woody – Page 8 – The Garden Professors™

An Early Valentine’s Story

In honor of Valentine’s day I have a story about love and betrayal to share….OK, maybe not….perhaps something more along the lines of branches and ants. Same difference right?

There was once a tree that was much loved. It was planted in a cute little corner of a street next to a historic building and was well cared for by its owners. Its many limbs rose to the sky in a seething mass which made the tree look vigorous and robust…and those who planted the tree were very happy.

Over time, however, the people who planted the tree neglected it. The street where it was originally planted changed from a bustling center for traffic to a lonely, out-of-the-way road. As it was ignored its branches grew together and made a mess — and nobody noticed this mess — except for a little horticulturist who had to walk by the tree every day on his way into work.

The little horticulturist was fascinated by the tree. Not because the tree was a particularly fine specimen, no, that wasn’t it at all. Instead the little horticulturist was fascinated by the tree because its limbs grew together so closely that they actually appeared to be grafting with one another, something that the little horticulturist would often spend hours contemplating (what can the little horticulturist say — sometimes he liked to avoid real work).

Two limbs apparently grafted together!

Then one day something terrible happened. An evil green insect invaded the street where the tree lived, and all of the ash trees on that street had to be cut down. Even though the tree couldn’t be infested by the insect (it was a hackberry), it was still on the list. The little horticulturist pleaded with the groundskeepers to keep the tree, but orders were orders and the tree had to go.

But unbeknownst to the groundskeepers the little horticulturist knew one of the people cutting down the tree and asked the tree cutter to save him some of the trees limbs where they appeared to be grafted together. And the tree cutter did, and delivered them to the little horticulturist.

But alas! The grafts that the little horticulturist had seen were not truly grafts at all! They were rotted out sections of trunk which had grown around each other! The little horticulturist was crestfallen! How could this be? He left the decaying limbs in his office as he considered what to do next.

Hmmm…There’s no graft after all –what a mess!

Days stretched into weeks and the limbs continued to sit in the little horticulturists office. And then, one day, from the depths of the limbs sprouted new life! Winged carpenter ants flew around the room and into neighboring rooms! Colleagues shouted curses and obscenities! Graduate students were afraid to use the drinking fountain because of the masses of ants which alighted there! The custodians took to wearing dust masks! And, despite incessant pleading by almost everyone, the little horticulturist would not part with the limbs because he wanted to have props whenever he told the story of the day the ants took over the 4th floor.

The moral of this story is that you shouldn’t hold onto things once you figure out that they’re worthless.

Scrambling for Answers

Yesterday a good friend of mine who works for a well respected tree company in town asked me whether I would be willing to talk about tree conservation as it relates to the emerald ash borer. Specifically he wanted me to make people aware of a statement produced by a group called the Coalition for Urban Ash Tree Conservation which you can find here which was produced by a number of well respected industry people and academics. This statement basically says that we shouldn’t cut down all of our ash out of fear of the emerald ash borer but that we should, instead, treat some with various insecticides to conserve our ash.

I don’t have any major disagreement with the article, but it’s important to remember that every situation is different and that, while chemical treaments might be appropriate for one ash, another should hit the chipper. As the emerald ash borer moves across the country we’ve got to assess what our ash are worth to us and decide when and where it’s appropriate to save them. This is an extremely daunting task without easy answers. The statement by the Coalition for Urban Ash Tree Conservation is good and very appropriate, but what would be even better is a guide to help people decide whether to leave trees alone, to cut them down, or to treat including all of the costs and consequences.

UPDATE: As you might have expected, there is already a cost calculator out there — I just wasn’t aware of it. Fortunately Katie was and left details in the comments section. If you are interested in a calculation to figure out the cost of treating vs. removing ash go here http://www.ag.purdue.edu/entm/Pages/csadof.aspx and then click on EAB cost calculator — it’s on the left hand side. It’s a very nice little tool!

When trees attack!

I’ve been suffering through my post-holiday, post-annual-reporting cold and/or flu, so I don’t feel as witty (or snarky) as I might otherwise be. Instead, I feel like my body’s been invaded by a slowly spreading mass that reminds me…oh, I don’t know…of what trees can do when they encounter an immovable object.

Not much of a segue, I know, but I just had the urge to post some interesting photos after Holly’s photo-fest yesterday. (Memo to self: not fun being Holly’s follow-up act.) Anyway, you’ve seen what happens when growing trees encounter neglected plant tags:

And perhaps you’ve seen how roots laugh at puny planting pits:

So before you feel the urge to attach something – anything – “permanently” to a tree, keep in mind that they have no respect for authority…

…or even those who got them started in life:

