Protecting existing trees – what a concept!

I just got back from a trip to Pullman where I guest lecture once a year for the Landscape Plant Management class.  It’s also a chance to get some new photos for my Wall-O-Shame.  Here’s my latest:

Pin oak (Quercus palustris) doesn’t drop its leaves in the winter – instead, they hang on until the following spring.  So it’s really easy to see which part of this tree is alive (i.e., has last year’s leaves).  It’s apparent that most of the crown has died, with only some lower scaffold branches remaining.

How did this happen?  Take a look at how new that concrete is around the base of the tree (and how small the tree well is.  This construction was done in 2004:

Note the complete lack of root zone protection.  Not only has the majority of the tree’s fine roots been destroyed in preparation for pouring concrete, but only a very small space under the tree is “protected.”  I guess the cup at the base represents the irrigation system.  To top it off, this construction was done in August, when coincidentally I was there as well.  It was blistering (as it usually is in the summer in eastern Washington), and the remaining leaves on this tree were wilted:

So why would anyone be surprised when, 6 years later, this tree looks like crap?  And why doesn’t WSU insist on tree protection standards when construction bids are submitted?

Friday mystery revealed!

Good sleuthing over the weekend!  As John, Karen, Jimbo and Al suggested, there is something stuck on the side of this Norway maple (Acer platanoides, which is Latin for “maple that takes over the planet”).  In fact, the reason that I, with my pathetic ID skills, know that it’s a Norway maple is because it’s a nursery tag stuck in the tree:

This type of injury really bugs me, because it’s entirely preventable.  One of the cardinal rules of transplanting trees and shrubs is to remove all foreign material.  And this is a perfect example of why.  I don’t know the history of this tree, but this is was I think happened.

The tag was on a branch of the young tree; as the branch increased in girth, it became girdled by the plastic and died back.  At the same time, the girth of the tree increased to encompass the base of the branch and the tag.  The dying branch was either torn from or broke off the trunk, creating a tear in the bark and creating the horizontal scarring at the base of the wound.

If you’re hopeless with plant names (like I am), keep an electronic database of all the plants you’ve installed in your landscape, including the name, the date installed, and any notes, especially for failures (e.g. not cold hardy enough, invasive, too large, slug snack, etc.).

An evolving view of plant nutrition

One of the hallmarks of science is that our view of the world evolves and changes as new evidence comes to light.  When I was a grade-schooler following the Apollo missions, for example, I knew all the planets in order from Mercury to Pluto and how many moons each one had; Jupiter was the champ with 12.  Today, Jupiter has as many as 63 moons depending on who’s counting.  And Pluto, let’s not even go there.   Likewise, our view of plant science has changed over the years.  As I’ve mentioned before, when I took introductory Botany as an undergrad thirty-some years ago we learned that there were 16 essential plant nutrient elements.  Since then we’ve learned that nickel is also essential at least for some plants.

 

If you took your plant science more than 10 years ago, you also learned that nitrogen is taken up from the soil as either ammonium or nitrate.  This view is now being revised due largely to evidence from the ecological literature.  Ecologists have found that in northern boreal regions where soil temperatures are cold and mineralization and nitrification rates are low, plants will take up intact amino acids from the soil (Nashholm and Persson, 2001; Kielland et al., 2006).  Recent studies have extended these observations to temperate forests (Gallet-Budynek et al., 2009) and horticultural crops. (Ge et al., 2009), indicating that a range of plants may be able to derive a portion of their N requirements directly from organic sources.

 

So what does this have to do with the Garden Professors and the science of landscape horticulture?  First off, this is pretty cool stuff and certainly will cause a lot of re-evaluation of some established paradigms.  From an applied perspective, fertilizing with amino acids and related organic source has some potential benefits.  In warm, well-aerated soils, nitrate-N predominates.  When plants take up nitrate, it must be reduced via nitrate reductase and nitrite reductase before it can be assimilated into amino acids.  These steps require metabolic energy.  In theory, amino acids could bypass the reduction and assimilation processes and provide a more efficient means of fertilization.  At this point, most of the scientific focus is on quantifying how much organic N can be directly taken up from the soil.  Evaluating efficiency of uptake and utilization is a couple steps down the road.  Amino acid fertilization could potentially provide another benefit over nitrate fertilization by reducing nitrate leaching.

 

Of course there’s a potential downside as well.  A quick Google search of ‘amino acid fertilizer’ reveals sites shilling all manner of concoctions for fertilizing plants; many of dubious value.  One of the first sites I hit proclaims that, unlike inorganic fertilizers, their product provides the 70 elements needed for plant growth.  Seventy?!  Well that’s close to seventeen.   Point is be prepared for an ever increasing barrage of claims about organic fertilizers.  There is no doubt that compost and similar organic sources can provide essential plant nutrients and effective fertilizer sources.  As always, however, be skeptical of spectacular claims and secret, proprietary ingredients and pay close attention to the cost of amino acids compared to conventional fertilizers.  There is some science here; clearly many plants have the capacity to take up amino acids directly.  Beyond that we’ve still got a lot to learn.

