Category Archives: Trees

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)

Bug Finds Food Using Infrared

Western conifer-seed bug (photo by Dawn Dailey O’Brien, Cornell University, Bugwood.org)

Back in 2008 a team of scientists made an amazing discovery: the western conifer-seed bug uses infrared sensors to find his favorite food.

Western conifer-seed bug (photo by David Cappaert, Bugwood.org)

The western conifer-seed bug (Leptoglossus occidentalis) is a North American sucking beetle that resembles a stink bug, though he’s not in the stink bug family. Ornately marked and 1/2 to 3/4 inch long (16-20 mm), he feeds on the sap of developing pine cones. This causes the seeds in the cones to wither which is only a minor problem in western forests but a big deal at pine seed orchards.

The seed bug used to be confined to temperate forests of the Pacific coast but has naturally expanded his range all the way east to Nova Scotia. In the past 20 years he’s been accidentally imported into Europe, Chile, and Japan so there’s international interest in how this bug finds pine cones at a distance.

The 2008 study led by Stephen Takács, Infrared radiation from hot cones on cool conifers attracts seed-feeding insects, found that pine cones emit infrared light at all levels and the western conifer-seed bug can “see” it.

Pine cones emit infrared light because they’re warmer than the rest of the tree by almost 60 degrees F. These photos from the study, taken in normal and infrared light, explain: “The temperature bar to the right of the paired images reveals that cones are up to 15°C warmer than foliage under high-cloud conditions.”

Conspicuousness of western white pine cones in mid-range and long-range IR spectrum thermographs. (a) visual spectrum photographs (b) thermographs (image from Royal Society Publishing 2008.0742)

To prove that the bug is attracted to infrared, researchers set up infrared emitters shaped like pine cones (photos below). Did the bug approach them? Yes, it did. Could the bug find the cones when his IR sensors were experimentally blocked? No he could not.

As the study explains:

Here, we show that the western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae), a tissue specialist herbivore that forages during the photophase and feeds on the contents of seeds within the cones of many conifers (Blatt & Borden 1999; Strong et al. 2001), uses IR radiation from developing cones as a long-range foraging cue. We present data revealing that (i) cones are warmer and continuously emit more near-, mid- and long-range IR radiation than needles, (ii) seed bugs possess IR receptive organs and orient towards experimental IR cues, and (iii) occlusion of the insects’ IR receptors impairs IR perception.

Infrared radiation from hot cones on cool conifers attracts seed-feeding insects, Stephen Takács et al, Royal Society Publishing

Apparently the world looks very different to a western conifer-seed bug. For him the pine cones really stand out while the rest of the world is boring.

postscript: NOTE that the western conifer-seed bug (Leptoglossus occidentalis) is not the scourge of our western pine forests. The forests are being killed by a completely different native bug — the mountain pine beetle (Dendroctonus ponderosae) — whose larvae make galleries under the bark and kill the tree from inside. Below: Pines killed by the mountain pine beetle, Galleries under the bark, and the mountain pine beetle.

Mountain pine beetle (Dendroctonus ponderosae) and its damage (photos from bugwood; see citations and links below)

photo credits: Click on the captions to see the originals.
* Infrared images from study at Royal Society 2008.0742, Creative Commons license
* Western conifer-seed bug photos from Wikimedia Commons
* Mountain pine beetle row of photos:
#5540352: Kill at Deadman Road, CO, William M. Ciesla, Forest Health Management International, Bugwood.org, #UGA1254003, Galleries, William M. Ciesla, Forest Health Management International, Bugwood.org, #UGA1306005, mountain pine beetle, Dendroctonus ponderosae, Ron Long, Simon Fraser University, Bugwood.org

This topic was inspired by a 2008 article from Nature’s Crusaders blog: Pine Beetle Uses Infrared to Find Next Meal

Get Thee To A Shrubbery

The “ultimate green square,” Leylandii enclosing a tennis court (photo from Wikimedia Commons)

Even when a species is invasive, nurseries sell it and people plant it until it’s banned. Consider the case of Leylandii trees, sold as shrubs in the U.K.

At the garden center, the homeowners say, “I want something that grows quickly and provides some privacy.” They bring home these cute little shrubs.

Just planted, a cute little Leylandii shrub (photo from Wikimedia Commons)

But Leylandii grow three feet a year. Eventually the shrubs are so tall they have to be trimmed using ladders, like the “ultimate green square” in the photo at top.

The hedges eat the bus stop …

Leylandii eat the bus shelter (photo from Wikimedia Commons)

… and engulf the lane.

Leylandii crowd a lane (photo from Wikimedia Commons)

On Throw Back Thursday read how these “privacy” shrubs can spark fights among the neighbors in this vintage post: Plant A Shrub, Start A Fight.

(photos from Wikimedia Commons; click on the captions to see the originals)

p.s. Shakespeare fans will recognize my allusion to Hamlet’s madness.