Category: Diversions

Invasives! Natives! No, wait, biodynamics

Just had to get your attention there.  We’ve had a great discussion over native and nonnative plants over the last few weeks.  I’m going to completely switch gears and move on to another topic  – biodynamics.

If you’re not familiar with this term, let me refer you to my online column here.  Biodynamics is a set of agricultural practices based on a belief system, not science, but is an increasingly popular approach, especially in the wine industry.  (You can read a discussion of biodynamics in the vineyard in The Skeptical Inquirer here.  This article is engaging as well as accurate – my column is pretty dry by comparison.)

Biodynamics is steeped in mysticism and includes special preparations that are used to treat soils and plants.  Preparation 500, for example, is created by mixing water with manure that has been packed into a cow’s horn and buried for a set amount of time.  Other preparations are more gruesome, requiring a stag’s bladder or cow’s intestine.  A whole certification process has emerged in support of these practices.

While it may be easy to dismiss these practices, it turns out that biodynamic farms or vineyards are generally healthier than conventional systems.  Does this prove a mystical force at work?  Not at all.  Biodynamic systems are also organic – using all of those good practices (low or no till, reduced pesticides, reduced fertilizers, polyculture, etc.) that have been demonstrated to be effective over decades of research.  When comparisons are made between biodynamic and conventional systems, the impact of organic practices are hidden.

The few scientific studies that have compared biodynamic to organic systems – in other words, specifically testing the effectiveness of special preparations – have found no repeatable, significant differences.

Why do I even care about this?  Well, it’s because it’s pseudoscience.  It’s a practice that takes on the mantle of science, but doesn’t stand up to repeated scienific testing.  Belief systems can’t be tested – even the inventor of biodynamics asserted that his methods were “true and correct unto themselves” and didn’t need to be tested.

Apparently simply being organic isn’t sexy enough anymore.

Pop Quiz!

Bet you weren’t expecting this on TUESDAY, eh?
Heh, heh.

Situation:  these photos are from a grad student project.  We wanted to create, observe, and record nutrient deficiency symptoms, so we grew the plants hydroponically in a made-from-scratch nutrient solution, containing everything except one particular nutrient. There were 12 separate batches of solution, one missing each essential mineral nutrient (N,P, K, Ca, Mg, S, Fe, Mn, Cu, B, Mo, Zn – couldn’t exclude Cl as it’s too common in salts).  As my research interest is herbaceous perennials, some common perennial taxa served as our victims, er, subjects.

Here’s the set up for the Verbena ‘Homestead Purple’ experiment – rooted cuttings were placed in the little buckets and secured by the lids. The nutrient solution was constantly aerated. For most elements, symptoms appeared between two and four weeks after the start of the project. Symptoms, depending on the elemental deficiency, included chlorosis (yellowing) of old or new leaves, leaf curl, speckling, stunted growth, and in one case, some excessive growth.

Below are results from day 42 of the study. We lifted the lids, hanging-basket style, so we could examine the roots. The control (received a complete nutrient solution) is on the left; Rapunzel there, on the right, lacked a nutrient. Quiz question:  What element was missing in this particular case?  What made you come to this conclusion?

Hint: If you have a rudimentary knowledge of garden fertility, be it veggie or ornamental, you can probably figure this out.  I’ll go ahead and rule out the pesky micronutrients.


(L) Control: received complete nutrient solution            (R) Deficiency solution

A thought about Invasive Plants

Recently there was an article published in the journal Science (widely considered one of the most prestigious science journals in the world) by two professors who I knew while I attended college in Pennsylvania (Franklin and Marshall College — Anyone ever heard of it?).  I found this article particularly interesting because it explained how the beautiful Pennsylvania scenery that we assume is natural was actually created over the course of three hundred years.  Saw mills and dams changed water flow patterns — those pretty streams that flow through the Southeastern PA (and nearby areas) that I grew up in aren’t natural at all.

Of course this is just another thing that we’ve done to make this country different from what it was when people first came here.  We’ve also farmed the heck out of the land, built large industrial areas and, on top of that, there’s the issue of global warming (which, for the sake of this post, we’ll assume is caused by humans), increased carbon dioxide in the air, decreased top soil and forest land (mostly because of the farming), and a general increase in soil, water and air pollutants.

So, with all that said, It seems to me that we’ve done a lot of things to change the environment.  With all that we’ve done why are we so upset when some plants, which we call “invasive” thrive in these settings?  It’s not their fault that they do well in the conditions we’ve created.  Sometimes I feel like we’ve built this great big smorgasbord of lutefisk (fish treated with lye — it’s pretty nasty) and then get angry when only people who grew up eating this type of fish come to the party.