 

Gallet-Budynek, A., E. Brzostek, V.L. Rodgers, J.M. Talbot, S. Hyzy, and A.C. Finzi. 2009. Intact amino acid uptake by northern hardwood and conifer trees. Oecologia 160:129–138.

 

Ge, T., S. Song, P. Roberts, D.L. Jones, D. Huang, and K. Iwasaki. 2009. Amino acids as a nitrogen source for tomato seedlings: The use of dual-labeled (13C, 15N) glycine to test for direct uptake by tomato seedlings. Environmental and Experimental Botany. Volume 66: 357-361.

 

Kielland K, J. McFarland, and K. Olson. 2006. Amino acid uptake in deciduous and coniferous taiga ecosystems. Plant Soil 288:297–307.

 

T. Näsholm and J. Persson.  2001. Plant acquisition of organic nitrogen in boreal forests, Physiol. Plant 111: 419–426.

Friday mystery photo

Today’s photo is courtesy of Photoshop technology.  I’ve edited the damaged area so you can’t see what caused, or at least contributed to, the damage:

Now before you complain that I’m cheating (which I am!) keep in mind that what I edited out could have been removed before you were asked to diagnose this injury.  I will tell you that it’s not due to pests or disease.  As is so often true in real life, there could easily be multiple correct answers.  On Monday I’ll provide an untouched photograph and rail against the all-too-common practice that can cause the damage.

Have a great weekend!

Atrazine, The news, And the reality

A paper was recently published in the Proceedings of the National Academy of Sciences which discussed the dangers of one of the most commonly used weed killers in the United States, atrazine.  This paper was written by Tyrone Hayes and colleagues and was immediately embraced by the media because it showed something scary (which the media loves — in case you were wondering).  In a nutshell this study showed that frogs were changed from males to females when they were exposed to relatively small amounts of the herbicide atrazine.  The next day in class I had a student come up to me and ask me about it and what I thought.  I gave him my short answer (class was about to start).  Here’s the longer one, but first I want to present you with some notes which will be important as we proceed.

Science does not provide values, instead it is a tool to use with your own personal value system.  Some people may put a high value on cheaper production of important food crops such as corn, while others may put a high value the absence of potentially dangerous chemicals.  That doesn’t matter to science.  Remember that — science doesn’t give a poop what you care about.  Furthermore, science doesn’t care what past experiments have found — what one researcher finds another may not find.  Who knows why?  That’s just the way things happen.  On with the story.

Atrazine has been around since 1959.  It’s a preemergent herbicide (which means that it kills weed seeds as they germinate) used on a variety of crops, but most frequently on corn.  One of the advantages of atrazine is that it works extremely well in no-till growing systems which are used to reduce erosion.  Another advantage of atrazine is that it’s cheap.  Generally atrazine is considered to have a low toxicity (lower than caffeine for example).  Additionally, though there is some data out there showing that it may cause cancer, this is grossly outweighed by data demonstrating that it isn’t carcinogenic.  But there is data showing that atrazine is a hormone disruptor potentially affecting such hormones as estrogen and testosterone — and this effect is generally considered real — in other words not many scientists dispute it.

Over the years this hormone effect has been seen as a Bad Thing, but not bad enough to warrant banning this useful herbicide.  Then along came Tyrone Hayes — and he started looking at how atrazine affected frogs — despite the recent news surge he has been doing this work for a long time (about 10 years) and has published much of that work.  In a nutshell he is showing that atrazine, and to some extent other chemicals, cause hormone problems in frogs, particularly male frogs.  Sex change and/or hermaphroditic frogs ensue!  Unfortunately (or fortunately depending on how you look at it) other researchers have not been able to show the same things — at least not it the dramatic way that Dr. Hayes has (I’m not implying that they haven’t found problems with atrazine — they have — Dr. Hayes findings just tend to be more dramatic.  Speaking of which, if you ever have the opportunity to see Dr. Hayes give a talk GO!  He is an amazing public speaker and his slides and words make his findings even more dramatic).  There is little to no direct evidence that hormone disruption caused by atrazine is currently affecting humans though many news sources are trying to draw that link.  Indirect evidence is pretty weak too — but not nonexistent.  The European Union banned atrazine in 2001.  Should we follow?

My value judgement follows — yours might be — in fact it probably should be — different.