Warning: This blog may be hazardous to your health

Following up on Jeff’s post last week regarding blue spruce. Jeff noted, and several posters agreed, that even though blue spruce will eventually have a host of pest problems, for the first 10 years or so it’s a darn good looking landscape conifer. Jeff went on to draw the analogy that choosing a blue spruce is like choosing sexy sports car or gas guzzler over a boring, high MPG sedan. To a certain extent the libertarian in me agrees. If I want to plant a blue spruce in my Michigan backyard or buy a Nissan Titan to commute back and forth to work , by Gawd, that’s nobody’s business but my own. Of course the difference in these situations is that I have EPA reporting to tell me the Titan only gets 12 MPG in the city; for the spruce, people like Jeff, me, and our highly intelligent readers know what we’re getting into from experience and training. But what about the public at large? Maybe what we need are government warning labels for plants. We have them for cigarettes: “Warning: Smoking Causes Lung Cancer, Heart Disease, Emphysema, And May Complicate Pregnancy”, though the European warning, “Smoking kills” is more direct and to the point. We also have warnings for side effects of prescription medications; “may cause nausea, vomiting, headache, hearing loss, oily discharge, an erection lasing four hours, and thoughts of suicide”. Think I’ll take my chances with the disease, thank you.

So what kind of labels do plants need?

Blue spruce: Warning this plant will look great in your yard for 10 years and then fall apart when it becomes a magnet for gall adelgid and loses half its limbs to cyctospora.

Eastern white pine: Caution: This little guy looks like a cute little Christmas right now but in 10 years it can devour your house.

Silver maple: Warning: Don’t blame us when this tree comes crashing though your house during windstorm.

Sweetgum: Caution: Be sure to retain a good attorney for when your neighbors start tripping over gumballs on the sidewalk.

That’s a start. What plants do you think need warning labels?

Will cabling a tree’s crown make it stronger?

In a previous column (December 1, 2010) I discussed the problems that wet, heavy snow can cause for trees and shrubs – particularly evergreens. In response my colleague Terry Ettinger mentioned a cabling technique discussed in the 2^nd edition of Arboriculture (1991). I think it’s worth looking at the science behind this practice and some of the unintended consequences.

Harris’s Arboriculture text is considered the bible for landscape professionals, including certified arborists. In the late 1990’s, Dick Harris was joined by Jim Clark and Nelda Matheny, two other gifted academics who have crossed over into practical writing. In the 4^th edition of this book (published in 2004), the authors caution about routine use of cables and other support systems for tree crowns. They state that “evidence for the use of support systems to strengthen tree structure is anecdotal” and based on my reading of the scant scientific literature on the topic I must agree.

Older articles and texts tend to provide how-to instructions and diagrams on various cabling and bracing techniques, but little to no evidence supporting the practice. More recently, studies have provided evidence that drilling holes for cables, wires, bolts etc. increase the likelihood of introducing disease into otherwise sound wood. As the tree continues to grow and change over time, even the best of these systems may need to be modified or replaced. In fact, the systems should be inspected and maintained annually. Crown cabling is not a permanent, one-time fix – and sometimes it isn’t even a fix. Failures still occur, often just above the point of attachment of bolts and cables. In fact, many arborists believe cabling should be the choice of last resort.

Some current research is exploring noninvasive methods of securing crowns, such as belt systems, that provide support without creating additional problems. As with any new technology, long terms studies are pending. Given the potential risks and lack of reliable benefit, I would not recommend cabling or bracing unless there were no other choices for saving the crown of a tree.

What fir?

OK, it’s the middle of December so I get to indulge my passion for Christmas trees. One of the most interesting projects I’ve gotten to work on during my time at Michigan State is a study to look at alternative species of firs (Abies spp) for Christmas trees and well as for landscape conifers. Firs are fascinating trees that are distributed throughout temperate regions of the northern hemisphere. There are about 50 species, many of which are important for timber, landscaping or Christmas trees.

For those of you that put off your Christmas tree shopping until the end (or want to start thinking about next year’s tree) here are three trees to keep an eye out for.

Korean fir Abies koreana We have several growers in Michigan that are now growing Korean fir. It has relatively short needles that have a bottle-brush arrangement on the stem. The color is often described as dark green, but I’d say the needles tend more to a true green or Kelly green with a silvery underside.

Concolor fir also makes a great landscape conifer

Conolor fir Abies concolor I grew up in the Northwest so I always knew this tree as white fir until I moved to the Midwest. In any case, it’s a great tree. Long, soft-blue needles. Depending on the seed source they can be as blue as a blue spruce. The main draw-back here in Michigan is that concolor tend to break bud early, which makes them susceptible to frost damage in the spring. Their citrus-like scent is hard to beat.

Danish growers compete for the best Nordmann fir in the “Fight for the Golden star” at their annual tree fair.

Nordmann fir Abies nordmanniana Denmark is the leading producer of Christmas trees in Europe and Nordmann fir is their principle species. The Danes like Nordmann because of its deep, dark green color and natural form and symmetry. Europeans don’t like their Christmas trees sheared so they rely heavily on genetics and selection to find trees that naturally have good form. We’re starting to see more Nordmann in the US, both here in the Midwest and in the Northwest. Growers complain that the trees are slow-growing to start but I think some US consumers are looking for a more open, natural-looking tree and Nordmann can fill this niche.

Saving your ash

My earlier post regarding plans to replace the monoculture of ash trees at the Gateway Arch Monument in St. Louis, MO with a monoculture of Lindens prompted a question about options for treating ash trees for emerald ash borer. This is a complex topic so I wanted make sure I had time and space to respond completely.