I’m not trying to promote invasive plants — And I’ll be the first to admit that this post is oversimplifying the whole question of invasives — Still, it irks me sometimes that we aren’t more concerned about the environment where we plant our greenery rather than the plants themselves who, after all, are just feeding on the smorgasbord that we’ve created.

Friday puzzle solved!

Great discussion over the weekend, with some very astute observations.  If you looked at the brown needles under the tree in Friday’s picture, you may have noticed that some of them weren’t needles:

Not only was this tree planted too deeply, as several of you pointed out, but the burlap and twine were left intact.  It appears the nylon twine has already started to girdle the trunk, based on the trunk swelling just above where the twine is wrapped.

I’ve ranted about this practice already, so I’ll just sigh and move on to the first question – what directly caused the needle drop from the lower part of the tree?  It’s a young tree facing west so the lower half gets plenty of sunlight.  And though needle drop is normal with all conifers, the upper portion of the tree does not show the same drop with its interior needles.  My guess is that ethylene gas is responsible.

Plant roots under stress often release ethylene, a natural plant growth regulator more commonly associated with fruit ripening.  It also induces leaf drop, so as it percolates out of the soil it affects the lower leaves, but dissipates before it reaches leaves higher in the crown.  It’s a common phenomenon with over-watered house plants.

Thanks to all of you who participated in the diagnosis discussion – this is more fun than my 20 years of college teaching!

Friday fun!

It’s the holidays, but this pine tree is feeling anything but merry.  It was installed about a year ago.  While the upper foliage looks lush and green, the lower branches have no new needles and in fact the current needles are dropping:

This is a two part question:

1)  What might be directly responsible for the needle decline on the lower branches?  (Hint:  this is caused by the plant itself.)

2)  What might be the underlying stress causing the needle decline?  (Hint:  this is caused by by people.)

Additional photos on Monday will reveal all!

Salt solutions

Hopefully everyone got their filling of turkey and dressing over the long Thanksgiving weekend.  I used our unusually mild weather on Saturday to celebrate a time-honored tradition around the Cregg farm: The annual cursing of the tangled Christmas lights.

Turning the calendar over to December in Michigan means another Midwest tradition is just around the corner as well: The annual dumping of the road salt.  Although totals vary, at least one source estimates that road crews pour 8 million tons of salt on roads in the US each year.  The effects of this sodium chloride are readily apparent on our vehicles – in Michigan it’s rare to see a vehicle more than 10 years old on the road – and drivers of those older cars that remain can usually see the road pass under them through a rusted-out floorboard.  Of course all this road salt has profound implications for landscape plants as well.  Sodium chloride can damage plants in several ways.  Both sodium and chloride can cause direct toxicity, particularly from salt-laden spray drift from highways.  Salt in soils can cause osmotic stress resulting in drought injury.  Sodium in soils can displace potassium, magnesium, and other essential plant elements.  High levels of chloride in plant tissue can reduce cold hardiness and make plants more susceptible to freezing injury.  Suffice to say that salt is bad for plants.

So what’s a plant lover to do?  In general I advise a two-phase strategy of Selection and Protection for homeowners and landscapers that have to deal with heavily salted roads.  By Selection I am referring to planting salt tolerant plants (or at least avoiding salt sensitive ones).  The poster child for a poor choice in Michigan is eastern white pine, which is extremely intolerant of road salt.  Witness this planting at a rest area along I-96 between Lansing and Detroit.

Don’t you love to see your tax dollars at work?  Even a cursory look at a list of salt sensitive plants would have been a tip-off that that white pines and highways are a bad mix.  Most blog readers should be able to come up with a list of salt tolerant or salt sensitive plants for their area by Googling their way around the internet.  A couple caveats about these lists:  First, many are based on anecdotal experience, not hard data, so you may see inconsistencies between lists.  If possible, try to consult several sources and look for a consensus opinion about the plants you’re interested in.  Second, many recommendations are dated and include plants that may be considered invasive or no longer recommended for planting.  One list I just looked at included Russian olive (invasive) and green ash (no longer planted in the Midwest due to Emerald ash borer).

