Friday puzzle answer

So many interesting answers to Friday’s puzzle – thanks to all of you for putting out the effort!  It most certainly is an abiotic problem – but was it temperature, suggested by Deb?  Water, suggested by Foy, Gayle and Ed?  Light, suggested by Nancy?  My plan was to have an extensive soil test run to address the possibility of pollution (suggested by Jim, Heather and Paul), except we discovered the source of the problem last summer when we finished digging our pond:

 

As you can see in this photo, we have solid clay about 12″ below the surface.  (And I do mean solid.  I’ve kept lumps of the stuff to take to seminars, so when people say “I have clay soil” I pull this out and ask if this is what they mean.  Usually not.)


So in this area of our yard we have a perched water table: the water percolates through the topsoil, hits the clay, and spreads horizontally.  When we had turf in place, it tended to keep the upper few inches relatively dry, which allowed the dogwood roots to survive.  When we took out the turf and covered it with wood chips (to conserve water!), the soil became saturated nearly year round.  We dug out the tree a few weeks ago, and this is all that remains of the root system; the rest of the major roots had rotted away:


We’ve replanted the tree in another area of the yard with much better drainage, and we’ll keep track of its establishment and leaf size.  I think it will recover, as new roots will emerge from the main root mass.

(Paul, thanks for the kudos on the fence design!  My husband built this, and he’ll be pleased to see your comment.)

Friday quiz time!

Now I could have sworn I’d posted this puzzle before, but after searching through all the previous postings I can’t find it.  Here it is.

I planted this Cornus kousa in 1999 (removing the burlap, clay, etc. prior to installing).  We removed the turf (still attached to the $(%&$ plastic mesh) and planted the tree in the existing soil.  The first photo was taken in 2004, and the second was taken in 2007:

 

Here are some specifics about what was done to the landscape during this period: we replaced all the turf with wood chips and put in the fence as shown.  There was no impact on structural roots from either of these activities, and fine roots were affected minimally when we dug post holes for the fence.  The turf was simply allowed to die back in the summer (hot summers do that here in Seattle) and then topdressed with wood chips.  There were no chemicals applied, nor was there any soil disturbance.

It was about 2007 that we noticed the leaves were substantially smaller than previous years.  The leaves are sparse and small, but they don’t become chlorotic or necrotic during the summer, nor does any part of the tree suffer more than any other.  This phenomenon has continued until this year, when we finally dug it up and moved it elsewhere.

So here’s the question:  why did this tree start swirling down the mortality spiral?  As always, there may be many legitimate answers – but I’ll show you the actual reason on Monday!

Enjoy your weekend!

Edgeworthia!

Some of my favorite plants are those that “do something” when little else is.
Do we really need more June-flowering perennials? No!
Well, yes. Never mind.

Edgeworthia chrysantha – “Paperbush” is the common name – is a deciduous suckering shrub , native to China. It usually maxes out around 4′ to 5′ tall and as wide.  The large, matte bluish-green leaves resemble those of Magnolia virginia in shape and are also a bit silvery on the underside.  But that’s not what we’re here for…

An oooh-aaahhh-worthy specimen at the Hahn Horticulture Garden, Blacksburg, VA.

Furry, silvery flower clusters dangle like earrings from the cinnamon stems throughout the winter, getting larger by the month.  

Then by late February or March, they open up, all golden and waxy, emitting a light, sweet fragrance on sun-warmed days.


Blooms at Pine Knot a few Springs ago…

Edgeworthia is ideal for the deciduous woodland environment. Hellebore specialists Dick and Judith Tyler of Pine Knot Farms (Clarksville, Virginia), situate theirs among drifts of spring bulbs and, of course, Hellebores. It’s a soul-stirring sight in March.

I believe the hardiness of Edgeworthia may be underestimated, especially if you go to a little effort to select the right microclimate.  Dr. Dirr lists it as Zone 7 to 8(9). Having enjoyed them at the JC Raulston Arboretum during my doctoral work at NC State (Raleigh, North Carolina; Zone 7b), I found Edgeworthia was little-know here in the Blue Ridge (solid Zone 6, alledgedly 6a).  We ordered some in for our Garden and Hort Club’s 2007 plant sale held in late April – despite my pleading and mark-downs, they didn’t generate much interest from shoppers as they were out of flower. We planted the left-overs in a fairly protected position on the North side of our garden pavilion, and they’re thriving. Snow was heaped up around them throughout January and February and we’ve gotten well into the single digits complete with howling winds a few times.  Despite this rotten winter, they look better than ever, ready to burst into bloom any day now.  Readers, please weigh in: Had any success with it in Zone 6?  And why isn’t this fabulous thing more prevalent in the trade? 

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.