Going off half-cocked

The good news about being a landscape extension specialist is you get to comment on a variety of landscape tree problems.  The bad news?  You get to comment on a variety of landscape tree problems.  In an average week I probably get 10-15 tree-related calls or e-mails from homeowners, landscapers, growers, extension educators, lawyers, newspapers, and on and on.  Sometimes the problem is routine and obvious like tar spot on maples; “I have these spots that look like tar on my maple leaves…”  Sometimes the problem looks routine and turns into something else entirely different like the Imprelis herbicide debacle.  With the number if problems I respond to, invariable I sometimes end up shooting from the hip – and miss the mark.

Red maple with sparse canopy (right foreground).  Maple in left-center of picture across the road was planted at the same time.

A few weeks back I noticed some red maples on campus that were struggling as they were starting to leaf out.  There were planted about three years ago following a road-widening project.  They are located on a tough site between a parking lot and a busy 4-lane road.  My immediate diagnosis was they were weakened due to the aftereffects of last year’s sever heat and drought.  I even included a photo of them in an article I did for our on-line extension news.  Then this morning I happened to talk to a friend from our campus landscape services.  “Boy, those maples sure took a beating from the drought last year”, I volunteered.  My Landscape services friend replied, “Well, that and we hit them with Shortstop last year…” Uh oh, now the conversation was going in a different direction.  Shortstop is a plant growth retardant, the active ingredient is paclobutrazol, which inhibits GA synthesis in plants and is being widely used by arborists to reduce the need for tree pruning.  In this case it worked a little too well and the trees ended up being stunted.

Leaves of paclobutrazol-treat maple (left); untreated leaves on right.

In my defense, I was partly right.  Under normal weather patterns paclobutrazol applied at the labeled rates (as was done here) would have reduced shoot growth and leaf growth but clearly the drought exaggerated the effect.  So, another lesson learned (actually re-learned) never assume anything about trees until you talk to the people who actually take care of them.

Sheep-eating flowers?!

I was planning to follow up on Jeff’s phosphorus post with a bit more “phun with phosphorous.” However, I was completely derailed by Ray Eckhart’s message and link left for me on our GP facebook page with this headline:

RHS ‘sheep-eating’ plant about to bloom in Surrey

“The Royal Horticultural Society (RHS) at Wisley said the Puya
, a native of Chile, would bloom in the next few days and last
about a week.

In the Andes it uses its sharp spines to snare and trap sheep and other animals, which slowly starve to death.”

“The animals then decay at the base of the plant, acting as a fertiliser.”

[Dear BBC News: “Snare” and “Eat” are not really interchangeable]

How…have I not heard of this before.

I’ve posted previously on my Puya fixation. I asked readers to bet on how long it would take for me to kill my wee Puya bertoniana, mail-ordered from Annie’s Annuals.  I am happy to report that it made through the winter (greenhouse) and is now sunning itself on our deck.

Now this really ups the ante – it captures sheep!  Maybe P. bertoniana isn’t as robust as P. chilensis though. Perhaps…a vole or rabbit?

Phosphorus and Big Macs

Minnesota, and I were cruising through old pictures and files and getting all sentimental about the cool stuff we used to do.   A lot of it was never published just because after we were done with one thing we were just too damn excited to move on to the next.  Anyway, one of the neatest experiments that we never wrote up was a phosphorus experiment.  Here’s what it looked like to the casual observer.

Now let me explain the neat part to you a little.  Inside those boxes, underneath three of the six plants in each container, are vials set up like this – three vials per plant (the black tubes provide air to the vials).

Each plant had one root placed into each of the three vials – one vial contained 1 ppm phosphorus, one vial contained 10 ppm phosphorus, and one vial contained 30 ppm phosphorus.  The tub itself was also filled with one of these three solutions (1, 10, or 30 ppm phosphorus) as seen below.

At the end of the experiment we weighed the roots filling each vial, as well as weighing all of the roots from each plant.  Here’s what we found for the individual vials.

