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Most of us were taught from an early age to trust doctors (I mean the medical kind).  They’re supposed to be smart, committed, and loving, and most of the doctors I’ve had over my life have fit that mold.  And Earth, what an awesome name!  It makes me think of dark, warm, rich soil in the spring.  Damn it makes me feel good!  So it’s no wonder that some clever marketer thought up the name Dr. Earth and slapped it on a bunch of organic products, because hey, if you can’t trust Dr. Earth who can you trust?  When I see a Dr. Earth package I want to buy it!  I mean look at it:

How can you not trust this guy?  But as most wise shoppers have learned over the years, whenever you purchase a product you should look at the ingredients to see what you’re buying.  This product includes Probiotics — microbes which are probably dead when you buy the fertilizer — or which may not even be compatible with your soil.  It is a “balanced” fertilizer meaning it has equal parts nitrogen, phosphorus and potassium — which means too much phosphorus and potassium.  And finally, while it does have a number of good renewable ingredients, it also contains bat guano and rock phosphate, two ingredients which are non-renewable and which damage the earth when they are mined.

You can’t judge a book by it’s cover, or, apparently, a fertilizer, by the cute farmer-looking guy on the front of the package.

Ok, ‘Hot’ might not be exactly the right word, but winter in the Midwest has certainly been warmer than average this year.  I did a little trolling around on Michigan State University’s Automated Weather Network website, which has been logging temperatures and other weather variables around the state for the past 15 years and compared our current winter here in East Lansing to recent years.  Since the middle of December our average daily temperatures are 5.2 deg. F above the previous 15-year mean.  The departure from the 15-year mean is even greater (+5.6 deg. F) when we look at minimum temperatures. 

15-year average Minimum daily temperature and Current-winter daily minimum for East Lansing, MI.

Minimum temperatures are especially important when discussing winter injury to landscape plants since extreme low temps (and the conditions immediately preceding them) are often responsible for many of our winter injury problems.  With a generally mild winter and only a few, brief temperature dips below average, one might expect that we will see few winter-related plant problems this spring.  However, prolonged exposure to temperatures above average means that plants are beginning to deharden early.  We see several signs of this already; such as witch-hazels blooming in protected locations and sap in maple trees running 2-3 weeks ahead of normal http://www.michiganradio.org/post/michigan-maple-syrup-producers-say-season-extra-early-year

February 28, 2012. Witch-hazel in bloom on MSU campus.

While other trees and shrubs may not provide the same outward signs, they are progressively becoming less cold-hardy by the day.  Unfortunately, temperatures, like the stock market, rarely move in a straight line. Here in mid-Michigan, temperatures in the single digits are possible throughout the month of March.  Given the preceding mild conditions, a sudden, severe cold snap still holds the potential to cause considerable damage to developing buds on trees and shrubs.  This type of late from damage may be evidenced by shoot die-back, bud-kill or death of newly-emerging shoots.  As always with winter injury, the final result won’t be known until late May or early June. 

I ‘like’ American Forests page on Facebook so I receive their periodic updates.  One item that caught my eye recently was a profile article on Dr. Greg McPherson, who is an urban forestry researcher with the USDA Forest Service in Davis, CA.  Even if you don’t recognize the name, if you have even seen any statistics on the economic and environmental benefits of trees in cities (energy conservation, carbon sequestration, etc), they probably cited information for McPhereon’s studies, either directly on indirectly,

http://www.americanforests.org/magazine/article/forest-frontiers-greg-mcpherson/

What really made me say “Amen, brother!” in the American Forest piece was McPherson’s response to the question, “What’s the biggest issue in urban forestry today?”  His reply, “Moving from the tree-planting paradigm to the tree-performance paradigm.”  Let’s face it, tree planting, for want of a better term, is sexy.  It’s relatively easy to raise money or get politicians to show up for a tree planting event and throw a few scoops of dirt with a ceremonial silver-plated shovel while the local media cameras are clicking.  

Image: Stephen Simpson/London News Pictures

But who is going to get excited about maintenance pruning? Or developing workable tree ordinances?  Or a pest management program?

Image: Susan Lesch

I’ve participated in various tree planting programs and it always gives me mixed emotions to hand out tree seedlings to second graders.  I’m glad they’re excited about getting a tree but also realize most of the seedlings that those 7-year-olds are running with will have the same lifespan as a goldfish that comes home in a plastic bag from the county fair.  Does this mean we should ban tree giveaways or planting events?  Of course not. Even if only a few seedlings survive the grubby hands of second-graders, that’s a plus and building their awareness of trees and their environment is the bigger issue.  But we also need to build public awareness of what it takes to maintain the urban forest and accrue all those benefits on the long term.  And most of those activities don’t make good photo ops or video clips for the local TV news.

