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Diagnosing plant problems

As an Extension Specialist working with nursery and landscape issues, I’m frequently called upon to troubleshoot problems with trees and shrubs in various settings.  Sometimes it’s residential or commercial landscapes, sometimes nurseries, sometimes Christmas trees.  So naturally I was intrigued when the most recent issue of American Nurseryman featured a cover story on diagnosing nutrient deficiencies in plants.  The article was written by Dr. Gary Gao, Extension specialist with Ohio State University.  The article http://www.amerinursery.com/article-7428.aspx is good and does a good job on covering the basics.  However, the introduction of the article also hit on one of my pet peeves – and what is the Garden Professors for if not to vent on our pet peeves.


The intro states:

"If you have a good understanding of the function of plant essential mineral elements and a familiarity with common symptoms, common mineral nutrient disorders can be diagnosed quite easily."

Maybe I’m just trying to justify my own existence, but I find diagnosing nutrient disorders anything but easy.  This article and countless extension bulletins and factsheets imply that you can diagnose nutrient problems simply by matching leaves from your tree or shrub to a photograph showing the same symptoms.  To which I have three words: Ain’t gonna happen.  For the upper Midwest, I can think of exactly two landscape nutrition problems that I would be comfortable diagnosing by visual symptoms; iron chlorosis in pin oak and manganese deficiency in red maple.  Beyond those two I would want information from foliar samples and soil tests, as well as some site information before concluding the cause of a plant problem.



The main issue, of course, is that plant problems rarely come gift-wrapped.  Nutrient deficiencies (or, rarely, toxicities) are often confounded with other site issues; poor drainage, excessive drainage, too much sun, too much shade, insect damage, diseases, salt exposure.  As I’ve said many times, it’s much rarer to find a ‘smoking gun’ than not.  Usually it’s process of elimination with a best case scenario where you can compare symptom and foliar analyses of  ‘good’ and ‘bad’ plants.  But I think we do a disservice to landscape and nursery professionals and homeowners to imply that identifying the cause of a problem is as simple as picking the right suspect out of a line-up. 

The people have spoken…

OK, the results are in for our reader poll to design a landscape tree transplant study here at MSU next spring.  And the winner is…er, I mean, winners are: Root ball manipulation and Fertilization at the time of planting.  Root ball manipulation drew 74.3% of the responses, Fertilization was chosen by 63% (voters could chose more than one favorite topic).  All other proposed topics were under 40% (Mycorrhizae – 37%, Crown reduction- 31%, Cambistat – 11.4%, Bioplex – 11.4%).  I will put pencil to paper and survey the trees and space available for a trial.  My initial thought is that we can do a 3 x 2 factorial experiment with 3 types of root-ball manipulation and 2 levels of fertilization.  Root-ball manipulations will include two popular recommendations: 1 – ‘shaving’ the root-ball to remove circling roots; 2 – ‘teasing’ the root-ball to untangle circling roots; and 3 control e.g., planting the root-ball as is.  The two fertilizer treatments will be 1 – 400 grams Osmocote and 2 – control, no fertilization.  The goal is for this to a long-term study – hopefully at least 5-years.  The principal response variables will be survival and growth.  If time and resources allow we will collect water relations data such as water potential and stomatal conductance during the transplant year. 

I was a little surprised that Cambistat did not rate higher.  This product has been heavily marketed to arborists and has been touted to reduced transplant stress.  The active ingredient, paclobutrazol, is a well-known plant growth retardant.  The theory is that it reduces stress by limiting crown expansion and reducing stomatal conductance while roots continue to develop.  I’ve actually been a bit intrigued and may set up a little side study to satisfy my own curiosity.

Thanks to all who took the time to vote.  I look forward to keeping you all posted on the trials! 

Reader input wanted for new book

(Note:  I’ll be doing another blog posting later today.  Just want to be sure I get this out.)

I’m writing a new book on plant physiology for gardeners – a book that explains how plants work and why they sometimes do weird and unexpected things. I’d like to hear what kind of “how” or “why” questions you’d like to see answered in this type of book.  Please add your comments to this post, or send them to me directly. And if there are other gardeners you know who might want to send suggestions, be sure to send them the link!

Smoke ‘em if you’ve got ‘em…

(As an aside, I wrote this before I read Jeff’s Oct. 13 post so don’t read this as a rebuttal!)

