woody – Page 3 – The Garden Professors™

Silence of the lamb chops

One of my ‘other duties as assigned’ this time of year involves serving as The Christmas tree Guy and responding to various media inquiries about Christmas trees. Last week I posted a link to a media story about Christmas trees on the Garden Professor Facebook page. That post drew a response from Kyle Fletcher Baker who derided cut Christmas trees as “murder of the innocent.” My initial reaction was, “Jeez, Kyle we’re talking about fir trees here not lamb chops or veal.” But Kyle’s post serves as a reminder that there are many people that object to cutting trees for Christmas decoration – no word on how these folks feel about cut flower arrangements but that’s another story. In some cases this objection stems from the belief that Christmas trees are cut from native stands of trees. In fact, virtually all Christmas trees sold at tree lots are grown on tree farms for that expressed purpose.

There is also a sizable portion of the population that believe artificial trees are more environmentally responsible than using a live tree. My personal opinion is this is a fairly small factor in most people’s tree buying decisions but the question persists and seems to get a lot of media play. The American Christmas Tree Association (a trade group that represents artificial tree retailers NOT tree growers) commissioned a life cycle analysis (LCA), which estimated cradle-to-grave carbon footprints for real and fake trees. The bottom-line of the study is that the impact of both is negligible. The tipping point is how far you drive to get a real tree each year and how long you keep your artificial tree. If you get your real tree close to home or combine getting your real tree with other trips, the carbon footprint of the real tree comes out better.

But if the thought of cutting a real tree is still more than your conscience can bear, there is a third option: a living Christmas tree. Many nurseries and Christmas tree farms offer container-grown or balled-and-burlapped trees that can be planted outdoors after the holidays. There are even companies springing up on the west that specialize in live Christmas tree rentals. These companies bring a tree into your house and then pick it back up after the holiday. Some will offer a certificate that the tree will be planted in a park or national forest after its display.

My favorite on-line conifer resources

Posted by Bert Cregg

I just wrapped up putting together a species profile on grand fir (Abies grandis) for Great Lakes Christmas Tree Journal, which is the professional trade publication of the Michigan Christmas Tree Association. I do a lot of articles and presentations on conifers and while I draw on my personal experience and background as much as possible, invariably I’ll need to consult some references. Here are some resources that may come in handy if you need to develop a presentation or article or just want to know more about conifers.

Silvics of North America
Silvics is a forestry term that refers to the “study of the life history and characteristics of forest trees especially as they occur in stands and with particular reference to environmental influences.” Back in the day, just about every forester worth their salt had a weathered and dog-eared copy of Silvics of North America on the bookshelf. Today it is available on-line. Silvics contains lots of basic information about trees species; where they grow, how fast they grow, common best problems, and their genetics. Silvics also includes range maps from Dr. Elbert Little, which are a handy reference when you need to know whether or not a species in native in particular location.

Gymnosperm database
Chris Earle’s website is a botanical tour de force. It covers all gymnosperms, not just conifers but, of course, conifers make up the biggest portion of the site. The Gymnosperm database includes species descriptions for essentially every conifer in the world. Many species descriptions also include images. Earle discusses taxonomy of conifers, which for many species, is taking more plot twists these days than an episode of ‘Law and Order’. There are often interesting tidbits under enthnobotany for many species. Bottom line, you can look up just about any conifer species you know on the database and learn something you didn’t know.

American Conifer Society Database
The previous two resources deal primarily with conifers in their native environment. The ACS is dedicated to the Horticultural aspects of conifers. The ACS database includes hundreds of species and thousands of cultivars. For Picea abies alone the database includes over 200 cultivars. For each cultivar the site presents information on hardiness zone, growth rate, form, color and other characteristics. Many descriptions also include photos.

Going off half-cocked

The good news about being a landscape extension specialist is you get to comment on a variety of landscape tree problems. The bad news? You get to comment on a variety of landscape tree problems. In an average week I probably get 10-15 tree-related calls or e-mails from homeowners, landscapers, growers, extension educators, lawyers, newspapers, and on and on. Sometimes the problem is routine and obvious like tar spot on maples; “I have these spots that look like tar on my maple leaves…” Sometimes the problem looks routine and turns into something else entirely different like the Imprelis herbicide debacle. With the number if problems I respond to, invariable I sometimes end up shooting from the hip – and miss the mark.

Red maple with sparse canopy (right foreground). Maple in left-center of picture across the road was planted at the same time.