As you can see, more phosphorus in a vial meant that the plant would devote more energy to growing roots there – but also notice that the 10 ppm solution has the greatest mass of roots overall.  Here’s what we saw when we looked at the total size of all of the roots from plants for the different solutions.

As you can see, the roots from the plants in the 10 ppm solution are the largest (shoots showed the same trend).  So here’s the way I see it (this is the Big Mac part).  I love Big Macs.  If I see a McDonald’s I want to go in there – I gravitate towards McDonald’s to get Big Macs.  But too many Big Macs aren’t good for me.  They might even stunt my growth!  It’s the same for phosphorus.  Roots do grow towards phosphorus (this isn’t technically correct, but it works for my analogy so I’m sticking with it!), but that doesn’t mean that a tremendous amount of phosphorus is actually good for them.  In fact, it might even stunt their growth!  This could be for a variety of reasons, but most likely because the phosphorus would interfere with the uptake of other elements.

Label GMO foods? Sure, why not?

Lots of coverage in the mainstream media these days over various initiatives to label GMO foods.   I think GMO foods should be labeled; but not for the reasons you might think.

My personal opinion on GMO foods is that their benefits outweigh the potential downsides.  I think GMO foods should be labeled to make the public aware of how much of our food supply depends on GMO’s and the cost of not using GMO’s.  Obviously this will raise some social justice issues since wealthy people will have more opportunity to opt out of buying non-GMO products than the poor but it’s the same problem we have with organic already and it doesn’t seem to cause much of a stir.  My hope is that once GMO products are labeled we could get to the point where the main discussion on GMO’s focuses on the rational and scientific questions, not the irrational and emotional.  This weekend our Sunday paper included a quote from a local anti-GMO activist who tried to link the rise in obesity to increased use of GMO’s.  How about we’ve become too sedentary and we’re eating too much, period?  Or this from the “Health Ranger” Mike Adams: “Roundup herbicide devastates soils, rendering them contaminated and unable to produce healthy crops using traditional (or organic) farming methods. Once a farm plot is destroyed with Roundup, that farmer is forever enslaved to a chemical-based farming protocol.”   Hmmm… last time I checked farms could be certified organic after three years without synthetic chemicals.

Which is not to say I don’t have concerns about GMO’s; there are issues with any technology.  The largest questions I see, and the ones that are most difficult to answer, relate to unintended consequences.  One of the biggest selling points of Round-up ready technology, for example, is that it enables farmers to manage weeds with glyphosate, a relatively safe product in the world of industrial-strength herbicides, in order to reduce tillage and maintain crop productivity.  But as farmers use more and more glyphosate, they are also selecting for Round-up resistant weeds.  How long until glyphosate is no longer effective? Difficult to predict, but glyphosate resistance has already evolved in many weeds.

On the other side of the equation, the world’s population is projected to exceed 9 billion by 2050, with a disproportionate increase in the least developed countries.  As the need for food increases, land and water resources will become more limited and catastrophic droughts are likely to increase.  While it is easy to demonize industrial agriculture, it’s difficult to envision feeding ourselves and the world without the technology it has developed.


Mosses are soft, green, and tough as nails, as shown in a recent article in the Proceedings of the National Academy of Science (prestigious, high impact journal with a rather unfortunate acronym).

Dr. Catherine La Farge and associates, from the University of Alberta, visited a remote glacier on Ellesmere Island, Nunavut while studying the wild, wide world of arctic bryophyte systematics. Bryophytes are ancient, non-vascular, non-flowering plants – mosses and liverworts, mostly.

Long story short, they harvested bits of moss that had been trapped in ice for about 400 years and were now exposed. Several species were collected, taken back to the lab, ground up, placed on growing media in a growth chamber, and they soon had mosses galore. 

This is fascinating on several levels, as pointed out by the authors.  One is the power of totipotency – the ability of a cell to “de-differentiate into a meristematic state that can then reprogram the cell for development of the organism”  a la stem cells.  Another is the mosses’ ability to “shut down” when dry and “revive when conditions are favorable” (like not frozen in ice for 400 years?!)

