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?
One species, the Scots or Scotch pine (Pinus sylvestris), doesn’t lose its needles even when it’s completely dry. I’ve seen Scotch pines put out for trash collection in January that looked as if they were freshly cut. There’s a down side though, as described at The Spruce:
You’ll want to wear gloves when decorating a Scotch pine since its needles can be sharp as pins!
Just as our own experiences shape our response to the future, trees remember their lives as seedlings and it shapes their responses to environmental stress.
Arborists had long suspected a “nursery effect” in which transplanted trees of the same species seemed to respond differently to the same environment depending on the nursery where they were grown. A 2011 study by the University of Toronto at Scarborough used poplar tree nursery stock to examine this theory.
Poplar trees (Populus sp) are propaganted clonally so a cutting grown from a parent tree is genetically identical to the parent. The study obtained stem cuttings from the same parent poplar tree regrown in widely separated nurseries in Alberta and Saskatchewan. They then regrew the trees in Toronto under identical conditions with half exposed to drought, the other half well watered.
Amazingly the clones from Alberta responded differently than those from Saskatchewan. They even used different genes in their response.
“The findings were really quite stunning,” said Malcolm Campbell, lead author of the study. “Our results show that there is a form of molecular ‘memory’ in trees where a tree’s previous personal experience influences how it responds to the environment.”
That’s why it’s unwise to transplant a tree grown in Somerset County, PA to a backyard in Pittsburgh. The origin and destination climates are too different. The tree’s triggers are incorrectly set for its new life. (Somerset is zone 5b, Pittsburgh is 6b, on the Plant Hardiness Map).
This applies to forest trees too, even though they aren’t transplanted. Their previous experience could help their survival in the face of climate change, diseases and pests.
As winter arrives this week, watch the trees respond with their own history as a guide.
It’s tree-planting season and a good time to remember that trees can be damaged by our good intentions. In the old days we staked every newly planted tree but we’ve since learned that for most tree plantings, stakes are a bad idea.
Tree trunks become strong from the ground up by swaying in the wind. When a tree is staked, it “thinks” it already has strong roots where it’s staked so it puts effort into growing tall instead of establishing roots. The trunk becomes strong above the yoke and remains weak below it. In addition the yoke may damage the trunk, further weakening the tree as shown above.
If your new tree has a big root ball it probably doesn’t need to be staked, though there are exceptions quoted here from the Davey Tree blog. You should use stakes on …
Bare-root trees or trees with a small root ball.
Trees planted in areas with lots of foot traffic, like a sidewalk or street.
New trees that can’t stand on their own or those that begin to lean.
Eucalyptus trees, mesquite hybrid trees, oleander trees and acacia trees.
Tall, top-heavy trees with no lower branches.
Young trees if you live in a very windy area or if the soil is too wet or loose.”
If you use stakes make sure to remove them at the next growing season. If you don’t, the tree will grow around them like this one did at Schenley Park. See more photos at How Stakes Hurt Trees.