The Garden Professors™

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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News flash – genes don’t explain everything!

Last week dedicated blog follower Ray E. sent me this link to a story in the Smithsonian magazine. It’s a fascinating look at adaptive responses by frog eggs and apparently is causing quite a stir in the evolutionary biology community. Phenotypic plasticity, which is the ability of an organism to modify its appearance or behavior based on environmental cues, is being hailed as a “revolutionary concept in biology.”

I don’t get it.

Anyone who’s studied plants for any length of time knows about this phenomenon. It’s why plants grow taller in the shade than they do in the sun. It’s why leaves inside a tree’s canopy are larger and thinner than those on the outer layer. In fact, it’s that darn phenotypic plasticity that can make data collection so difficult for those of us who do field research. Minimal differences in wind, water, soil chemistry, etc. in a research plot (or a garden, for that matter) are magnified once plants start responding to them.

This leads to one of my pet peeves about the state of biological research over the last few decades. If you look at the research that gets the big grant dollars, it’s either at the smallest scale (like molecular genetics) or the largest (like systems ecology). Those of us who are fascinated with how organisms work are pretty much left to our own devices to fund research. (The exceptions to this rules to a certain extent are human and veterinary medicine.)

While this may seem abstract to most of you, the funding imbalance filters down into the teaching function of colleges and universities. When I was doing my undergraduate and graduate degrees, my university had a bryologist (someone who studies mosses), an algologist (marine and freshwater algae), a botanist who specialized in diatoms, and so on. Most major universities had a reasonable number of faculty with expertise over distinct groups of organisms.

As these faculty retired, they were replaced by new faculty whose value was measured more by potential grant dollars than by replacing the loss of expertise. Thus, we have fewer entomologists or mycologists or even horticulturists, as universities scramble for the federal dollars (and substantial overhead) needed to support their institutions and obtainable by a small and select group of researchers. And university curricula reflect this shift, with the disappearance of distinct programs in botany and horticulture and plant pathology and weed science and crop science, as they are mishmashed into bland and unappealing “plant science” departments. Or worse, simply “biological sciences.”

So it’s no great surprise, I guess, that many evolutionary biologists are amazed at the “revolutionary concept” of phenotypic plasticity. I’m not sure many students – or their professors – spend as much time looking at and learning from organisms as they used to.

Over-Interpreting

One of the things that scientists need to be able to do is to figure out what the research that they conduct means without over-interpreting it. This isn’t as easy as it seems, for example, if a particular pesticide at a particular dose kills mice, then should it also kill humans? Without testing we really don’t know – though we certainly have suspicions. If we allow our suspicions to take over and we say that, based on the mouse data, the pesticide necessarily does or doesn’t affect humans then we’re over-interpreting. Most (dare I say all?) scientists have been guilty of over-interpreting their results – or the results of others — at one time or another in their careers. It’s a hazard that comes with the job. Unfortunately it’s a hazard that comes with journalists jobs too — often over-interpreting what scientists say. Recently I had the opportunity to see an online lecture (a TED lecture) on this very topic and thought it was worth sharing.

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.

Final Exam of 2012?

Actually, just a pop quiz.

Continuing the "flowers that look like Christmas ornaments" bit as started on our Facebook page…here’s another, as seen a couple of days ago in our visit to the conservatory at the Biltmore Estate, Ashevegas, N.C.

You can probably guess the family by the leaf shape.

Nice dangly peduncle, no?

Let’s have some guesses, temperate-zone readers! This had me stumped, and I’m not unfamiliar with tropicals. And yes, I want one.

(Zone 9-10 west-coasters: please sit on your hands for a bit, then you can tell us how common it is and "I pull this weedy thing out of my garden by the handful." Ha!!!)

An Interesting Video

Every once in a while someone sends us a news story or a video to look at critically. A couple of days ago Michael got in contact with us through Facebook and asked us to take a look at a video he saw recently and let him know what we thought of it. This video was posted on Russ Bianchi’s website (he goes by the name Uncle Russ). He includes a short note with the video which says “ALL Genetically Modified Organisms, Ingredients, Crops, Livestock, Food, Drugs, Cosmetics, Beverages, Packaging, Flavors, Fragrances, Colors! Soaps and Detergents are UNSFAE AT0ANY EXPSURE LEVEL and are proven to cause cancers, disease and premature DEATH”. Wow. All that from a video? Must be a heck of a video.

Here’s the video.

As far as I can tell, The party responsible for this video is Media Roots which is defined as “a citizen journalism project that reports the news from outside of party lines while providing a collaborative forum for conscious citizens, artists and activists to unite.” Too bad they didn’t include scientists who know something about genetically modified crops. According to Youtube this video has been viewed over 250,000 times.

I can’t tell you exactly what the other garden professors think of it (it may not be printable), but from my end, much of this video is absolute hogwash.