 

One of the hallmarks of science is that it pays to keep an open mind.  We all tend to have biases so it’s good to get a reminder once in a while that some things that seem ‘out there’ can actually work and provide some useful information.

 

A case in point.  At the American Society for Horticultural Sciences annual meetings I make a point to wonder through and browse all of the poster presentations – even those that appear to have little relevance to issues I typically deal with.  This year one of the posters that caught my eye was by Orville Baldos and his colleagues at the University of Hawaii and the USDA on the use of liquid smoke flavoring to improve seed germination of piligrass.

 

So first, what’s piligrass and why would you want to improve its seed germination?  Piligrass is a native bunchgrass in Hawaii.  It’s used for conservation and restoration projects and there is increased interested in its use as an ornamental.  It is drought tolerant and fire adapted but production is limited by poor seed germination.  Where does liquid smoke flavoring come in?  Liquid smoke is produced by passing wood smoke through water (I assume someone somewhere has constructed the world’s largest bong to accomplish this).  The water traps a variety of chemical compounds in solution, many of which are useful in giving a delicious smoky flavor to foods that have never been near a grill.  Some of the compounds in liquid smoke are also useful in improving germination of seeds of fire adapted plants, or at least piligrass.

 


In their study Baldos et al. found that germination of piligrass seeds soaked in distilled water was a paltry 0.5%.    In other words, you’d have to sow 200 seeds for each plant you hoped to produce.   Soaking seeds in gibberillic acid (a common method to improve seed germination for a variety of plants) bumped the germination rate up to 20% (5 seeds to get one plant).  But soaking seeds in liquid smoke did better still and doubled the germination to 40%.

 


At the end of the day it’s unlikely that I’ll ever use liquid smoke for anything except adding a little extra zing to my family’s secret barbeque sauce.  But this study is a good example that sometimes things that make you go ‘What the heck?’ can have merit in the end.  Just need to take a scientific approach and keep an open mind.

 

For those interested in the details here’s a link to the poster http://ashs.org/abstracts/sites/default/files/updated_ashs_poster_091911.pdf

Vote early and often!

In my last post I announced that we would be conducting the first landscape transplant experiment designed by social media.  We have about 100 ‘Bloodgood’ plane trees in 25 gallon containers that are leftover from a recent nursery trial.  The trees will be planted at our Hort station and receive minimal care after planting beyond an initial watering and a kiss for luck.  I asked for some suggestions for potential treatments and got some good suggestions.  Unfortunately, one thing I forgot to point out is that I have essentially no budget for this project. So trying to determine whether or not roots are mycorrhizal, or bringing in B&B trees for comparison, are beyond our capabilities at this juncture.

We did have some interest in determining the effects of manipulating rootballs for container-grown trees.  These trees have been in pots for 2 years and I absolutely guarantee they are pot bound.  Definitely a good opportunity to look at shaving or teasing rootballs.

There are a couple of other items that I am curious about.

One is crown reduction thinning.  In forest nurseries trees are often top-pruned to reduce shoot-root ratio and increase transplant success.  Obviously we would’t top landscape sized trees, but can selective pruning to reduce the ratio of crown area to root area reduce water stress and increase survival?

Along these lines, there is a lot of marketing of plant growth retardants to reduce transplanting stress.  The most common is probably paclabutrazole – sold under various trade names including Cambistat http://www.treecaredirect.com/Cambistat-Tree-Growth-Regulator-p/3101.htm  Does it work?

I’ve also been curious about hydrogels.  I’ve long been a skeptic but have had several arborists tell me they’ve used them successfully – of course they didn’t leave an untreated control.

Then, of course, there’s Bioplex.  http://www.bio-plex.com/pdfs/Bio-Plex2009Catalogue.pdf It might be easier to list what isn’t in Bioplex than what it contains. I suspect whatever effect it has is largely related to small amount of nutrients it contains.

Lastly, I still adhere to the notion that fertilizing trees at planting is not necessarily the source of all evil in the world and may even be a good thing.  Here I get a chance to provide myself wrong and apply a dose of Osmocote in the planting hole.

