Bert Cregg

Must we continue to bring in exotics?

A couple weeks back I posted about a collaborative research project that I am involved with to identify seed sources of two Mediterranean fir species (Turkish fir and Trojan fir) for use as Christmas trees in various locations around the country. The post prompted a question from Monta Zengerle who asked, “Must we continue to bring in exotics to satisfy the nursery trade?” Since our intended purpose is Christmas trees and people move plants around the world for purposes other than nursery stock, I’ve broadened the question to “Must we continue to bring in exotics?” for this discussion.

Not all exotic species introductions are man caused. This dock washed ashore in Oregon following the Japanese tsunami carrying all kinds of critters with it.

The answer, of course, is “No.” As human beings the only things we absolutely have to do are eat, sleep, and breathe. But the reality is much of the food and fiber production around the world, as well as our amenity plantings, are based on exotics plants. Human agricultural history is largely the story of plant importation and subsequent breeding. As Thomas Jefferson famously observed, “The greatest service which can be rendered any country is to add a useful plant to its culture.” However, it is doubtful that Jefferson considered kudzu or purple loosetrife could be among those plants added to our culture. Today we have a different understanding and realize that along with the economic benefits of plant exploration and importation comes the possibility of unintended and serious ecological consequences. And we’ve realized this for some time. People that deal with plant introductions on a regular basis talk about ecological errors and economic errors. If we allow importation of a plant that later turns out to be ‘bad actor’, we’ve made an ecologically harmful decision; if we ban a useful plant that ultimately would have turned out to be non-invasive, we’ve suffered an economic loss. Fortunately, only a small percentage of exotic species become naturalized and only small percentage of naturalized species become invasive. The underlying challenge is we cannot predict with 100% certainty which plants will be invasive in a new environment and which won’t. Ecologists are working on it and we can certainly begin to judge the invasive potential of new introductions. In the meantime, we are left with the imperfect calculation of whether the potential economic upside outweighs any potential environmental risk.

‘Top-work’ on noble fir in Oregon to maintain a single terminal leader. Turkish fir typically require less top-work.

So let’s look at our current project as a case study. What’s the upside? Christmas tree growers in the U.S. produce roughly 20 million trees annually. That’s a potential economic impact of hundreds of millions of dollars and seasonal and full-time employment for workers on over 13,000 farms from North Carolina to Washington State. A major issue for growers in virtually all of the principle growing regions is phytophthora root rot. Previous work at Oregon State University indicates that Turkish fir is highly resistant to this pathogen. By identifying seed sources with phytophthora resistance and superior Christmas tree characteristics (tree form, needle color, post-harvest needle retention), we will enable growers to continue or expand production and give consumers an additional choice for their holiday tree.

Native noble fir (left) is highly susceptible to root rot. Turkish fir (right) is much more resistant.

What’s the down side? As I mentioned, predicting invasiveness is difficult. That said, firs have several characteristics that make them unlikely invaders. Most firs have a relatively long juvenility period (age before they produce seed) which means they have a long period between generations. Secondly, most fir species produce seed crops sporadically as opposed to producing heavy seed crops year after year. Ecologically, firs are pretty wim
py; growing best on moisture, well-drained sites and unlikely to aggressively colonize disturbed areas. Lastly, the best predictor of invasiveness is invasiveness – a plant that has become invasive in one location is a candidate to become a repeat offender in a similar environment. Among conifers, the greatest issues with invasives have been pines (genus Pinus), in the southern hemisphere. In fact, all of the documented cases of invasives in the pine family (Pinaceae) are Pinus species; none were Abies. Based on all this, the likelihood of Turkish fir or Trojan fir becoming ecological problems appears very small, while the potential to add a useful plant to our culture is clear.

Exotic giant sequoias at Hoyt arboretum, Portland, OR.

Richardson, D.M. and Rejmánek. 2004. Conifers as invasive aliens: a global survey and predictive framework. Diversity and Distributions 10:321-331.

