ground. That root is still doing its job.

Sap rising in a fallen oak, Schenley Park, 5 March 2021 (photo by Kate St. John)

With temperatures this week above freezing during the day and below freezing at night I imagine it’s still maple sugaring time in the Laurel Highlands. Sugaring ends when the buds open. They haven’t opened yet in Schenley Park (below).

Sugar maple buds are not open, Schenley Park, 5 March 2021 (photo by Kate St. John)

Other trees have swelling buds.

Trees buds are swelling, Schenley Park, 5 March 2021 (photo by Kate St. John)

Below, silver maple (Acer saccharinum) buds were about to burst when a squirrel gnawed the stems and they fell to the ground. Do squirrels nip off the buds to get to the sap?

Silver maple buds attempted to open, Schenley Park, 5 March 2021 (photo by Kate St. John)

Meanwhile daffodil leaves are turning green in Schenley Park.

Daffodil leaves, Schenley Park, 5 March 2021 (photo by Kate St. John)

Tulip leaves emerged on a busy street in Oakland where the deer can’t get them. 🙂

Tulip leaves, Craig Street, 2 March 2021 (photo by Kate St. John)

And there is mud.

The snow melted all at once last weekend and the Monongahela River rose high, flooding the Mon Wharf. On Wednesday 3 March it was sunny and 60 degrees, a great time for a walk … but not here!

Monongahela River receding from flood stage, Pittsburgh South Side, 3 March 2021 (photo by Kate St. John)

When the river receded it left behind leafy debris and deep chocolate-pudding-like mud at South Side Riverfront Park. I tried to walk down there but I gave up before getting muddy. Others were not so careful. You can see deep footprints in the shade in the photo above (bottom left).

Closeup of debris and mud as Mon River recedes, 3 March 2021 (photo by Kate St. John)

It’s Mud Season in Pittsburgh!

(photos by Kate St. John)

Living Fossils in Pittsburgh

Base of a dawn redwood in front of Phipps Conservatory, Jan 2021 (photo by Kate St. John)

This month Tree Pittsburgh is featuring the dawn redwood as their Tree of the Month so I walked to Phipps Conservatory to see four of the living fossils. On the way I found a fifth near the Cathedral of Learning.

Dawn redwood on Pitt’s campus next to the Cathedral of Learning, Heinz Chapel in the background (photo by Kate St. John)

Endangered in the wild, the dawn redwood (Metasequoia glyptostroboides) is the only survivor of the genus Metasequoia from the age of the dinosaurs. It was thought to be extinct until a single living tree was discovered in 1941 in the village of Moudao in Hubei province, China.

The discovery happened in the nick of time. The tree would have gone extinct by now were it not for local protection and a seed-collecting expedition in 1947 that distributed seeds to ornamental gardens and arboretums around the world. Joe Stavish tells the story in Tree Pittsburgh’s video.

Tree of the Month: Dawn Redwood from Tree Pittsburgh on Vimeo.

Across the lawn the dawn redwoods at Phipps smile to other living fossils in Pittsburgh — the ginkgos that line Schenley Drive.

(photos by Kate St. John)

Planted in North America

23 December 2020

When the first Christmas trees were decorated in 16th century Germany the species of choice was the abundant Picea abies or Norway spruce. The Christmas tradition spread to North America and so did the tree. Nowadays you can find Norway spruces planted across the landscape of northeastern North America.

Some are in plantations.

Norway spruce plantation at Moraine State Park, Butler County, PA (photo by Kate St. John)
Norway spruces at Riverside Park in Cambridge, Ontario, Canada (photo by Ryan Hodnett via Flickr Creative Commons license)

Many stand alone.

Norway spruce (photo from Wikimedia Commons)

The trees are easy to identify because their drooping branchlets make the tops of the branches look bare. They also have the largest cone of any spruce …

Norway spruce branches and cones (photo by bitsorf via Flickr Creative Commons license)

… with papery thin scales and winged seeds.

Picea abies cone and seeds (photo from Wikimedia Commons)

If you find a mature Norway spruce deep in Pennsylvania’s woods, chances are you’ve found the site of an old homestead. It had to be planted in North America.

(photos form Flickr Creative Commons License and Wikimedia Commons; click the captions to see the originals)

The Trees With Leaves Are…

Yellow leaves and bare trees, Schenley Park, 23 Nov 2020 (photo by Kate St. John)

24 November 2020

By now all the leaves have fallen in the Pittsburgh area. Or have they? There are still a few trees with bright yellow leaves in Schenley Park — Norway maples.

As their name implies Norway maples (Acer platanoides) were imported from Europe where their native range extends further north than Pittsburgh.  Our short November days are the same length as those they experience in October back home.  The sun will be up for 9 hours and 39 minutes today, 24 November, in western Pennsylvania.  That’s the day length on 21 October in Oslo, Norway.

