The Flap Over Burlap

This month’s issue of the Oregon Association of Nursery’s Digger magazine includes the second part of a two-part article on urban foresters’ perspectives on nursery stock.  It was interesting to note that some urban foresters felt they were in a quandary because their specs require removal of burlap from B&B trees, yet many nurseries will void their warranty if burlap is removed from the root ball.

Removing burlap from B&B trees is a practice that is widely recommended, yet there is little, if any, data to support it.  The logic, of course, is that burlap will prevent root egress into the surrounding soil after planting.  But is this really the case?  We conducted a study a couple of years ago using 3” caliper B&B green and white ash trees as part of a trial on the movement of a systemic insecticide (imidacloprid) for treatment for emerald Ash Borer.  Since we were using radioactive carbon-14 as a tracer, safety regulation required us to keep the trees contained.  The trees were dug with a 36” tree spade and placed in burlap-lined wire baskets by a local nursery (Discount Trees. Inc.) using their standard procedures. For the study we placed the root balls in large orchard boxes backfilled with top soil.  We removed all ropes and the top of the burlap.  The trees were used for a study that lasted two growing seasons.  At the end of the second season we conducted whole tree harvests on a sub-sample of the trees.  My vision for the root system harvest was that we would simply chain up the baskets and pop the trees out of the boxes; the burlap would help contain the roots, right?  Wrong.  Separating the root balls from the boxes became a major ordeal that involved a whole lotta shakin’ with the front-end loader.  Once the root balls were finally extracted it was obvious that the burlap provided little resistance to root egress into the surrounding soil.

burlap roots
My former grad student, Grant Jones. “He said it would come out easier than that…”

Mike Kuhns at Utah State University conducted a trial several years ago (J. Arbor. 23:1-7) in which he observed a similar phenomenon.  Mike compared root egress of B&B maples with burlap removed versus a single or double layer of burlap by calculating a RTRATIO which was based on the amount of the total root system weight that was found outside the original root ball.  There was no difference in the RTRATIO between trees with single burlap and trees without burlap at any date during the 2-year study. Double burlap decreased RTRATIO initially but there was no difference by the end of the study.    Annela et al. (Arb. & Urb. For. 34:200-203) compared various growth parameters of baldcypress, plane tree, and freemani maples transplanted bare-root or B&B with only the top of the burlap removed.  After two years the only statistically significant difference was an increase in shoot growth for the B&B maples.

So what does it all mean?  My personal opinion is that when it comes to establishing trees in the landscape we spend way too much time worrying about trivial matters like this.  (Digging a planting hole 3X the width of the root ball and amending backfill are others but we’ll save those for another post).   Matching species to site, quality planting stock, and proper after transplant care – especially mulching and irrigation – are way more important but still neglected.  If we plant quality plants in the right place and take care of them properly the first two years after planting we would eliminate 80%+ of the transplant issues I see.  Burlap or no is a tempest in teapot.

Chad and Jeff’s Excellent Nursery Adventure

About 3 months after I started my job in Minnesota I hired a technician to help me run the nursery and to manage research plots.  His name is Chad and he stands about 6 foot 4, has shoulders that threaten to pop the sides of the skid steer loader whenever he enters it, and he knows his stuff because he needs to (and even if he didn’t know his stuff you’d be scared to tell him that because he looks dangerous with his frightening Fu-Manchu moustache).  Currently Chad is responsible for day to day operations in the nursery as well as writing publications.  In other words he’s indispensible.  When you read a post from me, particularly when it’s regarding nursery or landscape research, you’re usually reading a combination of both of our thoughts.  

Over the years Chad and I have seen a lot of nursery stock; some of it good, and some of it bad.  Between us we’ve seen poor pruning, unhealthy root systems, pot-bound plants, trees planted in soil that was much too alkaline or acidic for them, trees planted in the wrong zone, trees sold that weren’t close to the size that they were supposed to be, trees that were girdled by critters, root systems completely eaten by voles and even a tree shot with a handgun.  I once saw a whole field of Japanese maples topped (basically topping is when you cut horizontally through a trees canopy to give it a flattop – talk about competing leaders and narrow crotch angles!).  Seeing that field almost made me cry – A planting worth $20,000 – $30,000 wholesale almost instantly became worth the price of kindling.  But we agree that none of that can hold a candle to Sara’s Nursery (Named after the owner’s daughter).