Rime and Reason

This weekend I got to take a leisurely drive to the northern end of Michigan’s Upper Peninsula with my daughter so she could check out Michigan Tech University. Lots to see along the 488 mile drive from DeWitt to Houghton, including a moose, lots of snowmobiles, and the world famous ‘Yooper tourist trap’. (For the uninitiated, people that live in the U.P. are known as Yooper’s, while those of us that live beneath the Mackinac Bridge are known as ‘Trolls’) Once we got along the Lake Superior side of the U.P. we drove through a short section of freezing fog that produced rime on the surrounding forest. Our tight schedule and road conditions prevented me from stopping to get photos but I found several on Wikimedia commons that illustrate the phenomenon.

Here’s a recent TV weather blog that provides some additional photos and information rime and hoar frost, which is a related winter weather phenomenon. Rime forms when air temperatures are below freezing drop below the dew point as the water condenses and freezes, the ice crystals accumulate on the windward side of trees, fences, and other objects. Another similar phenomenon is hoar frost. Hoar frost looks similar to rime but is lighter and not associated with freezing fog. It forms when surfaces cool below the dew point and ice crystals accumulate. Here are some examples of hoar frost we experienced a couple years ago here at MSU.

You don’t have to be crazy to work here, but it helps

Recently I spent a week in Oregon working on a Christmas tree genetics project along with my colleagues Chal Landgren( Oregon State University), Gary Chastagner ( Washington State University), and John Frampton (North Carolina State University). The objective of the project is to identify superior seed sources of Turkish fir and Trojan fir for use as Christmas trees around the United States. We refer to the project as the Cooperative Fir Genetic Evaluation or CoFirGE – remember, the most critical step in any experiment is coming up with a catchy acronym. CoFirGE began with a trip by my colleagues to Turkey where they collected seed from 100 fir trees across a range of sites in Turkey

Turkish fir growing in western Oregon

Why are we interested in these species? Both Turkish and Trojan fir are closely related Nordmann fir, which is widely used as a Christmas tree in Europe. These species make wonderful Christmas trees due to their symmetry and needle color. In addition they may be resistant to diseases, particularly Phytophthora root rot, that plague Christmas tree growers from Washington State to North Carolina.

So, what was going on in Oregon? After the seed were collected in Turkey they were sent to Kintigh’s nursery near Eugene, Oregon, where the seed were sown to produce seedling plugs. The next step of the project will be to send the seedlings out to cooperators in five locations (Pacific Northwest, Michigan, North Carolina, Pennsylvania, and Connecticut). This is tree improvement on a grand scale. In each region there will be two test plantings and each planting will include 30 reps of 100 seed sources or 3,000 trees. Multiplied by 5 regions and 2 plantations that’s 30,000 trees total that we will collect data on for the next 8-9 years.

30,000 seedlings ready to be sorted and shipped

Each seedling is individually labeled with a bar code for identification

Sorting into to boxes to send to cooperators around the country

But step one is getting the seedlings from the nursery to the out-planting sites. That means lots of tagging, sorting, and bagging. With help from technicians and students from WSU, OSU and NCSU and staff from Kintigh’s we were able to get all the seedlings sorted and bagged by mid-day on Thursday and start them on their journey to their new homes. Next step: Planting…

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

Pussy Riot: How far should we go to eliminate destructive alien species?

A short article in our Sunday paper caught my eye this weekend. New Zealand economist Gareth Morris has launched a campaign to eliminate domestic cats from the country in order to preserve native bird populations. According to Morris and his supporters, cats represent a serious threat to many rare and endangered bird species in New Zealand, which has the highest rate of cat ownership in the world. Ironically, one of the reasons the article our paper caught my eye is I have been considering adopting a feral cat from a local program to control mice in our barn.

So, what do you think? Are cats useful companions and mousers or do you agree with Morris that they are ‘natural born killers’ that need to be eliminated?

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.