In some places, we’re starting to get the message.  Here in Michigan our Department of Natural Resources awards Community Forestry grants.  The program will fund various activities but many grants are for tree planting.  If the application is for tree planting, the applicant must include a description of the maintenance practices that will be used to ensure the long-term success of the planting – forcing applicants to think about what happens after the trees are planted.  In addition the program also requires that applicants plant a diversity of species to help reduce issues with monocultures.  Small steps, but the ones we need to take to move from the tree planting paradigm to the tree performance paradigm. 

According to a post by Paul Tukey on safelawns.blog, a recent French study which was published in the Journal of Applied Toxicology shows that corn which has been genetically modified to produce the caterpillar toxin Bt is poisonous to humans.  Furthermore, so is roundup.

Ladies and Gentlemen, we’re screwed.

The rapture is coming.  The true believers who shun conventionally produced food and eat only organic, non-GMO will be saved.  Those who don’t, well, they’re all as good as dead so don’t even bother worrying about ‘em.  Brothers and Sisters, change your ways now while there’s still time!

The end will come, not in the form of fire or water, but instead kidney failure and it will come as punishment for playing with Nature.  By messing around with that which Nature has wrought we have inadvertently created a subtle beast that now lies quietly in our bloodstream poised to destroy us.  We are the architects of our own doom and can only hope that those who survive the destruction mend their ways to bring this world back to its GMO and pesticide-free ways.  It’s our only hope.  

OK, the above statement is more than a little over the top.  Hopefully you realized that as you were reading it.  Here’s the real story.  Let me start with Paul Tukey.

I’ve read a lot of what Paul Tukey has written.  He’s a guy who’s very concerned about the amount of poison that we spray on our crops and our lawns and, to be honest, I admire his resolve, and I agree that we overuse pesticides – and to go a step further it’s people like him who are going to get people excited about reducing pesticide use and are going to make a difference in the backyards of America.    

BUT (you knew there would be a but didn’t you?) he has a habit of over-interpreting what the studies say and/or passing along information that does the same.  Usually it’s not too bad.  For example, this article about Round-up is a bit over the top and is based more on the beliefs of one scientist who is considered an extremist rather than on our best scientific data, but at least it acknowledges the fact it might be wrong.  It’s the kind of article that I don’t like, but not one I’m going to get up in arms about because then I’d be constantly up in arms and probably end up suffering from chronic migraines – there’s just too many articles like this for me to worry about all of them.

The article that I began this post discussing is different because it says, and I quote “genetically modified corn containing the genes for Bt (Bacillus thuringiensis) is toxic to humans” and then goes on to say the same thing about Round-up.  The implication is that the study which was conducted shows without the shadow of a doubt that we’re killing ourselves by eating genetically modified crops which have the Bt toxin and/or have Round-up used around them – at least I think that’s the implication.  If any of you think I read it wrong please let me know.

The idea that this study shows that we’re hurting ourselves with genetically modified crops is ridiculous (please be aware that I’m talking about this particular study — there certainly could be others in the future that change my mind).  Why you ask?  Let me count the ways.

1. We eat Bacillus thuringiensis all the time.  It’s a naturally occurring bacterium which is often present in food and is cultured as an organic pesticide which is likely to be present at some concentration in organically produced crops sprayed with it.  If you think that avoiding genetically modified foods will keep you away from it you’re sadly mistaken.
2. This study tested the effects of Bt and Round-up on a strain of kidney cells.  Hardly any Bt and Round-up gets to kidney cells even if you eat or drink them – there are just too many barriers to cross before reaching the blood stream (But it is important to note that some certainly does – just very, very little – One article I found showed a level of about 0.2 nanograms Bt/milliliter blood and about 75 nanograms Round-up/milliliter blood in a population in Canada). 
3. This study artificially placed Bt and Round-up in with kidney cells in a test tube.  Obviously nothing like a natural environment.  Try the same thing with coffee or dish soap at the same concentration and I bet you’ll see worse damage to the cells.         
4. Just to get picky, kidney cell line 293 was used.  Look it up on Wikipedia (look up HEK 293) this IS NOT an appropriate cell line to be testing poisons on.

Long story short — the article cited really doesn’t reveal much abo
ut how safe or dangerous genetically modified crops are.