I received a call a few years ago from a nursery in western Wisconsin (which, for those of you who aren’t familiar with this part of the world, is much closer to the Twin Cities than to Madison, WI where the University of Wisconsin is).  The caller was very concerned that the plants in the nursery which she had been hired to run were failing.  Basically, their leaves were dropping and she couldn’t figure out why.  This was even happening to plants that we usually consider “indestructible” like potentilla.  I had never heard of such a thing, but it sounded like a soil problem and so I asked her to have some soil tests done and to send me the results.  She agreed, but she was distraught and asked me to come and take a look at her operation.  I balked at first, but after a few minutes of begging I gave in.  I asked Chad if he’d like to join me on a trip to the nursery the next day; he agreed and we were off.

The nursery that we found was a retail operation on a road which was once a major thoroughfare, but had been reduced to a minor highway when the interstate, which ran parallel, had been expanded.  Still, it seemed like a pretty good location for a retail nursery in terms of customer traffic.   After we parked the car Chad hopped out and began inspecting balled and burlapped evergreens while I joined the manager to look at their container stock.  It was a mess.  It was the end of summer when we visited, but the leaf drop made it look as though we were in the late fall.

I popped a potentilla out of a container and could find no roots reaching the containers edge.  Taking a closer look I quickly discovered one major problem.  These were bare root plants planted into containers filled with soil.  Soil is almost never a good thing to put into a container because it’s usually too heavy and prevents air from working its way down to the plant’s roots.  The gentleman who owned the nursery (not the manager – in most cases she just seemed to do what the owner wanted to do) was a farmer who had decided that it made sense to save money by using this soil which grew his field crops so well.   This nursery was buying bare-root plants, popping them into containers filled with field soil, and then selling them at quite a mark-up (by the way, this is considered an unethical practice).

This field soil was obviously a problem, but, while plants usually suffer because of the use of soil in containers, I didn’t think it was likely to cause the carnage that I was seeing.  I asked about their fertilizer and watering practices.  Both of those seemed reasonable and unlikely to cause a major problem.

Meanwhile, Chad came back to report on the evergreens.  Almost all of the evergreens (which showed signs of repeated shearing – good for Christmas trees — not good for the long term health of landscape trees) were missing needles close to the base of the tree and appeared to be suffering somewhat.  I thought it might be a water issue, particularly if city water were being used, and asked where it came from.  The manager told me that all of their water came from a well on site.  In this part of the world we frequently have issues with well water being too alkaline, but it usually doesn’t cause the type of damage that I was seeing here.  I filed water away as a possible, but unlikely cause.

I was pretty stumped, as was Chad.  Obviously we saw problems, but these just didn’t seem sufficient to cause what we were seeing.  The manager offered to show us the potting operation, we followed.  The first thing that struck me about the potting shed was that it seemed old, and yet the timbers themselves hardly showed any rot which is kind of unusual.  We asked when the shed had been built and the manager indicated that she had reason to believe that the shed had been built in the 1940s or 50s.

We entered the shed and noticed a large pile of what we assumed to be soil.  Nothing special.  Then our eyes began to adjust to the dim light and we realized that this was no ordinary pile of soil.  It was mostly white.  We were confused.  The first thought that went through my head was “what is this, cocaine?”  Then I thought, no, it must be perlite.  I looked at Chad.  His eyes were big and round.  I went over to the pile, poked my finger into it, and then touched it to my tongue.

“What the EXPLICATIVE DELETED is this place?” I asked Chad (OK, I may not have used those exact words, but it was something close).  The manager must have overheard.