Here’s what I think.  Ban atrazine, or at least regulate it more tightly.  Why?  Because there are many weeds resistant to it (that’s what happens to old herbicides…). Because there are options which are safer for our ecology (though they are somewhat more expensive). Because this stuff is showing up in groundwater at rates higher than what we’d like to see, and these concentrations will probably continue to rise — a direct result of using the stuff for so many years.  Look, we don’t need to cut farmers off from this stuff right now, lets start a phase-out program and get rid of it over the next five years.  Why not?  If we NEEDED it to produce crops I’d probably be on the other side of the issue, but we don’t, so I reside firmly on the “let’s be cautious about this” side.

You say tomato, I say phytochrome

Yesterday I got an interesting email about a new product – a Tomato Automator.  Briefly, this square, red plastic disk slips around the stem of a tomato plant to suppress weeds and pests.  Most intriguingly, we’re told that the color “triggers a natural plant protein that makes tomatoes mature faster and product more fruit.”

Given this is a red product, it’s likely that the protein referred to is phytochrome (literally, “plant pigment”).  Phytochrome activity is maddeningly complicated to explain, so we’re going to keep this simple and refer (somewhat inaccurately) to “active” and “inactive” forms of phytochrome.  The active form of phytochrome exists when red light is predominant and encourages leaf expansion, chlorophyll development, and other characteristic of plants growing in full sun.  In contrast, the inactive form of phytochrome occurs when red light is reduced, either at night (when there’s no light) or in shaded conditions, where far-red light is predominant.  (Far-red light occurs just outside our range of visual perception but is absorbed by phytochrome.)

From a practical standpoint, this means a plant can “tell” whether or not its light environment is limited: both red and blue light are absorbed by chlorophyll, so a low level of red light means poor photosynthetic conditions.  Under such conditions, “inactive” phytochrome causes many plants to become etiolated (have abnormally long stems) in an attempt to outgrow the shade before it starves from lack of carbohydrate production.  In addition, this photosynthetically-poor light environment can also increase fruit set by redirecting resources to seed production rather than foliage  – perhaps a plant’s last effort to reproduce before it dies.

OK, now onto the useful application of this information.  Several years ago researchers investigated that effect of different colored plastic mulches on tomato production.  Again, to keep this simple we’ll just focus on the effect of red mulches.  It’s pretty much agreed that red plastic mulch reflects both red and far-red light, increasing not only red light but paradoxically the relative levels of far-red light.  Theoretically, this shift would cause tomatoes to put more resources into fruit production, and indeed some studies found this to be the case.

Unfortunately, the phenomenon is not consistent throughout repeated field studies.  Some of the other confounding factors are soil temperature (warmer temperature = more growth), insect and disease pressure (both decrease tomato production and are variably influenced by mulch color), and the fact that ethylene production (the plant growth regulator responsible for fruit ripening) is not controlled by phytochrome at all.

So are Tomato Automators worth the trouble?  Probably not, especially if you have many plants requiring many automators.

I’m Saving Myself for Pollination

Let’s take a very brief respite from the socio-religious implications of science, soil testing, and compost tea to ponder a more lighthearted topic. I need a bit of a morale-boost.

You: “O.K. Holly, Spring’s allegedly coming…how about a closer look at some wildflowers?”

Me: “Done!” (fingers snapping)

For a short time in March, forest floors across Eastern North America can be absolutely littered with a multitude of sparkling white flowers.  This very cool little plant, Sanguinaria canadensis, is one of the first wildflowers to emerge in the spring and colonizes deciduous and mixed woodlands.


Flock of bloodroots, open for business at the fabulous Mt. Cuba Center.

A member of the Poppy family, Sanguinaria is a monotypic genus; that is, there’s only one species.  Commonly known as Bloodroot –  mostly.  However, S. canadensis is also known as (and I quote):   Bloodroot, Red Puccoon, King Root, Red Root, Red Indian Paint, Ochoon, Coonroot, Cornroot, Panson, Pauson, Snakebite, Sweet Slumber, Tetterwort. Large Leaved Sandwort, Large Leaved Bloodwort, plus whatever else Aunt Minnie “knowed it by”.

As one of the first wildflowers out of the ground, it’s still darn cold when the Bloodroot flower appears, and they’re quite protective of their private parts. The one leaf emerges at the same time and cups around the flower, helping to protect the fragile blossom from wind, rain, and snow. The petals also close up at night to save the pollen,since in most locations it’s so cold that few insects, save the occasional fly or beetle, are out and about. And as a last resort, they can just “do it themselves”, better described as self-pollination.


I have been pollinated! Victory is mine!