OK that’s the background – time to vote.  The link below should take you to a Survey Monkey survey.  You can vote for more than one item, but please vote for no more than three.

http://www.surveymonkey.com/s/W3YGGSD

 

A Challenge

As I was looking over the label on a bag of fertilizer this morning I was reminded of the time, a few years ago, when a friend of mine and I went to a local K-mart and decided to see what the people in the gardening section knew.  We started small—we went over to a bag of fertilizer and my friend asked what the three numbers on the bag meant.  Now, as most gardeners know, those numbers indicate the amount of nitrogen, phosphorus and potassium in the fertilizer.  Unfortunately the guy we asked told us that those numbers were actually a computer code…We never did find out exactly what this computer code was for.  I have no idea why the guy couldn’t just say “I don’t know”.  We had intended to ask more questions, but both of us were too stupefied to continue.

So I have a challenge for all of you this weekend—I’m curious to see who takes it up—go to a box store, or a garden center—your choice—and ask them what the three numbers on the bag of fertilizer are for.  You can list responses in the comments section below—or feel free to e-mail me directly at gillm003@umn.edu if the answers are too embarrassing!

Be a Part of History!

Here at the Garden Professors we pride ourselves on being on the cutting edge of technology.  In fact, we’re so tech savvy we didn’t even whine when FaceBook foisted a new homepage format on us for no apparent reason.  So it’s only fitting that we offer you, Mr. and Ms. Garden Professor Blog reader, an opportunity to participate in the first ever landscape horticulture research project designed by social media.

 


Here’s the deal.  My current research project on water and nutrient management of trees in container production has left us with over 100 ‘Bloodgood’ London planetrees in 25 gallon containers.  What I need from you are ideas for a study plan on what to do with the trees next.

 

Of course, as with any major research project, the first step in the rigorous scientific process is to come up with catchy acronym for the study.  I propose “the SOcial MEdia DEsigneD TRansplant ExpErimental Study” or SOME-DED-TREES for short.  Needless to say, I am willing to consider alternatives.  In any event, we have a unique opportunity to investigate post-transplanting growth, development and physiology of landscape trees.

 

So here’s what we have: Approximately one hundred,  2” caliper trees, grown in containers in a standard mix of 80% pine bark and 20% peat moss.  Trees have been grown for two years in essentially standard nursery culture – daily irrigation and 60 grams of Nitrogen per container.  The subject of the original study was fertilizer source; half the trees were fertilized with Osmocote and half received the same amount of nutrients from organic fertilizers. After two years we have not seen any difference in growth or foliar nutrients between the treatments. Nevertheless, I will need to include the prior treatment as a blocking variable to eliminate any potential confounding effects.  Beyond that it’s wide open.  We could have 6 treatments x 2 blocks x 8 trees = 96 trees.  I strongly suspect in the final analysis the block effect will be non-significant and we can consider there to be 16 replicates, but life is full of surprises.

 

So, what tree establishment or tree care question is burning a hole in your brain?  “Shaving” or “butterflying” container rootballs?  Fertilizing at time of transplant?  The latest biostimulant?  Crown thinning at time of transplant?  Frequency of post-planting irrigation?  Width of the planting hole – how wide is wide enough?  Send me your suggestions and we will set up a poll to vote for the top choices.

Beer and 1984

1984.  That’s the year that the last professor here at the University of Minnesota published a paper about peanuts.  He had tested a number of different varieties, some of which we’re testing now, and found that they do quite well in Minnesota.  Then for the next 26 years there was a lull.  And now?  We have peanuts!  Boiled peanuts and man are they good.  But…will we end up in 1984 again?  How do we make sure that our peanuts don’t disappear into academic oblivion?  We’ve got to find a restaurant, a bar, a gas station, something, who wants to try something new – we need demand.  Maybe the state fair?  We’ll see.

I give a lot of talks throughout the US.  It’s something that I enjoy, but, honestly, a year or two after I give a talk in a location I usually forget many of the specifics – they bleed together.  Sure, I remember that I gave a talk in Green Bay (for example) – and I remember the people and the botanical garden (both of which were great) – but I don’t really remember the talk itself.  Well, this past Tuesday night I gave a talk that I’ll remember forever.  There’s a bar in Minneapolis called Bryant Lake Bowl which is connected to a bowling alley and a theatre.  Our University Museum, called the Bell Museum, hosts a monthly scientific talk there called Café Scientifique.  The audience, about 90, is waited on by the bar staff during the talk and so everyone is quite comfortable.  The speaker may also partake if he or she so desires (how could I resist – after all, it was the only compensation I received).  So I had a pint of Surly – on an empty stomach – during the talk!  I’m a lightweight, so let’s just say I was relaxed.  It was about an hour presentation followed by almost an hour of questions.  I don’t think it was my best talk ever, but I don’t know that I’ve ever had a better time giving a talk (The title, by the way, was The Truth About Organics).  It was an audience largely composed of a demographic I rarely get to talk to out side of my classes – young (20-30 yr old) people who were very curious about where food comes from and who really hadn’t spent much time thinking about it before.