“Well, it’s a potting shed now, but it was built to store salt for the highway” she responded. “That’s just a pile of leftover salt.  We stack our soil against it when it comes in.”

We tested both the soil from the pots and their irrigation water.  Both were ridiculously high in salt (and, not coincidentally, sodium levels).  In fact, salt levels were high enough in the irrigation water that it would literally burn foliage off of the plants.

Shortly after visiting this nursery Chad became a Buddhist and my beard turned more gray than brown.  I can’t swear that it was this nursery that caused these changes, but I can tell you that I haven’t been the same since.

Building a better tree? Not in the long run!

One of the landscape tree production practices that drives me absolutely nuts is heading back trees in the nursery to create “columnar” specimens.  It’s easy to find examples of these in Washington state nurseries, like the pathetic oak shown below:

 

Aesthetics aside, let’s focus on how the tree responds to heading back.  The removal of the dominant leader encourages lateral branches below to become more upright; from these laterals, a new leader is selected.  This new upright growth habit is highly prized by many landscape architects and urban planners, as such trees fit more neatly into small urban spaces without interfering with vehicle and pedestrian traffic.  Sure, it works great for a few years.

Now let’s look at these trees a decade or two later.  Branches grow in diameter as well as length.  All of these acutely angled branches begin to grow into each other, creating bark inclusions:

 

What effect do bark inclusions have on the trees?  These fused branches are not strongly connected; in fact, they are likely points of branch failure.  As these branches become larger and heavier, they can create hazard situations if they are near people or property.  What’s happening here in Washington, and probably elsewhere, is that arborists must be hired to prune out some of these branches to reduce the risk of failure and injury.

 
This…most definitely will lead to this…eventually

I can’t understand why this practice is perceived as “building a better tree.”  To me, it looks like creating a maintenance and liability problem down the road.

As Bad As It Gets?

Last week I took a look at old, out of print books that are worth finding and reading.  This week I think I’ll take a slightly different track and instead turn my attention to a book that is currently in print, but which shouldn’t be.  In fact, 1001 All-Natural Secrets to a Pest-Free Property by Myles H. Bader can be found in many bookstores, was actually one of the best selling garden books of 2006, and is still selling today.  There are other books that I have problems with (Jerry Baker comes to mind) but when considering the worst of the worst this book is all by itself.

I was first introduced to Dr. Bader (he reportedly has a doctorate in Preventive Care from Loma Linda University) one night when I couldn’t sleep.  He was on one of those “paid programming” shows talking about homemade cures for insects around the house.  Normally these half-hour long advertisements cure my insomnia, but not this time.  As someone who loves to learn about and test homemade remedies I was mesmerized by his recommendations and quickly ordered the book.  Sure, on the show he seemed to “dumb things down” a little, but here was a bonafied professor who might have some really cool stuff for me to look at!  I couldn’t wait.

After I received the book I discovered that Dr. Bader used the English language poorly.  This didn’t turn me off to the book though.  I’m pretty forgiving of bad English.  I know that mine isn’t the best and there are sections in all of my books which still haunt me.  Still, the sheer number of errors in Bader’s book was staggering.  For example, here’s a paragraph from page 3:  “His interests have always been in the field of food and cooking and many of his books are related to helping the chef or cook with cooking and kitchen secrets that may gave been forgotten over the years.  This has lead him to include household hints and other related subjects in his books.”   (yes, the words gave and lead are used in the book exactly as they appear above).  And this is just the first page with a significant amount of writing!