If you break off a stem or piece of the root, out will ooze a reddish-orange juice, hence the common name.  It’s been prescribed for myriad conditions by Native Americans and herbal practitioners.  One of the more interesting properties is that the sap is an escharotic – it kills tissue. Ironically, according to herbal lore, to draw love to you, wear or carry a piece of the rhizome. If attempting this bit of magic, maybe it’s best not carried in one’s pants pocket.

Art, Science, and Faith

First of all, who we are and what we do.  All of the Garden Professors are in the business of the science of Horticulture.  What’s Horticulture?  The standard definition of Horticulture is the art and science of tending a garden.  Horticulture is clearly more than science but science is the foundation and underpinning.   For anyone that needs convincing that Horticulture is an art as much as a science I suggest the following exercise.  Go to a major research university and wander through their Botany or Plant Biology greenhouses. Observe the plants.  They look like crap.  The people working there are on the cutting edge of plant science; they sequence genes, they elucidate biochemical pathways but they can’t grow a plant to save their lives.   Now wander through the Horticulture greenhouse; plants are thriving, flowers are blooming.  What’s the difference?  The horticulturalists not only have the science, they have the art.  There is no denying that art and intuition play a role in growing plants, especially in ornamental horticulture where we deal with hundreds of species and cultivars, each with its own subtleties and nuances.  But as educators, especially public funded educators, how do we teach intuition?   It’s very difficult.  What we teach are principles developed through systematic scientific inquiry.  How do we know there are 17 essential elements needed for plant growth?  Repeated experiments over the years.  And our knowledge continues to evolve based on the scientific method.  I’m old enough that I learned 16 essential elements as an undergrad; the need for nickel by some plants had not yet been established.  As extension educators our role is to disseminate science-based information.  For some of us that phrase is even in our job description.  We can try to impart our experience and intuition but it’s a difficult thing.

It can be especially difficult when we deal with alternative systems for which a long-term knowledge base may be lacking.  Despite perceptions to the contrary, we are not apologists for the status quo.  Overuse and misuse of pesticides and fertilizers are rampant, especially in ornamental horticulture.  A lot of our current research and extension programming deals with reducing water and nutrient usage to reduce run-off and to reduce leaching.  I spend a lot of time telling growers things they don’t really want to hear.  How do we know growers are potentially impacting water resources? Because we and others have done the scientific research.  We’ve set out plots, we’ve fertilized, we’ve sampled leachate, we’ve measured run-off.  And we’ve conducted extension programs teaching growers that they can back off fertilization and irrigation rates without reducing crop growth.

Where we get concerned is that some assume or take on faith that because a nutrient source is ‘organic’ or ‘natural’ it’s automatically better or safer for the environment.  Is the nitrate from Chilean nitrate less likely to cause blue baby syndrome then nitrate from ammonium nitrate?   Dr. Corey Reams developed his principles as revealed to him through divine revelation.  Unfortunately most of us are not blessed with such experiences.  Instead we rely on systematic scientific investigation to develop knowledge that we share with our clients.  Personally I do not believe that faith and science are mutually exclusive.  Some of the most brilliant scientists I have met in my career have been people of deep and abiding faith.  But we need to keep each in its context.  Science is knowledge gained through systematic inquiry.  Faith is a belief system.  The central tenets of most Christian denominations are stated in the Nicene Creed which begins, “We believe in one God…”  Note it doesn’t start “We know…” or “We can prove…”  In their liturgy Catholics, “proclaim the mystery of faith; Christ has died, Christ is risen, Christ will come again.”  Not only can they not prove these things they celebrate the fact that it’s a mystery.  Faith does not demand proof.  Science does.

Friday puzzle solved!

Lots of brainstorming over the weekend, and all the answers were legitimate.  A few people came close with the observation that the roots looked like they had grown over something.  And that’s exactly right:

This is a great example of nurse log decomposition.  When the tree on the right first began growing (and it could have been decades ago), it sent lateral roots out, over, and around the nurse log to reach the soil.  As the nurse log degraded, the tree’s roots were left high and dry, outlining the girth of the original log.

Does this natural example have application in managed landscapes?  Absolutely!  As several of you pointed out, removal of soil or organic matter by erosion or decomposition can leave woody roots exposed.  If these roots are injured by feet or tools, they can lose their bark and become open to disease or pests.  These are the structural roots of the tree, and if their stability is compromised, so is that of the tree.

(Though this tree has had some injury to its roots (probably from hikers), it’s unlikely to fail as it’s pretty small. )

Friday puzzle

Finally – something else to do rather than post to the IAL blog!  On to today’s photo (and I apologize for its blurriness).

The tree in this photo is alive, and as you can see has structural roots perched well above the soil.  How might this have happened?  There are multiple possibilities.  And secondly, is there a negative impact on the tree, and if so, what?  Answers and another photo on Monday!

Have a nice weekend!