Category: Uncategorized

I’ve been teaching plant physiology or related courses for a long, long time, and one of the tenets is that woody plants don’t heal.  In contrast to animal tissues, when trees and shrubs are wounded the damaged tissues are permanently destroyed.  Wounds are compartmentalized and covered with wound wood.  Arborists are fond of saying "plants seal, not heal."

That’s all fine and good for woody plant parts, but what about grafts?  Since grafting reconnects cambial and phloem tissues, is this "healing?" And what about nonwoody plants, like annual flowers and vegetables? 

Oddly, this type of information is sadly lacking in physiology textbooks, but it’s a question that I get routinely from gardeners.  And it’s not just an exercise in semantics.  People make some poor choices in treating tree wounds, for example, laboring under the false impression that such wounds should be treated with wound paint or bandages so they can "heal."

(with apologies to Blue Oyster Cult)

‘Tis the season for all things Christmas, including the annual hysterical reports of the dangers of real Christmas trees.  Along with heartwarming reports of Thanksgiving feasts at the local homeless shelter and live remotes of frenzied Black Friday shoppers, footage of Christmas trees going up in flames seems to be a staple of every network affiliate in the country.  In fact, in some cases the intrepid reporter will go to great lengths to insure that the Tannenbaum ignites the obligatory conflagration http://www.youtube.com/watch?v=P9dNS5WPncU

What the talking head doesn’t want to tell you is that a fresh, well-maintained Christmas tree is very difficult to ignite.  Numerous fire agencies and others have documented that a fresh tree that is kept watered will self-extinguish even if exposed to direct flame.  And faulty wiring is even less likely to ignite a fresh tree.  The story changes completely, however, if trees are allowed to dry.  http://www.youtube.com/watch?v=RNjO3wZDVlA

Of course, dry trees drop needles as well. So the key to keeping your Christmas safe (and tidy) is to get a fresh tree and keep it watered.  For many trees this means checking and re-filling the water daily, especially during the first week when the tree is brought in the home.  It’s not a real Christmas without a real tree – make sure it’s a safe one as well.  

So far a mild fall has lingered here in mid-Michigan.  With temps in the mid-50’s I was able make much more headway on my fall clean-up than usual.  Typically we get enough early snows or cold-damp November gales that I don’t get to the last of the leaves and frosted hostas until spring.  Leaves are especially challenging here at Daisy Hill farm.  We have about dozen hardwood trees, mainly oaks and hickories, that drop a sizable load of leaves each fall.  For the leaves that fall in the lawn I follow Jeff’s practice and work them into the grass with the mower.  But that still leaves the leaves in the beds and every other nook and cranny they can find their way into.  Then it’s time to pull out the rake and my Craftsman 7.5 hp chipper/shredder; aka ‘My best friend’ (cue Harry Nilsson singing the ‘Courtship of Eddie’s Father’ theme).  I bought the shedder 8 year’s ago and it’s worked like a champ.  The manufacturer claims a 16:1 volume reduction and I’d say that’s a reasonable estimate.  My usual M.O. is to rake leaves, dead perennials, even small twigs into a series of piles and then work my way around the yard.  The main things to avoid are rocks (of course) and plants with long fibrous stems such as tomatoes, which can wrap around the impeller.  In a bit of serendipity, the original bag that came with unit finally wore to tatters so I ordered a new one from Sears on-line.  The new bag actually goes to a newer model and is almost three times the size of the original.  Having to continually empty the bag had been my biggest complaint about the system, so I’m in leaf shredding heaven now.  Since the oak leaves predominate I use the shredded leaves as mulch, putting down about a 1” layer each fall on tree and shrub beds.  It has a nice, natural appearance.  Plus it’s about 1% nitrogen.  Not a huge number, but a good way to recycle what nature have given us.  And certainly better than burning (or attempting to burn) leaves, which is still the most popular disposal method in rural Michigan.

Back in 2006, when I first started garden writing, I was invited to give a talk in Michigan.  It was really exciting to get this kind of invitation so early in my writing career and I was thrilled to have the opportunity to talk to an audience that wasn’t composed primarily of students or academics. 

Looking back at those talks…well…they weren’t particularly good.  Sure, there was good information, but I wasn’t particularly comfortable giving talks at that stage and so I’m not sure I got my information across nearly as well as I should have. 