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

Because non-native plants are out of synch with our seasons late November is the best time of year to see them in the landscape.

The trees with leaves are aliens!

Fun fact: Pittsburgh’s latitude is very far south of Scandinavia. Did you know we are on the same latitude as Madrid, Spain?

Quiz: What North American city is nearly the same latitude as London, England? The answer is surprising.

(photo by Kate St. John)

Outdoors in Warm November

7 November 2020

Pittsburgh’s weather has been down-and-up from 30 degrees F + snow on Monday to 70 degrees F + sun today. By the end of the week it was fun to spend time outdoors.

On Friday I noted that most trees in the City of Pittsburgh still have leaves but few were as colorful as the sweet gum (Liquidambar styraciflua), above, in Scheney Park. American goldfinches moved among the leaves searching for seeds in the sweetgum balls.

The return of warm weather reactivated insects who were hiding from the cold. On Thursday a leaf-footed bug walked up our living room window.

Leaf-footed bug, 5 Nov 2020 (photo by Kate St. John)

White-tailed deer seem to be everywhere, especially in the city parks. The rut is in progress so the deer are less wary of people and cars. Meanwhile small trees in Schenley Park show new damage after bucks rub the velvet off their antlers.

Buck rub on an understory tree, 6 Nov 2020 (photo by Kate St. John)

Some trees have the perfect defense against such assaults. Large thorns adorn the trunks of honey locusts (Gleditsia triacanthos). No buck rubs here!

Honey locust thorns, Schenley Park, 6 Nov 2020 (photo by Kate St. John)

The warm weather will continue next week. It’s (still!) time to get outdoors.

(photos by Kate St. John)

Nature’s Bird Food and Other October Delights

Rose hips, Frick Park, 3 October 2020 (photo by Kate St. John)

This October there are plentiful fruits and seeds for migrating birds in Pittsburgh. Virginia creeper, porcelain berry, and rose hips (above) provide food for cedar waxwings and robins.

Pine siskins invaded southwestern Pennsylvania this week! Many of you are reporting them at your backyard feeders while natural food sources, such as arborvitae, have created pine siskin hotspots. Siskins force open the cones with their sharp beaks and pick out the seeds.

These arborvitae cones were on the ground at a pine siskin hotspot. Three stages are pictured: Top = Spent cones as much as one year old, Middle = Opened cones that were emptied by pine siskins, Bottom = a mix of closed, opened and spent cones.

Arborvitae cones that fell on N Dithridge Street thanks to pine siskins, 9 Oct 2020 (photo by Kate St. John)

The huge acorn crop in Schenley Park is attracting many blue jays, squirrels and chipmunks. Here’s what the ground looks like below the oaks at Bartlett Shelter.

Many, many acorns, Bartlett Shelter Schenley Park, 7 Oct 2020 (photo by Kate St. John)

In other delights October trees, sky and shadows are spectacular.

Fall colors, Schenley Park, 7 Oct 2020 (photo by Kate St. John)
Long shadows, Schenley Park, 7 Oct 2020 (photo by Kate St. John)
Fall color in Frick Park, 6 Oct 2020 (photo by Kate St. John)
Dead hickory points to the moon, 8 Oct 2020 (photo by Kate St. John)

It’s a good time to be outdoors.

(photos by Kate St. John)

A Big Year For Acorns

Acorns litter a sidewalk on Tennyson Ave, Pittsburgh, 27 Sept 2020 (photo by Kate St. John)

1 October 2020

When Rob Protz mentioned last week that a pin oak near his home is producing more acorns than he’d ever seen before I started paying attention in my neighborhood. Yes, there are lots of acorns in Oakland. It looks like a masting year for red oaks in southwestern Pennsylvania.

Acorns litter the grass in Oakland, Pittsburgh PA, 27 Sept 2020 (photo by Kate St. John)

Oaks are one of many trees that irregularly cycle their fruit production to insure that predators don’t eat everything. They boom or bust by synchronizing seed production. White oaks have a bumper crop in 3 years, red oaks on a 4 year basis. The bumper crops are called masting years.

Acorns in the red oak group take two years to mature so those falling now were formed in the spring and summer of 2019, influenced by spring precipitation, summer temperatures, the last killing frost, and each other.

North Oakland has a lot of oaks (duh! it’s the neighborhood name) so of course we have acorns on the streets. They make a hollow “ponk” sound when they fall on parked cars.

Check out the acorn crop in your own neighborhood. Is it a masting year where you live?

p.s. In masting years you’ll see more acorn predators — squirrels, blue jays and deer — as we did in the big acorn year of 2013.

(photos by Kate St. John)