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.
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.
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.
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.
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.
Eastern redbud flowers (Cercis canadensis) had not opened in Schenley as of 7 April, but they showed promise.
Spring cress (Cardamine bulbosa) was blooming at Raccoon Wildflower Reserve on Easter Day.
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?)
Spring green will continue in the coming weeks as tiny leaves pop open and more trees bloom.
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.
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).
Other trees have swelling buds.
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?
Meanwhile daffodil leaves are turning green in Schenley Park.
Tulip leaves emerged on a busy street in Oakland where the deer can’t get them. 🙂
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!
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).
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.
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.
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.
Many stand alone.
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 …
… with papery thin scales and winged seeds.
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)
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.
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.
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.
Some trees have the perfect defense against such assaults. Large thorns adorn the trunks of honey locusts (Gleditsia triacanthos). No buck rubs here!
The warm weather will continue next week. It’s (still!) time to get outdoors.
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.
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.
In other delights October trees, sky and shadows are spectacular.
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 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?