The article also graphs the disturbingly accelerating rate of retreat of the Teardrop Glacier, where the mosses were collected. Aargh. The window of favorable conditions may not be open long for these little wonders.


Today I want to share something that I’ve been working on recently with Fine Gardening that is really cool!  So you know all of those lights you can buy to get your plants started over the winter?  Did you ever wonder which of those lights really work?  I’m going to leave the final answer for my article, but let me tell you, there’s a world of differences between the lights.  The best seem to be some LED lights that aren’t available yet, but are made by a company called Heliospectra.   Mostly they make high end lights for commercial producers and researchers, but they will be entering the home market soon.  Man, these lights are SWEET!

Interestingly, the other LED lights fail miserably because their light is so columnated (in other words the light doesn’t spread out), as you can kind of see in this picture (there’s another pic on facebook that shows it a bit better):

Most of you are probably using fluorescent lights, and, in terms of bang for your buck, I’d say those are pretty good.  We tested a bunch of different fluorescent, as well as incandescent lights.  Be on the lookout for the article in about a year!

The Canary in the Coal Mine

Three weekends ago marked a milestone of sorts as mean daily CO2 levels at the National Oceanic and Atmospheric Administration observatory at Mauna Loa, Hawaii topped 400 ppm for the first time ever.  Rising levels of CO2 and other greenhouse gases could result in significant increases in temperature in the Upper Midwest over the next century.  When we think about trees in cities the scenario is even worse since not only will urban trees have to deal with overall temperature increases but they must also contend with urban heat island effects, which can add another 8 deg. C or more of heat load.  Because of this ‘one-two punch’ of global climate change and urban heat island effect, I often refer to urban trees as the proverbial ‘canary in the coal mine’ with respect to climate change since they will likely be impacted sooner and more dramatically than trees in woodlands.



In general, organisms have three options to deal with a change in their environment: They can migrate, they can adapt, or they can acclimate.  Since trees are sessile organisms, they can’t pick up and move so migration is out.  Current predictions are that climate will change faster than trees can evolve so natural selection and adaptation will be limited.  Which leaves us with acclimation, or the ability of a tree to adjust its physiology and morphology to its environment.  A common example of an acclimation response is the development of sun and shade leaves on the same tree.  Another example of an acclimation response is an increase in the optimum temperature for photosynthesis in response to exposure to increasing temperatures.  In theory, trees that have a greater capacity to adjust their physiology to increasing temperature will be better suited for future, presumably warmer climates.

We are currently testing this idea in a two-part study.  In part one we are growing trees from several shade tree cultivars in greenhouses under three temperature regimes; ambient temperature, ambient + 5 deg. C, and ambient +10 deg. C.  In part two of the project we planted trees of the same cultivars in two sites in Detroit in cooperation with the Greening of Detroit.  The Greening of Detroit is community based non-profit organization that assists neighborhood groups, churches and schools in their efforts to improve the ecosystem in Detroit through tree planting projects, environmental education, urban agriculture, open space reclamation, vacant land management, and workforce development programs.

Many hands make light work.  Greening of Detroit volunteers plant trees along a street median.

With the help of Greening staff and about 90 Greening volunteers, we recently planted 160 shade trees in downtown Detroit.   One site of the study is in a park, representing a relatively mild micro-climate; while the other site is along a street median surrounding by asphalt with a much higher reflected heat load.  Both sites with be instrumented with environmental sensors and we will compare growth over time as well as physiological responses such as the response of photosynthesis to temperature.  The long-term goal is to identify traits that will be most important to guide future selections of trees of urban and community forestry under changing climatic conditions.

Research Technician Dana Ellison (left) and Research Aide Aiman Shahpurwala finish planting a park tree.

A pick ax as a planting tool?  Dana shows how it’s done in Detroit.

Should back-fill be amended?  My usual answer is ‘no’, but then again it depends what your back-fill looks like…

Sizing things up.  Aiman and Dana collect initial data on trees after planting.