Still, I didn’t buy this book for good editing; I bought it for cool, “all-natural” cures.  And so I turned the pages hoping to find something useful.  On page 23 I discovered that the insecticide “Sevin” is organic and is composed of pyrethrums and diatomaceous earth (This is completely wrong, the active ingredient in Sevin is carbaryl, a synthetic insecticide).  I also learned, on the same page, that mixing horse manure with hot water, letting the mixture cool, and then spraying it onto fire ants will kill them (What!?!!?).  There are no instructions about how much of the manure or hot water to use.  Other interesting remedies that you should probably avoid include spraying hairspray onto flies to kill them and using a mixture of 1/3 cow manure, 1/3 sand, and 1/3 clay to coat the trunk and branches of a tree infested by aphids (I’m not sure how this would work since most aphids attack the leaves of trees…). At the end of the book there is a glossary where I learned that Rotenone is a low toxicity poison (never mind that this organic poison was recently voluntarily withdrawn by its makers for use as an insecticide at least in part because of safety/health concerns).  Indeed, almost every organic pesticide was treated lightly, apparently simply because they’re “natural” (which, as some of you may know, is a pet peeve of mine).

The interesting thing about this book is that there were a few useful tips, but with so much hooey it was often tough to tease those tips out.  If you’re one of those people who thinks that a book can be so bad that it’s good then you might enjoy paging through this book, but, other than that, I think this book is best used as a doorstop.

And now I have a challenge for all of you.  Does anyone know of a worse book?  (and, if so, where can I buy a copy?)

Size matters.

Yesterday I received a call from an administrator at a large military base.  (I have to tell you that anytime I get a call from someone in government I immediately start wondering about “the file” that I’m sure is kept on me.  No, I’m not paranoid, but I’m an outside reviewer for a number of graduate student theses from the University of Agriculture in Faisalabad, Pakistan.  In fact, I’m doing two right now.  So every once in a while I am sent a brown paper package from Pakistan.  They’ve always been opened and resealed by the time I get them.  But I digress.)   Anyway, the administrator from the LMB was concerned about a newly installed landscape on the base.  Requirements for landscapes around military buildings specify that plants must be placed a certain distance from the building itself, and not be tall enough to hide people or large objects.  So my caller was concerned that the winter creeper (Euonymous fortunei) which had been planted would start to do exactly what its name implies.  Furthermore, he had done a little Googling and found reports that this plant can get quite a bit taller than what the LMB specifications require.  However, the landscaper was adamant that this plant would not exceed the height requirements and cited one of Dr. Michael Dirr’s books as evidence.  So what, the caller asked, did I think about this?

Several years ago I wrote a myth column on plant size, which you can read here.  Part of this column immediately sprung to mind:  “The lack of consensus among tree identification guides, taxonomic literature, nursery tags, and real-life landscape specimens underscores the fallacy of assuming a uniform maximum height for any species, variety, or cultivar of any tree or shrub.”  In fact, the best predictor for mature plant size – especially for nonnative species – is performance in your local geographic region.  With this in mind, I called my colleague Dr. Sarah Reichard (an excellent plant taxonomist) at the University of Washington.  She laughed when I explained the situation and said that a local specimen at the Washington Park Arboretum had become such a nuisance that the grounds crew had to whack it into submission.  Not only was it well over 12” tall, but it had crept into the nearby Magnolia and was busy making itself at home.

Don’t have a photo of the Magnolia-eating creeper, but I do have this nice truck-eating ivy.

What about the Dirr book?  It’s an excellent resource, but it doesn’t necessarily take into account how climatic differences can influence plant height.  In contrast, the Western Garden Book (by Sunset magazine), though not an academic resource, does look at local plant performance in its descriptions.  I was also annoyed to find that this introduced species is invading the eastern US and is considered a weed in some states. There are lots of good plant choices out there.  Let’s not aid and abet the invasives.

So my caller was armed with definitive evidence and the landscaper will probably have to absorb the replacement costs.  The lesson:  don’t rely on books alone.  Do some legwork in your area to find out what plants are up to – literally.

Sidewalk-eating Japanese maple – not an invasive, but easily outgrows its “expected” space

The Heartbreak of Plagiotropism…

…Otherwise known as “splayage”. When vegetatively propagating some species of woody plants, care should be taken when selecting where to take a cutting (piece of stem) to root.  Propagation from terminal cuttings (pointy end up) usually results in orthotropism or a vertical growth habit.  Cuttings from extremely lateral branches (those that grow parallel to the ground) can, in a few species, result in a spreading growth habit or plagiotropism.

