Mark Stennes

This past week the world of trees lost a true friend. Mark Stennes was a tireless worker who selflessly promoted our urban trees and the people who worked with them and was a driving force behind elm research in Minnesota.

Mark Tree

When it came to trees, there are few people who could equal Mark’s passion. He had an insatiable curiosity in the world around us. He lived trees and took every opportunity to discuss them. He discovered the St. Croix elm and helped the University of Minnesota’s elm project identify other elms with potential. Any short list of tree experts in Minnesota had to have Mark’s name on it to be complete.

But as good as Mark was with trees, that wasn’t really where his genius lay. Mark was one of those rare individuals who was able to communicate that love for trees to other people and inspire them to actually do something. He was widely known and respected across the Green Industry in Minnesota. When Mark wanted to get something done, he did it through a tight network of friends that was incredible to behold. He had connections with people everywhere, from the tree people to the turf. Everyone knew that Mark was a person you could count on. A person who would go to bat for you when things got tough. For me, Mark was the guy who worked behind the scenes to make sure that everyone knew the kind of work that we were doing at the University of Minnesota, quietly promoting us so that when push came to shove we would have what we needed to make it all work. He took pride in the successes of his friends and wasn’t shy about spreading praise around. Mark was a person that I could constantly and consistently count on.

The day before he died, Mark called up my good friend Chad Giblin about going out and checking on some elms. And that’s how I’ll remember him; anxious to go and look at another tree so he could take notes and tell us all about it.

Plant sentience – “It is happening…again”

Those of you who were Twin Peaks fans will recognize the title quote. And while my topic is not quite as scary as being stalked by Bob, the fact that plant sentience continues to rear its irritating head in legitimate scientific venues makes me want to curl up in a ball and whimper. Here’s what made me cringe: “Sound Garden: Can Plants Actually Talk and Hear?”

I posted on this topic a few years ago, and I’d invite you to read it and the accompanying comments. I’m still not a fan of anthropomorphizing plants, and I still think word choices matter, especially when you are trying to educate people about science.

It’s disappointing that some scientists are deliberately using anthropomorphic language when discussing plant physiology. The cynical side of me says it’s a great way to get press coverage.

April 2013 041 We’re watching you…

When worlds collide

This past week I was in Alnarp, Sweden to present at the International Urban Tree Diversity Conference. Lots of interesting talks, posters and field tours. Much more to discuss than I can fit into a blog post, but if you’re interested you can read the presentation abstracts.

One of the best features of the conference is that the presenters and participants included not only arborists and urban forester but also landscape architects and urban planners. This might not sound too remarkable but these groups are not always on the same page. While urban foresters are on board with the need to diversify urban and community forests; species diversity can be at odds with uniformity, which is a key element in landscape design. For example, a common application of uniformity in design is the installation of alle’s – long, uniform monoculture plantings along a street or path.

Fredicksberg alle in Copenhagen - street view
Fredicksberg alle in Copenhagen – street view

Fredicksberg alle in Copenhagen - pedestrian view
Fredicksberg alle in Copenhagen – pedestrian view

The aesthetic appeal of an alle’ is undeniable and seemingly universal. We saw many examples in our tours in Malmo and Copenhagen, but alle’s can found almost anywhere mankind has planted trees.

An alle of beeches in Malmo. Sweden
An alle of beeches in Malmo. Sweden

The dilemma, of course, is that any monoculture planting runs the risk of catastrophic failure, especially in an era of increased global trade and potential introduction of destructive exotic pests.

Lindens failing in Fredricksberg alle
Lindens failing in Fredricksberg alle

Simply planting a random mix of species leads to a menagerie effect – one of these, one of those – that most eyes find unsatisfactory.

A random mix of species increases diversity though not necessarily aesthetic appeal
A random mix of species increases diversity though not necessarily aesthetic appeal

One of the challenges addressed at the conference is how to meet the design and aesthetic objectives of uniformity while still achieving diverse landscape. There are no simple solutions and like most compromises, not everyone will be completely satisfied. But at least we are getting to the point where all sides of the discussion are being heard and creative minds are melding the science and the art that will produce the desired aesthetic and diversity.

