Tag: roots

Trees can be good plumbers

A short follow up to last weeks post on girdling roots.  Just to reiterate, the point of the post was that we need to be careful not to jump to conclusions when assessing tree problems.  It’s important to look beyond the first defect we see and consider additional causes.  And to also reiterate, girdling roots can be a serious problem and can lead to tree failures.  The photo below shows an example of tree that was both planted too deep and had stem girdling roots.  The result was a weakened area in the trunk, which was subject to breakage during a windstorm.

Many people also assume that girdling roots restrict flow of water and nutrients in the xylem.  They can, but trees also have the ability graft roots and re-establish connections between roots.  In the study I mentioned last week, Phillip Kurzeja and his co-workers  traced water flow in ’manifold roots’ (a series of interconnected, girdled roots) by injecting dye.  The trees were subsequently felled and de-barked, allowing the researchers to determine whether the roots were still functional.  As shown below the girdled roots were able to re-establish their vasculature and continue to translocate water up the stem. So trees can be efficient at fixing their own pipes!

Image: Phillip Kurzeja

It is important to note that this phenomenon occurs between roots but not between roots and the main trunk – hence the concern for impact of stem-girdling roots, especially for trees planted too deep.

Girdling roots: The source of all evil in the world?

One of the most widely discussed topics in arboriculture and tree care these days is the problem of girdling roots.  Virtually every conference or workshop on tree care has a speaker or speakers on how poor planting technique or poor nursery practices lead to girdling roots and their subsequent correlation with poor tree performance, tree failures, global warming, the soaring Federal budget deficit, and the batting average of the Seattle Mariners.  Before we go any further let me state categorically that I do not think girdling roots are a good thing; nor do I think any of the consequences mentioned are a laughing matter – especially the Mariners’ batting average.  I do think, however, that we often see a rush to judgment as soon as girdling roots are found on trees that are declining or have died.  I attribute at least part of this to the increased availability of air spades for excavating tree roots.  I have nothing against air spades; they are useful tools and a great way to non-destructively examine and treat roots and even move trees.  The problem is that often when people see a tree in decline they examine the roots, see a girdling root, conclude that was the problem and blame the person that planted the tree (unless they were the person that planted the tree, then they blame the nursery).

 

Example of oak tree with leaf scorch (Photo Phillip Kurzeja)

A recent study here at Michigan State presented by Phillip Kurzeja at the recent Arboriculture Society of Michigan ArborCon, points out the importance of looking beyond girdling roots in assessing tree problems.

The problem:  Oak trees at several locations on the MSU campus have been suffering severe leaf scorch.  In some cases virtually 100% of the leaves on the trees are affected and growth has been severely affected.  Examination of the trees by a pathologist ruled out bacterial leaf scorch, suggesting that the problem may be abiotic.  The researchers looked at a battery of variables including degree of leaf scorch, number of girdling roots, planting depth, soil compaction, foliar nutrition, leaf water potential, and leaf photosynthetic function.  Most importantly, they looked at these traits on trees without scorch as well as trees with scorch.

Evaluating girdling roots (Photo Phillip Kurzeja)

The results:  Trees with mild or severe scorch leaf scorch had girdling roots.  At this point one might have leapt to the conclusion that the girdling roots were responsible for the leaf scorch.  But girdling roots were also found in trees that did not have any leaf scorch.  In fact, in some cases the healthy trees had more severe girdling roots than trees with the worst leaf scorch.  So, what factors differed between trees with scorched and un-scorched leaves?  The researchers are still working on the analyses but the most obvious differences were that trees with leaf scorch were consistently planted deeper and had lower levels of foliar manganese than healthy trees.

 

The presentation I saw did not include data on soil pH or soil nutrient levels, so it’s impossible at this point to establish causal relationships among planting depth, foliar manganese, and leaf scorch.  But, for those who have to answer the ‘what’s wrong my tree?’questions, this study does point out the importance of keeping an open mind and looking at a variety of factors and not leaping on the first defect to appear.

Big Trees for Crime Reduction

Like Linda, I believe that we don’t plant enough bare-root trees.  Trees that are harvested and sold bare root tend to establish better and recover faster from transplant shock than trees sold in containers or as B&B (balled and burlapped) stock.  But, in general, trees that are purchased in as bare-root stock are smaller than the other two styles, with B&B generally being the production method which yields the largest trees.

I disagree with Linda that, as a general rule, B&B stock should have its roots washed off prior to transplanting — I’ve done it and I’ve lost trees.  Most of the B&B trees that I know of where root washing has been successful have been small, relatively easily transplanted stock.  Once we have a few nice, big, long term studies that shows that B&B trees with their roots washed perform comparably to, or better than, normal B&B trees I’ll start to believe.  (I will note that, as a rule, it looks like B&B stock is dug and cared for much better here in Minnesota than Washington!)