After my talks there really wasn’t much to do besides listening to other speakers, and so that’s what I did.  That’s where I got to listen to Jeff Ball, a garden writer and self-proclaimed yardener.  I was amazed at how this guy filled the room with people who wanted to hear him speak and further amazed at how well he spoke.   Being in academia I’m always surprised when someone speaks without visual aids – I had always idolized Michael Dirr, my former advisor and one of the greatest speakers I know, who always played off of his magnificent slides of plants.  I really had never seen anyone give a talk without slides, or overheads, or powerpoint, or a chalkboard, before.  But Jeff Ball did a talk right off the top of his head with nothing else, and he was magnificent.  I remember not agreeing with everything he said (can’t remember what specifically), but more importantly, I remember how the tone of his voice and his wonderful sense of timing and rhythm kept the audience interested and engaged.   After that day there were two speakers who I idolized, Mike Dirr and Jeff Ball. 

Jeff Ball passed away this past week.  It’s always sad when someone who you know and admire passes, but their passing also provides a time for you to think back on the good things which they did.  I didn’t know Jeff well at all.  Indeed, I never saw him speak again after that day.  But his talk was inspirational and led me to really think about how I give a presentation, and for that I can’t thank Jeff enough.

“Stealing an idea from one source is plagiarism; stealing from many sources is research.”  This quote has been attributed to so many people I won’t bother trying to list them here.  But the point is a lot of what we do as professors is spend our time digging into the literature to look for substantiating or conflicting evidence for the ideas were interested in testing.  As a grad student back in the 1980’s, a time-honored tradition was to spend the afternoon at the library combing the stacks for journal articles, loading volume after volume onto a cart and then schlepping off the library copy center.  With the mechanical hum in the background and green glare of the scanner radiating off the walls, we’d wear our toner smudges like a badge of honor as the copy machine counte kept track of our progress.

Today, of course, things have changed dramatically.  The hardcopy CAB abstracts have been replaced by Google Scholar and Web of Science.  For those of us at major universities, hundreds of journals are available at our fingertips through on-line subscriptions through our libraries.  And an electronic interlibrary loan request can usually produce a .pdf of even the most obscure reference with a couple of days.  Unfortunately for those of us working in landscape horticulture some of the hardest to find journals were the ones that we often wanted most.  For example, journals from the American Society for Horticultural Science (ASHS) were only available to members and just recently became open access and indexed through Web of Science and other indexes.  Fortunately the situation is improving for two other sources that contain the type of applied research we are often after.  Arboriculture and Urban Forestry (formerly Journal of Arboriculture) and Journal of Environmental Horticulture are both available on-line (or partly available on-line).  More importantly for GP blog readers, neither requires a subscription or university log-in.  

Arboriculture and Urban Forestry is available at http://auf.isa-arbor.com/ 

Journal of Environmental Horticulture is available at http://www.hriresearch.org/index.cfm?page=Content&categoryID=174

Both journals include a search function to make it easier to find related articles.

Yesterday I happened to see a garden calendar encouraging people to pick up their leaves so that they don’t pollute streams and lakes by encouraging algae to grow.  This was a good idea, I thought, but then I started to wonder whether leaves on the lawn might not be a better idea?  After all, the reason that leaves cause algal growth in water is because of the nutrients they have.  And if they have nutrients couldn’t those be used for fertilizer instead of the regular fertilizers which we use?  What if we raked all of our leaves onto our yards?

There’s no denying that leaves which drop in the fall can make great compost, but how well would they work as a fertilizer? So I did a little bit of preliminary research — reading old papers and such — and here’s what I’ve come up with:

Fallen leaves are very variable in nutrient content.  Some leaves have 1% nitrogen, and some can have almost 3% (these are mostly from leguminous trees).  In terms of phosphorus, fallen leaves tend to have around 0.1%, though once again, it’s very variable.   For the purposes of this post I’m going to stick with nitrogen.

For 1,000 square feet of grass yard it takes about a pound of nitrogen per year to fertilize, even with a low input variety.

In a heavily wooded lot it wouldn’t be odd to have around 100 pounds of leaves fall in a 1,000 square foot area.  At 1% nitrogen, the leaves would provide enough nitrogen for the grass, but that would probably end up being a moot point because the leaves would have a good chance of smothering the grass. 

So what I’m wondering is, if we planted trees which were legumes, and had higher levels of nitrogen, and if we chopped up the leaves so they weren’t as likely to smother the grass (using a lawnmower or whatever) could we provide enough nitrogen per year for a healthy low input lawn?  Personally, I think so.  We would need to keep these leaves off of driveways and sidewalks because this is where they would do their worst in terms of contaminating water, but if they were just in yards — I think it might work.

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. 

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! 

(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!