A few weeks back I noticed some red maples on campus that were struggling as they were starting to leaf out. There were planted about three years ago following a road-widening project. They are located on a tough site between a parking lot and a busy 4-lane road. My immediate diagnosis was they were weakened due to the aftereffects of last year’s sever heat and drought. I even included a photo of them in an article I did for our on-line extension news. Then this morning I happened to talk to a friend from our campus landscape services. “Boy, those maples sure took a beating from the drought last year”, I volunteered. My Landscape services friend replied, “Well, that and we hit them with Shortstop last year…” Uh oh, now the conversation was going in a different direction. Shortstop is a plant growth retardant, the active ingredient is paclobutrazol, which inhibits GA synthesis in plants and is being widely used by arborists to reduce the need for tree pruning. In this case it worked a little too well and the trees ended up being stunted.

Leaves of paclobutrazol-treat maple (left); untreated leaves on right.

In my defense, I was partly right. Under normal weather patterns paclobutrazol applied at the labeled rates (as was done here) would have reduced shoot growth and leaf growth but clearly the drought exaggerated the effect. So, another lesson learned (actually re-learned) never assume anything about trees until you talk to the people who actually take care of them.

Random acts of horticultural violence

I’ve been traveling in Europe the past few days working on a project with some colleagues in the Czech Republic. While we typically think of our friends in Europe as being more progressive and cultured than us, it appears there are still a few areas where they have a ways to go – such as banning smoking from restaurants and bars – and in learning about the art and science of Arboriculture. (And before the hate mail from Europe starts pouring in; yes, I realize we can find plenty of scenes like this in the US – just hoped I’d find better on this side of the pond).

I’m not a big Forsythia fan, but really…?

Not sure what the desired outcome is here.

This is a black locust near Prague castle. Black locust, which is native to North America, was introduced to Europe for forestry planting in the 19^th Century. The trees were extremely well adapted and have become invasive in many parts of Europe, out-competing native trees and suppressing the development of understory plants. This particular specimen is one of the oldest in the Czech Republic, which presumably is the reason it has been allowed to linger on. A good example of when a tree’s quality of life has run its course. It truly pained me to look at this tree. And, of course, in the U.S. the tree would probably have been long gone due to liability concerns.

The tree is mostly hollow and was once cabled together. The cables were removed after the tree lost its tops in a storm 20 years ago.

It appears that the tree’s principle function these days is feeding woodpeckers.

OK, in the interest of international diplomacy, something Europeans get right is pollarding. In the U.S. what is passed off as pollarding is usually just topping. But when it’s done right (in this case with horseschestnut) and in the right setting (Prague Royal Gardens) it can create a striking effect.

Spring fever: Conifer style

We finally got a reprieve from our wet, cold weather. Just in time for the annual inspection of the conifer troops at the Harper Collection of Dwarf and Unusual Conifers at MSU’s Hidden Lake Gardens. One of the interesting things about making repeated trips to a conifer collection like this is that different conifers stand out each time. Whether due to lighting, background foliage, your mood, whatever; it seems like there are different stars each time.

Here are some of today’s standouts.

Pinus contorta var. latifolia ‘Chief Joseph’
‘Chief Joseph’ lodgepole pine. Discovered in the wild near Joseph, Oregon where Chief Joseph, leader of the Nez Pierce once lived.

Abies concolor ‘Blue cloak’
‘Blue cloak’ concolor fir (white fir for people living on the West coast). One of the most intense blue forms of color fir – rivals virtually any Colorado blue spruce.

Sciadopitys verticillata ‘Joe Kozy’
‘Joe Kozy’ Japanese umbrella pine. Sciadopitys is one of the most primitive forms of conifers with fossils dating back over 230 million years. This cultivar was selected for its fastigiate growth by Sidney Waxman at the University of Connecticut.

And, of course, they always look great when you put them together. For more info on these and other conifers check out the American Conifer Society Conifer database.

Living with lichens

We often hear that the US needs to boost its investment in science education to keep up with rest of the world. While we often think in terms of physics and chemistry when we think of science, we need to remember biology and ecology fit in the mix, too.

I bring this up because of a call a received a while back from a homeowner. The gentleman was concerned /borderline distraught that he would have to remove a prized maple tree from his front yard because it had “peculiar growths all over the trunk”. I told him it was difficult to diagnose a tree problem sight unseen but if he could send me some images, it might help me out.

The photo did indeed make ‘the problem’ obvious.