 

Fall color time…

Did you ever know one of those annoying people who always talks about how great everything is back wherever they were from; the kind of folks that make you want to say, “If things were so much better there, why are you here?”  I have to confess I’m one of those people.  No one’s ever actually given me the “If things were so much better there” line, but I’m sure my Michigan friends have been tempted.  I’m warming to things Michigan but I suspect in my heart of hearts I’ll always consider myself a Washingtonian.

 

That said, there are some ways that Michigan has Washington beat.  We have long, lovely sandy beaches where the water gets warm enough to swim in; which for me means at least 75 deg. F.  Washington has great beaches, of course, but you’ll never see anyone over the age of 12 in the water without a wetsuit – even in August.  We have real thunderstorms spring, summer, fall and occasionally even thundersnow in the winter!  Western Washington is lucky to have two or three bouts of muffled thunder each year.  And we have real fall color thanks to red maples, sugar maples, oaks, sassafras, tulip poplars and others.  Conifers dominate the Northwest and what few large hardwoods there are (big leaf maple, red alder, black cottonwood) drop their leaves inconspicuously without much fanfare.  Vine maples try to make up the difference but usually just add a splash of color here and there.

 

As with many states with rich fall color, “leaf peeping” or “leaf looking” is a popular fall pastime and many people plan fall getaways to northern Michigan to enjoy the color show.  For someone in a position like mine, that means calls from media, AAA, and others asking for predictions on whether we’ll have good fall color.  Of course it’s difficult to predict since conditions during fall itself (i.e., sunny days and cool nights) are among the biggest determinants.  We do know that drought conditions late in the summer can result in early leaf drop or limit production of some secondary pigments, resulting in a shorter and more muted display.  For us in Michigan that suggests a below average fall color show up North since many counties have received 50% or less of their normal rainfall since July.

 

For those interested in learning more about fall color, I high recommend ‘The Fall Color Guy’ website http://biology.appstate.edu/fall-colors The site is maintained by Dr. Howie Neufeld, Professor of Plant Physiology at Appalachian State University.  Howie and I crossed paths at the University of Georgia when he was a visiting scientist and I was a Ph.D. student.  He provides some of the best information I’ve seen on the science of leaf color and his essays on the website are good reads.

My Thoughts on 2,4 D

 

My sister, who lives in the Pittsburgh area, just gave me a call.  She and her husband have two kids and a lawn and she wanted to know my feelings about using herbicides to keep the grass free of weeds.  When we were growing up our parents had a large lawn (and lots of fruit trees) and it took two of us two hours to mow the whole thing.  It kind of turned her off to grass.  The truth of the matter is that she doesn’t even want the lawn she currently has, but her husband wants it – and he wants it weed free.  So she called me giving me the “you’re supposed to know about this stuff” line and asked me what she should do.  My response was that the herbicide her husband would be applying (trimec) wasn’t on my list of super bad things to apply, but that, in my opinion too many people want their lawn too free of weeds.   I don’t see anything wrong with applying an herbicide once a year – it won’t keep a lawn pristine, but it will knock out most of what most people want knocked out.  Why do people insist on having spotless yards – applying herbicides from three to six times per lawn per year?  It’s insane.  Not so much for the safety of humans, but for the good of the lawn ecosystem.  It’s good to have a mix of different plants – it’s healthy.  Using an herbicide really cuts down on you biodiversity, and can affect the safety of dogs too.  You see, 2,4 D, probably the most used pesticide on lawns in the US (and a component of trimec), isn’t rapidly excreted by dogs.  If we are exposed to 2,4 D we just pee it out – our kidneys process it rapidly and out it goes.  In a dog’s system this chemical sits and sits.  It is for this reason that 2,4 D is considered particularly bad for dogs and is suspected of potentially causing cancer.

One more note about dogs.  The reason that lawns get dog spots is because of the amount of nitrogen in the dogs urine – it kills plants – it IS NOT because of the pH of the urine.