First, the best and most current source of information regarding treatments for EAB is the Multi-state bulletin “Insecticide Options for Protecting Ash Trees from Emerald Ash Borer” which is available as a full-color .pdf on the EmeraldAshBorer.info website. Anyone who lives in or near EAB-affected areas and is considering treating their ash trees should take the time to download and read this bulletin.

Here are some key points to consider if you want to save you ash:

It is possible to protect ash trees from EAB with insecticides. There are several examples in and around the original core infestation area in Detroit where arborists have successfully protected trees since EAB first was identified in 2002. There are two general options; protective cover sprays and systemic applications. For most trees, protective cover applications will require professional application with specialized high-pressure spray equipment. Most systemic application will also need to be applied by professional applicators, except for small trees that can be treated with soil drenches of systemic insecticide. To date, the most effective systemic product is emamectin benzoate, sold under the trade name TREE-äge. In various tests, emamectin has shown the highest level of control among products tested and is also the only product that consistently provides more than one year of control. Imidacloprid is also effective as a systemic but will need to be re-applied annually for the best level of control.

The likelihood of successfully treating an ash tree declines rapidly once trees begin to show noticeable crown-die-back. In certain cases, researchers have been able to save EAB-infested trees showing some crown die-back, but once 50% of the crown is affected the tree is likely a goner.

Once started, treatments will need to continue in perpetuity. To me, this is the biggest factor homeowners need to consider if they’re thinking about treating their ash trees. To the best of our knowledge, EAB is here to stay. EAB populations may begin to decline once most of the ash trees in a region have been wiped out, but trees in woodlots and forests that have been killed will continue to sprout, providing host material to maintain an endemic population of beetles for the foreseeable future. Systemic applications can provide control but the products will need to be re-applied every year (imidacloprid) or every other year (emamectin) to be effective.

Effectively treating trees larger than 4” in diameter will require applications by a certified pesticide applicator and may cost several hundred dollars per tree. Homeowners need to carefully consider the cost of on-going treatments versus removal and replacement.

Mention of trade names does not imply in endorsement. Read and follow label directions when applying pesticides.

Snow falling on cedars…not always a good thing

Seattle had its first snowfall last week – a mere 3-6″ – and the city shut down. (Yes, those of you in the snowier parts of the midwest and east can laugh…but we’ve got hills. That’s the main problem.) It was unusally cold, so the snow that fell was the light, fluffy kind that I remember from our Buffalo years.

Every year someone writes to ask whether they should remove the snow from their trees and shrubs. Here’s what I suggest:

1) If it’s very cold and the snow is dry and light, I advise leaving the snow on. It serves to insulate tissues from freeze damage.

2) If the snow is wet and heavy (i.e. temperatures are not that cold), you should remove as much as possible. The insulation isn’t necessary, and the weight load can permanently damage trees and shrubs.

This damage can’t be easily repaired; the only alternatives are to cut bent trunks and branches out entirely (no stub cuts!), or to tie them up. Not being into plant bondage, I generally cut bent branches away.

Maybe common sense isn’t so common after all

I noted in my Sept. 22, 2009 post on the threat posed to ash trees in the Midwest by the emerald ash borer (EAB), and included photos of the famous grove of 500 ash trees surrounding the Gateway Arch in St. Louis. I was in St. Louis that summer for the ASHS meeting and saw that the National Park Service was planting trees from a variety of species around the monument. I assumed at the time that the Park Service was preparing for the eventual loss of the ashes to EAB. Boy, did I get a wrong number.

Last week my former grad student, Sara Tanis, alerted me to an article from the St. Louis Post-Dispatch. The Post-Dispatch reports that with the destruction of the grove of ash trees looming, the National Park Service has contracted with a Los Angeles-based landscape architecture firm to replace the monoculture of ash trees with, I am not making this up, a monoculture of linden trees. I’ve heard that the definition of insanity is to keep doing the same thing and hoping for a different result. Apparently the landscape architects that are drawing up these plans have never seen what Japanese beetles do linden trees. Oh, that’s right; the L.A.’s are in L.A.

The article is available on-line if you can stomach it. http://www.stltoday.com/news/local/metro/article_1e65095d-96ae-507a-acda-574d9f54a73b.html

On the bright side, since this is a Federal project it will likely move forward at glacial speed and will require public input. Here’s hoping the Park Service gets an earful and common sense will prevail.

Trunk teaser untwisted

Good guesses over the weekend on what caused the twisty looking trunk structure in Friday’s puzzle. Here’s a larger photo:

Nancy and Paul both got this one – it’s two trunks fused together. I have no idea whether the production nursery grew two saplings together on purpose or accidentally, but here’s one reason that this tree might be a problem down the road:

This area is ripe for disease, as water will collect in the crotch. In fact, the area is already discolored and could be diseased already.

One thing I hadn’t noticed when I took the top picture were the price tags on the nearby pots. They say it all – W(hy) O(h) W(hy).

Needless to say, I hope, is that you wouldn’t want to buy this plant.