This is not always undesirable – some species are purposefully propagated this way to maintain the prostrate habit that particular cultivar is known for. I’ve propagated lots of Buddleia over the years and don’t recall having this happen. Jeff, you were “Mr. Buddleia”* back in our days at UGA…please weigh in on this!

Floppulence
Buddleia davidii ‘Santana’, author’s garden.

Said plant was purchased from a little Mom & Pop greenhouse as a 4.5” pot with a 6” tall rooted cutting, and it went into our garden in May. It is now lolling all over its neighbors like a drunken sailor.  What looks like a vertical piece in the back is simply propped up by the Canna. No big deal, just a good teaching moment.

‘Santana’ is a bit slower-growing than most cultivars of Buddleia, yet is in great demand due to the wacky variegated foliage. My guess? This is the result of repeated acts of propagation via lateral branches…cuttings of cuttings of cuttings. Not to mention the fact that it’s patented, so this guy may not only be floppy, but illegal (!). One of the purported upsides of the plant patenting process is to control the quantity and quality of propagation through licensing. But that’s another post topic for the future.

*Not to be mistaken for the pageant winner “Miss Buddleia”

Support your local arborist

A couple of weeks ago I was interviewed for the local paper about this year’s fall color.  It’s pretty standard fare around these parts; newspapers, AAA, and so on want to know if we’re going to have good fall color, will it be early, will it last long.  I mentioned to the reporter that we’re seeing a lot of early fall color in the maples around mid-Michigan, in contrast to the northern part of the state, which appears to be running a little late.  The question of course, is why.  I noted even though this summer was relatively cool, trees have been stressed the past several years and some pests, such as clearwing borers, that might not normally be major problems may be taking advantage of the situation.  After the article appeared in the Lansing paper, it was picked up by the Chicago Tribune and USA Today (must’ve been a slow news day).  Since then my volume of “What’s wrong with my tree?”calls and e-mails has skyrocketed.  Depending on how busy I am I usually make an effort try to respond to homeowner calls.  A few issues, such as tar spot on maple, can be diagnosed sight unseen; “My maple has little black blotches on the leaves that look like tar spots”.  Most serious tree problems, however, require a site inspection in order to fully evaluate and diagnose the problem.

If callers and e-mailers really want to get to the bottom of their tree problems I usually tell them to contact a professional, certified arborist in their area.  The International Society of Arboriculture (ISA) provides training and certification for professional arborists.  In order to be certified, arborists must meet certification standards and take continuing training to maintain their certification.  Being an arborist is a tough job.  And the business of being an arborist is made tougher by the low barriers to entry.  Anyone can buy a chainsaw, slap a magnetic sign on the side a pickup, and advertise himself or herself as a tree service.  Quality, professional arborists have to pay for training, insurance, bonding, up to date equipment, and proper safety gear for all employees.  It’s not a very level playing field.  But for the client that is looking to save the oak tree that Grandpa planted when he moved into the house after the war, the knowledge and expertise of a professional is far preferable to the chainsaw of Joe’s Fly-by-night tree service.

To find a professional arborist in your area look in the Yellow pages under Tree Services and look for arborists that are ISA certified and insured.  Also the ISA has a search feature on it’s website that enables homeowners to find an arborist based on their zip code.

Old Books

It’s a rainy day in the upper Midwest.  My favorite time to read.  Of course, I should be writing papers, grading papers, or setting up seminars for next semester.  But instead I’m drawn to my bookshelves.  In most professors offices that I visit the shelves are an odd mix of old and new books that focus on the particular subject which that professor works on, along with the scientific journals that relate to that discipline.  It’s no different in my office, except that I tend towards older books and my tastes are just a little bit more eclectic than most.  I have a particular fondness for old entomology texts and I also like books on garden remedies — whether old or new, academic or not.