How to give a better talk

This past week I gave a talk at our state wide nursery and landscape trade show. After my talk I stuck around and attended a couple of sessions, most of which were pretty good. One talk, however, set my teeth on edge. The presenter was a grounds manager for a local college that has embarked on a program of all-organic landscape care, including use of compost tea. Personally I don’t know much about compost tea aside from the fact that mention of the term causes Linda to go apoplectic. But I try to keep an open mind about such things so I grabbed a seat near the back of the room to see if I could glean a useful nugget or two. After 20 minutes I thought I was going to need to have someone physically restrain me from wrestling the speaking to the ground and pounding the remote from his hand like a smoking gun. He wasn’t a scientist and made no claims of such, nevertheless there is one fundamental concept of the English language that every presenter at a professional meeting like this must never, ever,ever, ever,ever,ever,ever,ever, forget. It is this: Words like better, larger, more, taller, healthier, and so on are comparatives. And any time we use a comparative it is followed by ‘than something’ otherwise it is meaningless. As I noted in one my earliest post on the blog, advertisers use comparatives without actually comparing them to anything all the time. “Scalp and Shoulders shampoo gives your hair more shine.” More shine than what? Not washing it at all? Rinsing with this morning’s leftover coffee? So every time this guy blathered on about how compost tea made the landscape healthier or the organic program made the lawn greener, I was like Alice in the Dilbert cartoon; “Must… control… fist… of… death…” I will freely admit to having biases against potions that sound like something concocted by the Macbeth’s witches, but as discussed in my post on PGR’s I can be persuaded by credible data. In this case there were none forthcoming. While many in the large crowd listened intently and took copious notes, the speaker waxed on about improved organic matter, reduced disease pressure, and improved growth and vigor. His evidence? He had a microscope slide of a drop of compost tea and which showed living bacteria. That was it. Hate to break it to you guy, but most 4^th graders have looked at the same in a drop of pond water. During the question and answer session I finally spoke up. I admitted my biases and skepticism up front and asked straightforwardedly, “Do you have any evidence that the compost tea did anything?” The speaker, who was earnest and likable enough confessed, “No, not really.” I applaud his goal of trying reduce chemical inputs compared to past practices. I respect him for his willingness to give a 2 hour talk in front of 150 people. But without any data or clear point of comparison eventually you become a huckster trying to shill a product.

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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Happy New Year

As trite as it sounds, I try to slow down and enjoy the simple things around the holidays. We are starting to get some more seasonal weather, which means cold temperatures and occasional snow flurries. Once we get our first real snow cover I pull out my birdfeeder from beneath the shop-bench in the garage, fill it up and set it in a beech tree outside our kitchen window. No one in our family is a birder but it’s interesting to see how nearly everyone takes time to linger over their morning coffee or tea to watch the steady parade of chickadees, nuthatches, cardinals, and jays at the feeder. The feeder itself has some sentimental meaning as well. I bought it at an auction for the Arboriculture Society of Michigan meeting several years ago and it was handmade by Dan Kurkowski, longtime city forester for Detroit. Dan was a tireless tree advocate for the Motor city who passed away, much too young, six years ago but I always remember his passion for people and trees. And every time I set out the feeder he built I remember how he closed every e-mail with the line for the Lorax, “I speak for the trees for they have no tongues.”

I hope everyone enjoys a quiet and restful end of their holiday season.

Why oh why? (Buried alive version)

Sometimes when I’m stumped for ideas for blog posts, I get in my car and drive around my neighborhood. Usually within 10 or 15 minutes I’ll see something stupid enough to write about. Today was no exception. We live in a mostly rural area north of East Lansing but development is slowly but surely encroaching around us. Part of that development includes a couple of golf courses. One of the golf courses recently announced they were going to develop a high-end RV park adjacent to their course. If you’re like me, ‘high-end’ and ‘RV park’ don’t sound like they belong together in the same sentence but I’ll take their word for it. In any event, when the project was announced the developers placated local residents by noting they would install a large berm around the RV park to screen it off from two highly traveled roads next to the park. Said berm was installed about a month ago.

Anyone see anything wrong with this picture? There are about a dozen trees in similar straights. Doesn’t give me much faith in the rest of this project…

I think the one on the right will be OK (it’s a telephone pole). The one on the left, not so much…

“Quit yer bitchin’. Ya wanted a berm, we built ya a dawgone berm!”