But, having said that much of this video is hogwash, I must give credit where credit is due. The first part of the film which explains how genes are moved from one organism to another was, in my opinion, pretty well done. Sure, there were parts of it that a serious molecular biologist would complain about, but for the average person I thought it was a nice explanation. In fact, after seeing this first part of the film I was expecting to see some really serious and thoughtful critiques of genetically modified organisms – because there absolutely are some good critiques of genetically modified organisms out there. Unfortunately I was sorely disappointed. Let me go through the major problems that this video raised one by one and explain why they’re faulty arguments (I won’t go through all the problems, just the major ones):

Genetically Modified crops show lower yields – Yes, this is sometimes true, genetically modified crops aren’t genetically modified to produce more, just to resist certain pests that might reduce yields (or resist certain herbicides that help control pests). So the maximum yield for genetically modified and non-modified crops are usually pretty similar if the farmer growing the non-genetically modified crop controls pests with pesticides, or doesn’t see the pest for some reason.
Genetically Modified crops have poisons in them – Yes, this is sometimes true. Genetically modified crops may have genes from Bacillus thuringiensis in them (In the video this name was misspelled and the species was capitalized – which is a big deal to a scientist). What the video didn’t mention is that this is an organic pesticide that has been used for years with, as far as we can tell, no adverse effects to humans. The report about people being hurt in the Philippines is a complete red herring. This supposedly occurred in 2003 and all of the data that we have points to a problem besides GMO corn pollen – in fact, the data points to a flu outbreak. This conclusion is strengthened by the fact that GMO corn pollen hasn’t been implicated in a similar incident since then.
Genetically Modified Insulin is bad! – This one does have a grain of truth. GMO insulin is cheap and available, which is why it is used. In the vast majority of patients there appears to be no difference between it and naturally acquired insulin. But it does seem as though some people do have a negative reaction. It terms of deaths, I can’t find much that is trustworthy to corroborate what was said on the video.

I have been chastised previously for being pro-pesticide, pro-GMO, pro-Monsanto, etc. I don’t blame people for saying this because, let’s face it, I do end up defending these things sometimes because their opponents often use bad science. But saying that I’m for these things is going a little far. There is good science and information out there that calls into question the value of certain pesticides, GMOs, and even Monsanto. Look up the new genetically modified Kentucky bluegrass that may be coming out soon. Look up atrazine. Look up how Monsanto protects its patents. These are things I’m opposed to. Another thing I’m opposed to is saying that something is bad without having a good understanding of it. If you’re going to make a video that 250,000 people watch then do your homework and get as much of it right as you can.

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:

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!”

Planting Edibles in Cities

The snow has just started falling and I’m already thinking about what I’m going to be planting next spring. Most of my plantings won’t be at my own house, they’ll be out in the cities of St. Paul and Minneapolis. We’ll be looking at all kinds of fun stuff like growing trees in various new types of containers, adding compost to planting holes in different circumstances, and even pruning methods. But one of the big things that we’re starting to look at are new trees for the urban environment. Cities have always spent time considering what they plant, but with the emerald ash borer ravaging the Midwest, now they’re thinking even harder. And because of the local food movement, suddenly the cities are at least considering trees like apples and hazelnuts on a trial basis (sure, there are some places that use them here and there, but they’re less than common). Of course, if this movement stalls, the cities would be upset at having so many “messy” plants around (that’s their big concern about edibles right now), but I don’t think it will. I’m actually pretty optimistic about using fruits and nuts on public property. Sure, some plants will fail because they get too many diseases or insects, or because they’re weak wooded, but some will make it too. I think hazelnut has a great chance in the right place (it would be too bushy for most boulevards….). Do any of you have a favorite edible that you think might work well in a city? Let me know, maybe we’ll try it!

Closing the loop

Just a short post today as I am participating in an Extension planning meeting for most of the day. One up-side to the meeting is we are meeting and having lunch at Brody Dining hall here at MSU. If you’re around my age and attended college in the 80’s, the thought of eating at a dormitory dining hall might elicit memories of a hair-netted cafeteria lady glopping amorphous slop on your tray next to the mystery meat of the day. Boy, how times have changed. Today, the quality of dining hall food is point of competition for universities angling for students. The Brody dining center is set up like a food court, daily choices for students include a fresh salad bar, southwest food, sushi, made to order pizza, home-style comfort food, even kosher food.

The dining halls are also part of MSU’s sustainability initiative. Food wastes from the dining halls are collected and sent to an anaerobic digester and composted at the MSU Student Organic Farm. The compost is used at the recently completed Bailey hoop-houses on campus to produce salad green and herbs for use in the dining halls, providing a closed-loop system. Is the food produced in the hoop-houses going to make the dining halls completely self-sufficient? Probably not in the foreseeable future. But they do provide a good opportunity to promote horticulture. The project has generated numerous press articles and there are posters around the dining hall highlighting the project. In an age when many bemoan the public’s disconnect between farm and fork, the Bailey GREENhouses remind students, especially those that might not think about it otherwise, where their food comes from.