The growths were lichens. Lichens do not harm trees but I’m sure an unscrupulous tree service could have easily convinced the homeowner his tree needed come out had he not contacted me first. Lichens are actually two organisms; a fungus and an algae that form a symbiotic relationship and function very much like one organism The algae part of the lichen is photosynthetic, and therefore they are able to produce their own energy and do not take any resources away from the tree. In fact, lichens often grow on non-living substrates such as wood, concrete, tombstones, benches and so on. If a homeowner observes a dead tree or dead branch covered with lichens on it, this is a coincidence; the lichens did not cause the branch or the tree to fail. The tree trunk or branch simply provides a porous surface for the lichen to attach. Lichens are often fairly inconspicuous, but in some moist areas, such as the Pacific Northwest, they may form a mat that completely coats branches.

Fast facts about lichens

Lichens grow in some of the most inhospitable places on earth from deserts to tundras.

Lichens are commonly grayish-green, but may also be yellow or red, depending of the type of algae associated with the fungus.

Lichens are sensitive to air pollution, and researchers are investigating their use as a bio-indicator of air pollutants such as sulfur dioxide and ozone.

Lichens are fascinating organisms, if you are taking a liking to lichens try these websites:
http://www.nmnh.si.edu/botany/projects/lichens/
http://www.ucmp.berkeley.edu/fungi/lichens/lichens.html

Selection and Protection: Preventing the heartbreak of splayage

We’ve had considerable discussion over on the FaceBook site concerning snow damage to columnar arborvitae. This is a common phenomenon resulting in a condition Holly has dubbed ‘splayage’.

The question, of course, is what to do about it? My standard response to addressing most problems related to winter injury is there are two options: selection and protection.

Selection means putting the right plant in the right place. For columnar arbs this means not planting them in areas prone to wet heavy snow. Here in mid-Michigan we get a wet snow about once every other year. Last winter we had a 10” of snow in Nov. 30 that resulted in a lot of tree breakage, including arbs. The problem is the branch structure of columnar cultivars such as ‘Holmstrup’ or ‘DeGroots spire’ cannot bear up to the snow weight. Remember these are cultivars that were specifically selected for their upright branch habit, this is not the natural branch pattern of the species (Thuju occidentalis or Thuja plicta depending on the cultivar). There are, however, some narrow trees that are adapted to sloughing off heavy snow. For example, most forms of Alaska false cypress (Cupressus nootkatensis) will do well under heavy snow loads. Also, weeping white spruce (Picea gluaca ‘Pendula’) is a good narrow conifer for snowy locations.

Alaska falsecypress (right) is adapted to heavy snow. Notice how snow hangs on other conifers on the left.

But what do you do if you already have a row of columnar arbs and you live in an area prone to heavy snow? Protecting trees from bending over by tying up the upper 1/3 is often the only reliable option. Note that the all ties or wrap need to be removed in the spring. Yes, it’s a lot of work. Makes the ‘right tree right place’ thing sound better. Note that you only need to provide enough support to keep the branches together, you don’t need to wrap the entire tree like a mummy.

I want my mummy… Does this work? Probably. Question is do you want to look at it all winter?

What about repairing damage after trees have splayed? Some arborists I’ve talked to about this problem have had success tying up tops after the fact provided the trees are tied before any new growth occurs and the branches are bent, not broken. It is important to remember that this is similar to situation with standing and guying up trees after a windthrow event. Yes, you can stand the tree back up but how are you going to stop it from happening again? In the case of splayage, you’re into a cycle of tying or wrapping every year.

Where did the 10-20-30 rule come from? Is it adequate?

We’ve been having an interesting discussion over on the Urban Forestry group on LinkedIn on the origins and suitability of the 10-20-30 rule for tree diversity in urban forests. For those that aren’t familiar, the 10-20-30 rule is a guideline to reduce the risk of catastrophic tree loss due to pests. The rule suggests an urban tree population should include no more than 10% of any one species, 20% of any one genus, or 30% of any family.

The first published reference to the 10-20-30 rule (often referred to as just the 10% rule) was by late Dr. Frank Santamour, Research Geneticist at the US National Arboretum in his paper Trees for urban planting: Diversity, uniformity, and common sense, which was presented at the 1990 Metropolitan Tree Improvement Alliance (METRIA) conference. While Santamour is commonly credited with the 10% rule he notes in his paper, “I am not sure who first propounded the “10% rule”, nor am I sure that anyone would want to take credit for it, but it is not a bad idea.”

The other question on the LinkedIn discussion is whether the 10-20-30 rule is adequate to ensure genetic diversity in urban and community forests. My personal is opinion is that the rule is inadequate but far preferable than the status quo in most communities. If we consider the current issue with emerald ash borer (EAB) in North America, following the 10-20-30 rule means we would accept the loss of 1/5^th of our urban canopy since both of the commonly planted ash species (Fraxinus pennsylvanica or F. americana) are highly susceptible to EAB. On the other hand, many community tree populations the US currently include 30% or more maples, so 10-20-30 would actually be an improvement.

