Category Archives: Trees

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)

Tiny Jumping Beans

Jumping oak galls, Neuroterus saltatorius (photo by Donald Owen, California Department of Forestry and Fire Protection via bugwood.org)

24 July 2020

There’s a cool thing happening in California right now that we never see in Pennsylvania. In neighborhoods with white oaks there are tiny “jumping beans” in the gutters.

Here’s that they look like, recorded a week ago by Mary K Hanson.

They’re even better in slow motion, recorded by Mark Eagleton in Woodland, California.

Though they resemble the moths called “Mexican jumping beans” (Cydia deshalsiana) these galls are the agamic (asexual) second generation of tiny Neuroterus saltatorius wasps that mature on white oak leaves and fall to the ground.

Neuroterus saltatorius 2nd generation galls on back of oak leaf (photo by Steve Katovich via bugwood.org)

The larvae are tightly packed inside the galls so when they move the galls jump up to 3 cm. That’s 30 times the size of the gall!

In the fall the larvae become adult wasps inside the galls and overwinter to emerge next spring.

Neuroterus saltatorius are native to western North America from Texas to Washington state and up to Vancouver Island, Canada. That’s why we don’t see them in Pennsylvania.

Learn more at the University of Florida’s Department of Entomology: Neuroterus saltatorius.

(photos from Wikimedia Commons and bugwood.org; click on the captions to see the originals. videos embedded from YouTube)

Oh, Christmas Tree

If you have a live Christmas tree, it’s probably one of sixteen species of fir, spruce, pine, cypress or cedar. Many people prefer firs for their soft needles, but firs dry out quickly and drop their needles fast. One year our tree dropped its needles before Christmas!

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!

The 10 Best Christmas Trees You Can Buy — The Spruce

If the tree was sheared closely there’s no room to insert your hand or an ornament. Ouch, Christmas tree!

However Scotch pines have this advantage, and so do other live trees: If you feed birds in your backyard, place your old Christmas tree near the feeders to provide winter cover for birds.

(photos from Bugwood.org and Wikimedia Commons; click on the captions to see the originals)

Trees Remember Their Lives As Seedlings

New red oak leaves, April 2015 (photo by Kate St. John)

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.

Putting down roots: an acorn puts out a shoot, April 2017, Ohiopyle (photo by Kate St. John)

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.”

Red oak seedling, April 2019 (photo by Kate St. John)

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).

USDA Plant Hardiness Zone map for Pennsylvania as of May 2018 (map from USDA.gov)
USDA Plant Hardiness Zone map for Pennsylvania as of May 2018 (map from USDA.gov)

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.

Resources: Lab Girl by Hope Jahren and Forest trees remember their roots from Science Daily

(photos by Kate St. John, map from USDA)

Don’t Stake That Tree

Tree staking damage (photo from Wikimedia Commons)

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.

Tree stake was never removed so the tree grew over it, Schenley Park (photo by Kate St. John)

Still have questions? Get expert advice at Davey Tree blog, Gardening Know-how, or Northern Woodlands.

(photo credits: Wikimedia Commons (click caption for the original), and Kate St. John)