There are a lot of great products out there for controlling insect pests without using pesticides.  Some of the best include insect diseases or predators which will attack the pest and not beneficial.  For example, there are wasps that kill mealybugs and nematodes that attack grubs.  Both of these products are pretty effective.  That said there are also some products that just don’t work that well.  One of them is known as milky spore disease.

Milky spore disease is a bacteria that infects a variety of different scarab beetles – of which the Japanese beetle is one.  It isn’t a disease that we imported from Japan – it’s actually one that was found here.  Because this disease affects the Japanese beetle and it isn’t a pesticide per se people get very excited about it.  The problem is that it just doesn’t work that well.  Sure, it will offer some control, but not much.  Probably somewhere less than 20%.  Furthermore, most people use it in hopes of reducing their adult beetle population, but adult beetles come from all over, perhaps even miles away, so killing the beetles in your soil doesn’t in any way guarantee that you’ll be controlling the adult beetles eating your roses.

Now if you want to encourage your township to try milky spore disease that might work.  Spread over larger areas milky spore will have more of an effect for obvious reasons.  But placed on one yard, it’s just not going to do that much.

As part of my ‘other duties as assigned’, I have taken on an assignment to develop fertilizer prescriptions for landscape trees and shrubs based on soil samples submitted by homeowners to the MSU soils lab.  This has gotten me immersed in two sets of conflicting literature. 

On one hand is a raft of extension bulletins and ISA guidelines on tree fertilization, which typically suggest adding 2-4 lbs of nitrogen (N) per 1,000 sq ft of ground area – in some cases up to 6 lbs of N per 1,000 sq ft (Rose 1999).  To put that last number in perspective, that works out to 262 lbs of N per acre.  A typical recommendation for corn in Ohio is 150 lbs of N per acre.  Landscape trees need more fertilizer than a field of corn?

On the other side are numerous landscape studies, and even some nursery field studies, that suggest landscape trees simply don’t respond to fertilization (Day and Harris, 2007; Ferrini and Baietto, 2006; Harris et al., 2008; Robbins, 2006; Werner and Jull, 2009). 

So, what gives?  I mean, we know trees need nitrogen to make proteins, enzymes, chlorophyll, and all that good stuff.  We rake up leaves and haul them away each fall; short circuiting the natural nutrient cycle.  Urban trees should be starving for nutrients and begging to be fed, yet don’t grow any better when we fertilize them?  There are likely several factors at work.  First, many of the widely circulated recommendations are based, at least in part, on rates that might be applied in production forestry or nurseries where maximizing growth is a primary objective.  Also, as Dan Struve (2002) noted in his review, some recommendations were based on poorly designed studies.   Or, as Dan Herms (2002) hypothesized, trees may be allocating more resources to defensive compounds. 

Another answer may be found in some of the papers cited above.  In many cases, foliar N levels of the control (unfertilized) trees were already in sufficiency ranges.  In other words, even without fertilizer the trees had enough nutrients.  Part of this is a recent emphasis on the question of fertilizing at transplanting.  Trees coming in from a nursery are likely to be pretty jacked up with fertilizer – often referred to as a ‘nutrient loading’ effect.  Trees can be pretty efficient at internal nutrient re-cycling, so this effect can persist for a few years after transplanting. 

So where does all this leave me on my homeowner recommendation?  For some elements, like potassium and phosphorus, we can base a recommendation on the standard soil test included in the program.  Unfortunately there is no simple indicator of soil N availability (see Scharenbroch and Lloyd (2004) for a thorough discussion).  Foliar samples would be the best bet but aren’t part of our testing program.  At this point, I’m leaning toward a simple visual assessment – Do the trees/shrubs look healthy and have acceptable color? (check yes/no).  If ‘yes’, don’t fertilize.  If ‘no’ add 1-2 lbs N/ 1000 sq ft.

Your thoughts?   

References

Day and Harris. 2007. Arboric. and Urban Forestry 33:113-121.

Ferrini and Baietto. 2006. Arboric. and Urban Forestry 32:93-99.

Harris et al. 2008. Urban Forestry and Urban Greening 7(3): 195-206.

Herms. 2002. Environ. Entomology 31:923-933.

Robbins. 2006. So. Nursery Assoc. Proc. 51:113-117.

Rose. 1999. HortTechnology 9(4):613-617.

Scharenbroch and Lloyd. 2004. J. of Arboric. 30:214-229.