A limitation to the 10-20-30 guideline that Santamour acknowledges is that the rule does not afford protection against insects with a broad host range such as gypsy moth or Asian long-horned beetle. However, while these pests can, and have, caused widespread damage they do not appear to threaten nearly total annihilation of an entire species or genus ala specialists such as chestnut blight, Dutch elm disease or EAB. Moreover, a wide diversity of species is still a better defense even against generalist pests, unless you happen to get lucky and plant a monoculture of the one tree they won’t destroy.

One of the inherent challenges in the 10-20-30 rule is implementation. What is the tree population in question? Are we talking about a city? A neighborhood? A block? If there are 10 trees on a block do they all need to be different species? Some have proposed corollaries to 10-20-30 such as the “Look around rule” (or “Look around, fool!” if you prefer the Mr. T version). This guide states if you’re getting ready to plant a tree; look around and if you already see that tree, plant something else. The problem with diversity on a very small scale is we can end up with the ‘menagerie effect’ – one of these, one of that, one of those – that often lacks aesthetic appeal. Ultimately this becomes a challenge for urban foresters and designers working together; how do we incorporate diversity guidelines within established design principles.

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Buried alive – the roots version

Bert’s post yesterday inspired me to share one of my own timelines that I followed for 7 years. As many of you know, I am a proponent of bare-rooting container and B&B shrubs and trees. One of the benefits is that you can prune away malformed roots, but another is that you can ensure the roots come into contact with the native soil as soon as possible. It’s interesting to see what happens over time with the more typical “pop and drop” method.

I saw this rhododendron being planted in 2002. If you look closely, you can see that it was originally balled and burlapped – the burlap is up around the multiple trunks. Then the burlapped bag was put inside a contained filled with media. You can see that, too. So a hole was dug that exactly mirrored the plastic container and the whole works was lifted out and plugged in.

Visualize a giant jawbreaker with different colored layers. At the center, we have the roots surrounded by clay. This is encased in burlap and twine. Then there’s a layer of container media. And finally we have the native soil. Rather than making it easy for this rhododendron to get established, we now have several barriers for new roots to overcome.

The primary problem here is all of the different textures of stuff in this planting hole: clay, soilless media, and native soil. Water doesn’t move easily through different soil types (remember Jeff’s demo on drainage?) and if water doesn’t move, neither will the roots. And as you follow this time line, it becomes quite apparent that the roots never established into the native soil. Look in particular at the size of the leaves (they are markedly smaller as time goes on – a great indicator of chronic drought stress). The line in the masonry wall makes it easy to see changes in height – or lack thereof.

Installed in 2002 (year 0)

Early 2004 (Year 2)

Late 2005 (Year 3)

Early 2007 (Year 5)

Note the leaf necrosis from chronic drought stress. Having a ground cover competing for water does not help. And neither does pruning off dead parts of leaves.

Now unfortunately I was not able to make it back again until 2009. And here is what I found:

A different kind of storm chaser

As an Extensional Specialist working on urban and community forestry issues, I am frequently asked to respond to questions about tree damage after storms. One standard bit of advice I give is to be wary of ‘door knockers’ or ‘storm chasers’; individuals that descend like locusts upon storm-ravaged areas with pick-up trucks and chainsaws offering to clean up storm damage. Sometimes these are just honest folks trying make a buck but there are also less scrupulous folks in the mix that are clearly exploiting the misfortune of others. In either event, they usually lack the training, not to mention insurance, to tackle the dangerous chore of removing downed trees around homes, cars, and people.

In trolling the internet the other day for photos for Monday’s post, I ran across a different kind of storm chaser. It seems the internet has gone viral with photos of Brazilian glamour model, Nana Gouvea, who was photographed by her boyfriend in various settings among the devastation of Superstorm Sandy. The photos were posted on (and subsequently removed from) from FaceBook. Needless to say, many people were offended and have taken the model and her boyfriend to task for the photos and a FaceBook site has popped up with Photoshopped images of the comely model amidst other disasters from the killing of Bambi’s mother to Noah’s flood.

Personally, I think the public needs to cut Ms. Gouvea some slack. This intrepid beauty has captured a teachable moment and performed a great public service for extension personnel everywhere. I can see future hazard tree assessments talks and bulletins enlivened with her images. Well, here, let me show some examples.

Note the upturned in roots in the upper left. Poor root anchorage is a common cause of tree failures during storms.

Trees breaking at ground-line (far left) during high winds is often the result of girdling roots.

Trees snapping at mid-stem is often the result of a subtle defect. Note the evidence of frost cracking below this breakpoint.