Another close shave…

Life is full of surprises. A case in point is some recent work on our Social Media Designed Tree Establishment Study (SoMe-Ded-TrEeS). One of the objectives of the project was to determine the impact of root-ball manipulations to remove circling roots on container-grown trees. When we planted the trees (‘Bloodgood plane trees in 25 gal. containers) two years ago, we ‘shaved’ the outer roots on one-third of the trees, ‘teased’ apart the circling roots on one-third, and planted the rest as-is (‘pop and drop’ in Linda’s vernacular).

Rerearch assistant Aniko Gaul shaves a root system  with a pruning saw before installation 2 years ago
Rerearch assistant Aniko Gaul shaves a root system with a pruning saw before installation 2 years ago
Research Technician Dana Ellison teases apart a root-ball before installation
Research Technician Dana Ellison teases apart a root-ball before installation

Two weeks ago our campus nursery staff dug 12 of the trees for us using their tree spade – four from each of the three groups. We then borrowed an air-spade from MSU Campus Infrastructure and Planning and we excavated the root-balls to determine the amount of new root growth into the surrounding soil. (‘We’ meaning my technician Dana Ellison and Nicole Rowley, one of our new undergraduate research assistants)

Dana takes a turn with the air spade
Dana takes a turn with the air spade
Nicole excavating roots with the air spade
Nicole excavating roots with the air spade

The results of the root exam were a surprise to me. Going in to this exercise my expectation was that the roots that were ‘teased’ to remove girdling roots would fare the best – and they did have visibly fewer circling roots and more new root growth than the ‘pop and drop’. But the biggest surprise was the marked improvement in rooting of the ‘shaved’ roots.

control root systems
control root systems
'Shaved' root systems
‘Shaved’ root systems

To be honest, I had some reservations about the shaving treatment. Just based on geometry alone, shaving off the bottom and outer 1” of roots around a 25 gal. tree removes over 20% of the roots; and this proportion is even greater is you consider the proportion of fine, absorbing roots. In the sampled trees, however, shaving essentially eliminated all circling roots. Even more impressive was the amount of new root growth out of the bottom of the root-balls. NOTE: In the photos below the red-dashed lines indicate the approximate dimensions of the roots when the trees were planted two years ago.

Root system on untreated control tree
Root system on untreated control tree
Root system on 'teased' tree
Root system on ‘teased’ tree
Rot system on 'shaved' tree
Rot system on ‘shaved’ tree

We (again meaning Dana and Nicole) trimmed all the roots that extended beyond the original root-ball and separated roots based on whether they came from the side or the bottom of the root-ball. They (the roots, not Dana and Nicole) are in the process of drying in the lab and will be weighed shortly. Based on the volume of material in the bags, however, it is clear the shaved trees will be the ‘winners’. Another example of why it pays to keep an open mind when doing research.

You and me Baby ain’t nuthin’ but mammals…

As spring slowly makes it appearance in the Midwest, homeowners and landscapers are likely to continue discovering damage from our record-breaking winter. While brutally cold temperatures and heavy snow loads took their toll in many areas, some of the most severe damage that occurred to landscape trees and shrubs this winter was caused by mammals.

Our long, harsh winter resulted in heavy feeding damage by deer, rabbits and voles, also called field mice. Depending on the age and type of plant and which animal was feeding on it, mammal damage can range from light pruning to death of a tree or shrub. Developing a strategy to deal with animal damage requires proper identification of the offender. Here are clues to identifying mammal damage.

Vole damage
Voles or field mice are small rodents that gnaw on tree and shrub stems. Voles do not hibernate and are active throughout the winter under snow, so feeding damage that occurred near ground-line when the ground was covered with snow is likely vole damage. Although they are small, voles can wreak a lot of havoc. They can easily kill small trees or branches on larger trees by girdling stems, or removing the bark around the entire circumference.

Vole damage on concolor fir
Vole damage on concolor fir

Voles (or field mice) can completely girdle trees.
Voles (or field mice) can completely girdle trees.

Deer damage
During the winter, deer feed on the ends of many types of trees and shrubs. Evergreens, especially arborvitae, are among their favorites. In most landscapes in this area, a “browse line” is a common feature on arborvitae. Eastern white pine, maples, birch, dogwoods and viburnums are also favored trees deer browse. This winter, I received reports of deer browsing on secondary species, such as Austrian pine, reflecting the severity of the winter.