Struve. 2002. J. of Arboric. 20:252-263.

Werner and Jull. 2009. Arboric. and Urban Forestry 35:252-262.

A follow-up to Linda’s post about a recent study in Arboriculture and Urban Forestry that indicated mulch may not reduce evaporation of water from soil as we generally assume and which suggested that landscapers may want to re-evaluate their mulching practices.  As Linda noted, we have some real concerns about this conclusion and believe that proper mulching of landscape trees and shrubs has well-established benefits.

First, I don’t question the results present in AUF article.  As my grad students frequently hear me say, the data are the data.  But we need to bear in mind the paper is looking at one aspect of one of the impacts of mulching.  As Linda notes there are plenty of data to suggest that mulching does conserve soil moisture and she included some data from one of my studies which demonstrated this.  But there are other benefits to mulching beyond improving soil moisture.  I’d like to mention two here; one is a practical observation, the other is based on data from another study.

Preventing lawn mower blight and string trimmer trauma
From my observations and experience, one of the biggest and perhaps least appreciated benefits of mulch is keeping mowers and weed whips at bay.  I’m not aware of specific data, but damage by trimmers and mowers has to be near the top of the list of causes of mortality and long-term damage of new landscape trees.  A mulched zone around trees provides a buffer and simplifies maintenance operations. It’s an easy, simple and effective way to eliminate a major cause of tree distress.  A no-brainer.

Young, thin bark is no match for mowers and trimmers

Mulch protects trees and simplifies maintenance operations

Reduced soil temperatures
We conducted a trial a few years ago to look at the impacts of plastic mulches to improve establishment and early growth of Christmas trees. http://www.hrt.msu.edu/assets/PagePDFs/bert-cregg/cregg-et-al-2009.pdf  In a bit of serendipity we added a treatment at the last minute because our research station had some leftover wood chips from another project.  The trees mulched with wood chips were not irrigated but grew almost as much as trees in the plots that were irrigated.  What was especially impressive was the insulating effects of the wood chip mulch.  We installed probes to measure soil temperature 2” below the soil surface that we logged continuously.  During a July heat wave we found that soil temperatures were up to 10^oC (18^oF) cooler on the wood chip mulch plots than on the bare-ground plots.  Reducing soil heat load has profound implications for reducing root respiration and improving overall root function.

Soil temperatures were continuously logged on bare ground plots (foreground) and plots with wood chip mulch (background)

Soil temps peaked at around 38C (100 F) on bare ground without mulch (green dots);  max. soil temps were about 28C (82F) with wood chips (purple squares).

As Linda noted in her comprehensive review article, mulching has a myriad of benefits for landscape trees and shrubs.  It is important that we continue to look at all the various aspects of mulching and understand how to maximize the benefits (or reduce negative impacts) of mulching but in doing so it’s important to not lose site of the bigger picture.  While individual studies may yield conflicting data, on the whole, the preponderance of evidence and practical considerations come down strongly in favor of mulching

I’m no global warming apologist.  I do think it’s happening.  I think the new USDA map supports that it’s happening.  I also think that humans probably have something to do with it since we cut trees and burn fossil fuels which release carbon dioxide, a greenhouse gas, into our atmosphere.  That said, I’m not convinced that the carbon dioxide produced by people is as big a player in global warming as we’re being led to believe, or that the world is about to become a living hell because of it.  Still, I don’t know if I’m on board with this article published in the Wall Street Journal last week.  Sixteen scientists with diverse backgrounds basically encouraging us to ignore carbon dioxide emissions for awhile. 

Look, even if global warming is a red herring, carbon dioxide isn’t the wonderful universal fertilizer claimed by this article.  Increased carbon dioxide does encourage the growth of some plants, others don’t benefit as much, meaning that some weeds will become more competitive with crops as carbon dioxide levels increase.  These crops include such things as rice and corn.  Furthermore, increased carbon dioxide means that more nutrients will need to be pulled from the soil by plants which are trying to grow faster — kinda like how you need more gas (nutrients) for a faster car (faster growing plant).  So that’ll mean more fertilizer used for crops, which will be used at about 30% efficiency (about 70% of what we apply to crops never gets to them) and the rest will go into the air or into the water as pollutants. 

To me, the carbon dioxide issue isn’t, and never was, about global warming — because we can’t prove how much it does to climate change.  The issue is crops and ocean acidification (which I haven’t gone into here) because we have very good data in these areas as they relate to the negative effects of increased carbon dioxide levels.  We need to rethink our fossil fuel use.