In a future post, maybe next week or so, I’m going to go down a rogues gallery of books that I don’t care for, old or new.  But today I’m going to do something a little different, I’m going to tell you the three books that I think are must reads for any gardener or horticulturist.  But the catch is that none of these books are currently in print and so you’ll need to search for them or go to Amazon.com where you can often find dealers who have used copies.  These books aren’t listed in any particular order, except the order in which they came to my mind when I put this post together.

Best Reading Book — The World was my Garden, written by David Fairchild, is one of the best horticultural reads of all time.  I’ve heard Fairchild called the last of the great plant explorers as well as the father of modern plant exploration.  Either title works.  I wouldn’t call him the greatest plant explorer of all time (though it’s no stretch to say that he was one of the best), but he is certainly the most skilled writer (at least in my mind).

Best Informational Book(s) — The Standard Cyclopedia of Horticulture edited by L. H. Bailey is a series of three (or more depending on the edition you get) books which is basically a humongous encyclopedia of everything horticultural.  The beauty of these books is the amount of information they deliver along with the appreciation that the writers (and especially the editor who many consider the father of modern horticulture) had for the art and science of horticulture.  So often we, as professors, want to explain things “scientifically.”  Sometimes gardeners just want to talk about horticulture as an “art”.  This cyclopedia does a great job of appreciating horticulture from both sides.  My favorite section is one called “horticulturists” where an overview of some of the greatest horticulturists of all time is offered, one of the saddest being E. G. Lodeman who died young, but not before writing another of my favorite books of all time, “The Spraying of Plants” — which I won’t include here because it’s a book that will only appeal to a very small audience (those who want to know about pesticides used before1900).

Best Book on Insect Control — Destructive and Useful Insects is a classic text on insect control which has seen many editions dating back to the 1920s.  The best edition, at least in my mind, is the 2nd edition.  The second edition of this book was out before the widespread use of DDT and so, while lead arsenate is recommended a little more than I’d like, there are lots of cultural remedies for controlling insect pests listed also.

I’d love to hear about some of your favorite out-of-print books also — anything from general horticulture to plant pathology and entomology — Let me know what your must-haves are!

Rubber mulch rubs me the wrong way

I’ve been receiving a lot of questions about rubber mulch lately.  For those of you not familiar with the product, it consists of shredded tires that can be dyed and used on ornamental landscapes or under playground equipment.  In fact, the Obamas had this material installed underneath their children’s play structure at the White House.  It seems an ideal way to recycle the 290 million scrap tires we generate annually.

  

But is it?

It’s not effective:  One of the main reasons we use mulch is to suppress weeds.  Research has demonstrated that organic mulches such as wood chips, straw, and fiber mats control weeds better than rubber mulch.

It burns:  You’ve heard stories about piles of scrap tires catching fire and burning for weeks.  Well, those same flammable compounds are in rubber mulch, too.  When compared to other mulch types, rubber mulch is the most difficult to extinguish once ignited.  In fact, some parks and playgrounds no longer use rubber mulch or rubberized surfaces because vandals have figured out that rubber fires cause a LOT of damage.


It breaks down:  Although sales literature would have you believe otherwise, rubber is broken down by microbes like any other organic product.  Specialized bacterial and fungal species can use rubber as their sole food source.  In the degradation process, chemicals in the tires can leach into the surrounding soil or water.

It’s toxic:  Research has shown that rubber leachate from car tires can kill entire aquatic communities of algae, zooplankton, snails, and fish.  While part of this toxicity may be from the heavy metals (like chromium and zinc) found in tires, it’s also from the chemicals used in making tires.  These include 2-mercaptobenzothiazole and polyaromatic hydrocarbons, both known to be hazardous to human and environmental health. 

It’s not fun to be around:  When rubber mulch gets hot, it stinks.  And it can burn your feet.  Yuck.

The EPA’s website says this about scrap tires:  “Illegal tire dumping pollutes ravines, woods, deserts, and empty lots.  For these reasons, most states have passed scrap tire regulations requiring proper management.”   So if we have legal tire dumping (in the form of rubber mulch), does that mean it doesn’t pollute anymore?

(You can read a longer discussion on rubber mulches here.)