A deer browse line on arborvitae.
A deer browse line on arborvitae.

Rabbit damage
Rabbits can cause damage that may resemble feeding by either voles or deer. Like deer, rabbits will chew the ends off of deciduous trees and shrubs. A close inspection of the end point will often indicate the culprit: rabbits typically leave a clean, angled bite mark, whereas deer tear or break stems, leaving a rough edge. Like voles, rabbits can also girdle stems of trees and shrubs. In winters with heavy snow cover like this one, the height of the damage can provide a clue; vole damage will extend down to the soil surface, while rabbits work above the snow-line.

Clean, angled bite-marks: A telltale sigh of rabbit activity.
Clean, angled bite-marks: A telltale sigh of rabbit activity.

Managing mammal damage
Managing mammal damage is often difficult and multiple strategies may be needed. Excluding deer with fencing can be highly effective, but is not practical in many instances. Deer repellents can also be effective, but may wear off over time or become less effective as deer become hungrier as winter wears on. Around our place, our dogs to a good job of keeping deer and rabbits at bay, but of course require their own care and feeding.
Reducing weeds and ground cover can help to reduce damage by rodents by eliminating cover from their predators. Trapping may be effective for controlling rabbits, but is usually not practical for voles. Baiting can be used for voles, though care must be taken to avoid poisoning non-target animals. In some situations, erecting raptor perches can also be helpful in keeping rodent populations down.

Go ahead, weed, make my day…

Ridding an ecosystem of invasive plants is never easy. We can bring in goats to munch on offending plants or force armies of schoolchildren into slavery to pull them out; but, in all likelihood the sneaky little devils (the invasive plants, not the schoolkids) will be re-sprouting and back with a vengeance before we can turn around. For many invasive plant infestations the most practical long-term solution is chemical control – in other words, herbicides. Of course, herbicides have their issues such as drift and potential impacts on non-target plants. And what do you do when you want to get rid of invasive plants in a remote, sensitive ecosystem with limited access? Enter Herbicide Ballistic Technology (HBT). The HBT system uses the same technology as a recreational paint-ball gun but instead of filling the projectiles with paint, the balls are filled with triclopyr, which is commonly used in homeowner products for brush and poison ivy control.

Dr. James Leary at the University of Hawaii has been exploring the use of HBT to control invasive plants in various ecosystems in Hawaii. Most of the time Dr. Leary and his colleague use the standard paintball HBT system, but for the big jobs they call in the heavy artillery – literally. Dr. Leary recently presented a seminar here at MSU on work he and his team have conducted in conjunction with the Maui Invasive Species commission to eliminate populations of Miconia calvacens, one of the most problematic invasive trees in Hawaii. According to the seminar abstract, Dr. Leary reports “Our best utility for HBT deployment on a Hughes 500D helicopter platform featuring real-time capabilities in target elimination. …we have conducted 17 tactical search and destroy mission covering a total net area of 3,888 ha and eliminating 7,463 Miconia targets.”

Targeting miconia from a helicopter. Photo: C. Duncan.
Targeting miconia from a helicopter. Photo: C. Duncan.

Clearly the war on invasive has been raised to a different level

Feel the burn…

Winter burn on Douglas-fir
Winter burn on Douglas-fir

One of the most obvious impacts of this winter’s winter is rapidly becoming apparent in Michigan and other parts of the Midwest: winter burn on conifers. The primary symptom of winter burn is needle browning, especially on evergreen conifers in exposed locations. Needles may be damaged by extreme cold or the browning may be associated with winter desiccation as needles lose moisture during brief warm-ups. Winter burn is one of those situations that draws a lot of attention because it can look devastating; yet it often has relatively little long-term impact on plants.
Winter burn on dwarf Alberta spruce in Michigan
Winter burn on dwarf Alberta spruce in Michigan

The key to the lasting effects of winter damage on evergreens is the extent to which buds are damaged.
With a little practice it is relatively easy to determine the state of conifers buds. With your thumb and forefinger pull the bud scales from the top of the bud. With a good hand lens or dissecting scope you will be able to see the bud primordia. On healthy buds this will be bright green; on damaged buds the primordia with be brown or black.
Buds from conifers with severe needle browning may be alive (top) or dead (bottom).
Buds from conifers with severe needle browning may be alive (top) or dead (bottom).