Another approach to reducing salt damage to plants is Protection.  Here I am referring to erecting a physical barrier to block salt spray or salt splash from reaching plants.  The most typical form of barrier around here is a wooden frame or fence covered with burlap or canvas.  Some people will actually wrap their evergreen trees or shrubs with burlap.  This may help against winter desiccation but does little for salt since the salt-saturated burlap will still be in contact with the foliage.  Obviously aesthetics go out the window with the protection approach but I’m noticing more and more people are willing to put up with a couple of months of looking at burlap to keep their plants looking thrifty the rest of the year.  In northern Europe some road systems will line their roads with pre-formed plastic barriers to reduce salt splash to adjacent vegetation.

What about alternative deicers?  This is a question I get frequently when I speak about salt and plants.  There are several things to consider about alternative (i.e., not sodium chloride) deicers.  First is the cost. All alternative deicers are more expensive than salt, some by a factor of 10 times or more.  This often limits their widespread use for highway departments.  Many road crews will use alternative products around bridges and other sensitive areas where they want to limit corrosive damage.  Alternative products may also be useful for smaller scale operations such as parking lots and walkways.  Secondly, many alternative deicers contain calcium and/or magnesium chloride.  These may even be marketed as ‘plant safe’ since they contain calcium and magnesium, which are essential plant elements.  The problem is the chloride.  Chloride is a plant nutrient but is only needed in minute amounts (a few parts per million). At higher levels it becomes toxic.

A study in Colorado found tree damage due to chloride near roads which were treated with calcium and magnesium chloride for dust abatement.   For safer alternative deicers consider chloride-free products such as calcium magnesium acetate.

In the meantime here’s hoping for a mild winter for everyone.

Friday puzzle answers!

Good speculation on the rhododendron leaf damage!  Jim in Wisconsin zoomed right in on the causes:  the first photo was taken on a year where we had an unseasonable freeze right as leaves were expanding, and the second was taken on a year where we had unseasonably hot weather as leaves were expanding.

In both cases, the ultimate cause of damage is lack of water in rapidly expanding tissues.  Once dormancy is broken, leaf and flower buds are highly sensitive to environmental extremes – they are expanding and are most sensitive to anything that interferes with water content.

During a freeze, leaf tissue water freezes, causing what’s called freeze-induced dehydration.  It’s not the ice that causes the damage, but the lack of liquid water in the cells.  Water freezes in the air spaces between cells, and osmosis draws water out of the cells into these intercellular spaces.  Eventually the cells more or less implode once they’ve lost enough water.

During a hot episode, the roots can’t keep the rapidly expanding leaves fully turgid, and again necrotic areas appear as a result of water loss through transpiration and cellular “implosion.”

So both of these problems are caused by a lack of leaf tissue water – and it’s impossible to tell from looking at them whether it’s from cold or heat or salt or some other stress that reduces water availability.

Bottom line:  keep track of seasonal abnormalities.  It will help you to correctly diagnosis problems that show up some time later.

Post-turkey puzzler

I hope everyone had a great holiday yesterday!  Since I am NOT a shopper, I’m avoiding “Black Friday” and posting another puzzle instead.

Consider this photo:

This is a rhododendron in my own landscape.  The photo was taken in July, though the damage on these new leaves occurred earlier than that.  In Seattle, rhododendron leaf bud break generally occurs in April.

Now consider this problem.  Same plant, different year – and actually a different problem!

So what caused this damage?

Explanations on Monday!

Advice Requested!

Greetings, all!

I am not a tree-care expert, having invested most of my mental capital into herbaceous plant stuff.  But I know enough to be dangerous: spiraling/strangling roots and narrow crotch angles are bad news. But at what point do they become “unfixable”? So I’m asking my illustrious colleagues and diligent readers (a.k.a “all y’all) for advice.

We have a lovely specimen in our campus Horticulture Garden…Acer ‘White Tigress’ – a hybrid between A. davidii and A. tegmentosum – also known as snake-bark maple.  Probably been in the ground for 18 years or so. Lovely buttery fall color, gorgeous stripey bark.

This tree, as we say in Georgia, “has more problems than a show dog.”

Scroll on down…


Bit of constriction there, mid-way up.


Some interesting crotch angles, too…

But here’s the kicker (I can hear Linda hooting it up from here…)

This poor gal is obviously a “what not to do” teaching tool.

But the question is:
Can this tree be saved? Discuss.

Friday puzzler revealed!

Lots of discussion about the mysterious white streaking on the hedge.  The pictures below show a little more detail than those on Friday:

As you can see, Jimbo was on the right track when he suggested the hedge might be near a parking lot.  But it’s the heat escaping from the engine compartments that’s been causing the damage. 

(I am now committed to find some good photos of urine damage by dogs, donkeys, or drunken frat boys!)