I’m not going to go into the nuances of the arguments here — we’ve done it before if you want to check the archives.  But what I am going to point out is that a new study in Oregon has shown that bigger trees might help to deter crime.  Yet another reason for the people of this country to demand larger stock.

Despite what all of the research shows (that it’s better to plant smaller trees — preferably bare-root) people want big trees — they want an instant landscape.  They want it because to them it looks nice — and now its a way to protect your family too.

Historically this big stock comes B&B and is very expensive, cumbersome, and not the easiest things to successfully plant.  We need a new, cheaper way to grow large stock.  A number of researchers are working on different methods to produce large stock (special containers, bare root from a gravel bed) but nothing has worked out perfectly yet.  It’s going to be interesting to see how all of this shakes out in the future — especially with the loss of ash trees in the Midwest.

Newsflash: trees will die if their roots can’t establish

I’ve blogged before about the importance of getting tree roots in contact with the landscape soil during transplanting (you can find those posts here, here, here, here, and here). My advice to bareroot woody species upon installation is often ignored in favor of the quick-n-easy methods so often showcased on HGTV (“A complete landscape makeover in a weekend!”). And of course everything looks great…for a while. Let’s see what happens after a few years.

Below are photos of a pine tree, several of which were installed in 2007 at my children’s school (The Bush School in Seattle):

 

Not only is this pine tree planted too deeply (you can’t see the root flare, so it’s too deep), but the twine and burlap were not removed, leaving the roots encased in clay.  Furthermore, we’re not sure how great a root system this tree has since we can’t see it.  Even more horrific, the orange nylon twine is beginning to girdle the trunk.  What’s been planted is a big ball o’ trouble.

I sent these photos and my concerns to the administration and advised them to have the installers (low bid, of course) redo the planting before the one year warranty expired.  My advice was ignored, and here we are three years later:

This particular tree has declined to the point that the foliage is chlorotic and the uppermost needles are dead.  It’s symptomatic of a root system that has failed to establish, which is what I predicted would happen.  But it’s long past the warranty period, so if this tree is replaced the school will have to pay for it…again.  (Though it’s hard to see in this compressed photo, the pine next to this one also has top dieback, and I’ll continue to follow its decline.)

Many professionals, including some of my fellow GPs, disagree with the bare-root approach.  But based on this evidence, how could one argue that bare-rooting would not have been preferable to decline and death?

Dig it up and give it another chance!

Too often I’ve come across relatively young trees, shrubs, and vines that are surviving, but not thriving.  Every year they struggle gamely to put on a few new leaves, grow a few more inches, but something’s fishy and it’s not fertilizer.   Today I’m going to try to convince you to give these languishing woody species a second lease on life.

Long-time readers of this blog will remember some of the root horrors I’ve (literally) uncovered in containerized and balled-and-burlapped plants.  Poor root quality, improperly amended soil, roots swaddled in multiple layers of materials, and root crowns sunk far below grade are some of the most common reasons why roots fail to establish after transplanting.

Fall can be a great time to correct these problems.  For deciduous species, it’s best to wait until the leaves have fallen so that water needs are reduced.  You can find basic instructions on how to install and care for woody plants on my web page.

There are other reasons that plants might not establish, too.  You might remember my long-suffering Clematis, two which had been planted in an area with a perched water table. The lack of oxygen both retarded root growth and created an iron toxicity problem.  I dug them up and transplanted them into containers (during which I had even more fun with overmixing the soil with water and then allowing the undersides of the leaves to sunburn).  They were pretty sorry looking back in July – most of the leaves fell off after being burnt – but here they are just two months later:

And they went on to live another day…

So while you’re out putting your landscape to bed for the winter, take a close look for stragglers.  Give their roots another shot at survival – you’ll be glad you did.

Five little lavenders – an update

Long-time readers of our blog might remember my August 12 column (linked here for your convenience).  You saw my giant lavender plant devolve into 5 small plants with tiny spiraled root systems that put Marge Simpson’s beehive to shame.  In any case, I promised to keep you up-to-date with their progress.

Transplanting in August is a risky proposition, especially when you prune out root defects.  Nevertheless, all but one of the five survived the summer and here they are earlier this spring:

The one that didn’t make it was in the upper left corner of this south-facing landscape, where there is a lot of reflected heat from the nearby bricks and concrete.  (You can see the empty spot where it was in this photo.)

If you haven’t tried corrective root pruning before, I’d encourage you to try it with an inexpensive shrub.  Your best bet will be older containerized plants in the “sale” section of your nursery.

Building a Better Container, Part Deux: The Ellepot

I enjoyed Jeff’s post on the RootTrapper and thought I’d share another interesting and [relatively] new development in the world of greenhouse growing containers.

Take a tube full of growing media, wrap a paper sleeve around it, and voila – the Ellepot!