I recently examined buds from Douglas-fir trees on campus that had severe needle browning this winter. In several cases, trees had severe needle browning but the buds were fine. These trees will likely put on a normal growth flush this spring and in a year or two it may be difficult to tell they were ever damaged – assuming we don’t have a repeat of this winter’s severe weather.
A 'snow-line' indicates the depth of snow when needle injury occured
A ‘snow-line’ indicates the depth of snow when needle injury occured

On some other trees, however, the buds had been killed by this winter extreme cold. This doesn’t mean these trees are dead – they may still form adventitious buds along the stems – but it will certainly set them back and will likely impact their form and symmetry.

Bert, I’ll see your SOME-DED-TREES with POOR-DEAD-TREES

Bert’s done some nice posts on his SOcialME DesignED TREE transplant Study (or SOME DED TREES). I’m going to add to the discussion with a new addition to my Preventing Optimization Of Roots DecrEAseD TREE Survival (or POOR DEAD TREES) series.

It took a while, but the prediction I made in 2010 has come true. You’ll have to look at the link to see the whole story, but the bottom line is that this tree lasted only 7 years before succumbing to poor planting practices.

Here is the tree when it was planted in 2007. Note the lack of root flare (planted too deep) but the very obvious presence of orange nylon twine around the roots and the trunk.

Pine%202007.jpg   Orange%20twine.jpg

Here it is again in 2010. Note the dieback at the top and overall chlorosis.


And here it was yesterday.

Bush tree 2014Yes, it’s dead – dead and gone. I’m not sure exactly when it was removed, but it lasted less than 7 years. Conifers have lifespans of decades or centuries. There was no excuse for this poor installation, though I keep getting the argument from landscape installers that it costs too much to do it right (i.e., to remove the twine and burlap, if not the clay itself). Keep in mind that warranties only last for a year, so the property owner gets to eat the replacement cost caused by crappy installation practices.

We GP’s may continue to disagree about how much rootballs should be disturbed when planting, but I know that none of us would agree that planting B&B trees intact is a good idea.

Spring = really?

You've got to be kidding...
Bebe the Wonder Dog says “You’ve got to be kidding…”

I’m sorry I’ve been so quiet, but I am not feeling SPRING. Here in the Blue Ridge of Virginia (Zone 6), March is averaging 10 F below average. Snow and ice is piled up on the north side of buildings. My Herbaceous Landscape Plants class is not impressed by the inch-tall Mertensia and the fact that the only thing we can call a cool-season annual (pansies/violas) is brown mush. All the delightful Zone 7 things I’ve been pushing on people for several years here – er, whoops. This is as far north as I’ve ever lived (please don’t mock me Bert). I’m tired of bales of laundry. Flannel sheets, corduroy, fleece…I am NOT good with winter. I admit I am at my best with only one layer on. And if one more person says “at least we’ll have fewer ticks”…

California here we come…

Linda and I are in Sacramento this week for the National eXtension Conference. I will be presenting later in the week on the work that we have done on the SOME-DED-TREES project. More on that in later posts. In the meantime, here are some photos from the State Capitol Park here in Sacramento. If you are ever in the area, I encourage you to check it out since the Park also doubles as an arboretum. The combination of mild winter temperatures and irrigation allows for as wide an array of trees as you are likely to see on one location. Many, but not all, of the trees have tags with common and scientific names. There are also numbered tags for a “Tree tour”. I have searched several sources for the tour map and came up empty. Judging by the condition of the tags and the number of missing tags, it looks like a forgotten project. If anyone has any insights, let me know. Or if you know an Eagle Scout in the Sacramento area, re-tagging and mapping would make a great project.

Palm tree tagged on the State Capitol Park Tree Tour

Italian stone pine Pinus pinea

Bark pattern (looked to be some type of Cuppressus but tag was missing

Tags need some work…

Lots of nice coast redwoods (Sequoia sempervirens)

Giant sequoia (Sequioadendron giganteum) as a street tree? These actually looked like they were doing well and then hit the wall. Note the fading top.

The park also includes a small rose garden and cactus garden.

You can hedge almost anything if you’re determined, even azaleas…

DSC_1396Just for Linda: Topiary at the hotel across the street.

Cork oak (Quercus suber)