It’s bottomless, root permeable, and degradable. Each Ellepot sits in its own cell in a re-usable tray.  The great aeration and drainage makes for a happy, healthy root system.  Another plus is that after transplanting, there are no pots or packs to throw away

I’d say the bulk of Elle Pots are utilized at the propagation end of things – starting seeds and rooting vegetative cuttings – either for greenhouses  to “grow on” themselves or as plug/liner products sold to finishing growers (see student Paul Hutcheson holding a geranium liner above).

Ella and Ojvind Ellegard of Denmark developed the system in the early 1990’s.  Popular with growers in Europe, they’ve made their way to North America. Growers can buy in Ellepots by the pallet from various sources, or can invest in the equipment to make them

Wrap it up, I’ll take it…an Ellepot machine at Battlefield Farms, Rapidan, Virginia.

Sizes run from 15 mm (288 cells per 20” x 10” tray) up to 120 mm – equivalent to a  4” pot, perfect for bedding plants. Landscapers love them if they can find them – less waste from installation sites.

Petunia in an Ellepot. That’s Marc Verdel, head grower at Battlefield Farms.

As far as retail goes, I’m not sure if any market research has been done as to consumer preferences for this “pot-less” system. It’s a slight challenge for a shopper to pick one of this and two of that and transport them – you need some kind of carry tray. Anyone out there experienced with Ellepots (grower or gardener)?

Building a Better Container

As most of you know, roots circling around a container isn’t considered a good thing.  And so people try various things to control circling roots.  One of the more creative horticultural minds out there, Carl Whitcomb, a guy why basically got sick of academia and went into private industry (and, as far as I can tell, loathes peer review and the whole process of publication), decided to see what he could do about making containers that don’t encourage circling roots.  He came up with a number of designs, but my favorite is the RootTrapper.  The container is made of a flexible cloth which roots get lodged in, preventing them from circling.  Not that I’ve never seen a circling root in a RootTrapper, it’s just that these circling roots are extremely rare.


A row of elms in RootTrappers


A cut open RootTrapper

This is one of those innovative products that really works and it surprises me that so few people use this growing system.  Yes, it’s a bit more expensive than standard containers, and yes, it does take a little more effort to take the tree out of this container than a smooth sided one.  But man, I’ve never seen a better root system come out of a container than those which you get out of these.

“Being wrong” counterpoint

I haven’t finished with the water droplets story yet – but I just had to add some more evidence to the tree planting discussion from last week.

Consider this series of photos below.  This is a street tree in Kennewick, WA (in the southeastern part of the state, where summers can be intensely hot and dry).  Every spring, this tree leafs out just fine – and every summer the leaves suffer marginal and tip scorch.  This is a classic symptom of chronic drought:

As an amenity, the tree fails.  Even though the landscape is well-watered, as shown by the healthy turf in the next photo, the canopy is sparse and dry.

An excavation of the roots explains why:  the tree was planted too deeply and has developed a secondary set of  roots:

Note how sparse these roots are – which is typical of many adventitious root systems.  While the roots are adequate for water uptake during the cool spring weather, the hot dry summers suck away more water from the leaves than this puny root system can absorb, even when well-watered.

My point:  sure, trees might survive being planted too deeply.  But thrive?  Not in this case – and this is a well-managed landscape!  With less care this tree would have died long ago.  The only solution here would be to replace this tree – correctly.

Let It Snow!

Here in Minnesota one of the things that we need to worry about is the cold.  Over the winter we can see temperatures down into the -30s (even the -40s in the Northern part of the state) and it can damage many of the plants that we grow.  The tops of the trees are usually able to handle these types of temperatures — though a good heavy snowfall can cause a limb to collapse now and again.

The bigger problem is with roots which aren’t able to handle the cold like the top of a plant can.  Once you get 10 degrees or so below freezing you’ve killed the roots of most plants.  Fortunately the ground is a great insulator and doesn’t get nearly as cold as you’d think.  Once you get two or three inches under the surface of the soil temperatures will hover right around freezing for most of the winter.  The plants that are most susceptible to cold are those that are in containers because their roots are above the soil’s surface.  Nursery growers usually protect containers from the cold by consolidating them (pushing them together as in the picture below).

These containers are then covered with a layer of polyethylene fabric, about 6 inches of straw, and then another layer of polyethylene fabric.  Temperatures under the fabric rarely go below 26 degrees or so — even when outside temperatures stay around -20.  Most plants come out fine — our biggest problem is that sometimes voles and mice will take up residence under the tarp and eat the plants — which isn’t a big deal unless its a research project — in those cases we will often use poisons or, more frequently, repellents.

The only thing better than this method is snow.  If we could count on snow every year we wouldn’t bother covering the plants at all.  Snow is the best insulator that we have.  Under snow temperatures rarely go below 29 degrees or so.  So, despite the traffic problems that snow causes, nurserymen and landscapers are always happy to see snow on the ground before the really low temperatures hit.