January 2013 – The Garden Professors™

What’s a view without trees?

A while back I wrote about a Seattle-area neighbor dispute over a tree partially blocking their view. Sadly, the tree lost out in this case, which was decided a few weeks ago.

Now a second tree vs. view dispute was reported this week. You’ll have to read the story to see how many things are inaccurate/indefensible/infuriating about the “trimming” of this 90 foot western red cedar (a native species). My personal favorite: “the tree violated neighborhood bylaws ensuring no house’s view would be blocked.”

I wonder how they got the tree to agree to the bylaws in the first place?

A western red cedar (Thuja plicata), maybe 60 feet tall. People in my neighborhood like their big trees.

Thomas Knight and the Water Wheel

Classes have begun, and this semester (and every spring semester) I have the opportunity to teach our introduction to horticulture class, otherwise known as Plant Propagation (Hort 1001). We usually have about 120 students, and I don’t want to brag or anything, but it is just about the best class out there. Watching the students learn about seeds, cuttings, and grafting in the labs is one of the most motivating things about my job (and it doesn’t hurt that the greenhouses are about 70 degrees while it’s 0 outside). But, as you might expect, there is a lecture too. Believe it or not, the lecture isn’t half bad. In fact, students actually ask questions in class. This past Tuesday during a lecture on seeds one of the students asked how the roots know how to grow down when they exit the seed. The answer is geotropism. Geotropism is a response by a plant to gravity. Some parts of a plant grow towards a gravitational pull (roots), and some grow away from it (shoots). One of the coolest experiments ever was a study done by a gentleman named Thomas Knight in the very early 1800s where he set up a water wheel which had seeds planted along the edges. As the wheel spun and the plants grew they responded both to the Earth’s gravity and to the force created by the spinning wheel. You can see the results below.

Knight also did some very interesting work showing that buds from older plants retained their physiological age when grafted onto younger plants. Basically that means that if you graft a bud from a mature ‘Honeycrisp’ apple onto a young seedling, that bud will produce a new shoot which produces ‘Honeycrisp’ apples before the rest of the tree produces apples.

Usually when we think of horticulture we think of L. H. Bailey – and we should – but let’s never forget Thomas Knight either.

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?

Gardeners plus QR Codes equals Really Happening?

Proven Winners is putting QR codes on plant tags. So is Walters Gardens, a major wholesaler of perennial liners. Growers often purchase tags from the propagator to go along with the liners. In the case of patented plants, that’s a common method of collecting royalties – the finishing grower has to purchase the tag.

Quick response (QR) codes are everywhere. For those that are vague on the concept, it’s a two-dimensional barcode. Install a code-reader app on your smartphone, snap a photo of the code, and your web browser takes you to a specific site for more information. The marketing experts associated with our industry say they’re a “must” if we want to connect with the ” iEverything” customer. Even botanical gardens are slapping them on plant identification labels, interpretive signage, and more (that’s on my to-do list).

My question: are YOU, dear readers, taking advantage of this technology (as it applies to purchasing plants)? Or is it enough to pull the tag out of the pot and note that this petunia, though oddly-named, needs full sun and gets 8″ to 12″ tall?

Image snagged from Kristy O’Hara’s article “Doing More With the QR Code” in Greenhouse Grower magazine

I realize we have a wide variety of interests and occupations represented – which makes things even more interesting. So whether you’re a grower, a horticulture professional, or a semi-dangerous gardener, please leave a comment as to whether you’ve ever used one. If so, did you find it useful? Any other thoughts?

Almost forgot…Why am I pestering you for this information? I teach the senior level Ornamental Plants Production and Marketing course here at Virginia Tech. If I think it’ll give our future growers and garden center managers/owners an economic edge, I’ll certainly recommend it.

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.

Won’t you help the poinsettias?

Those creative Utah Sate University Extension folks are at it again. Jerry Goodspeed’s hilarious Gnome Management video was a big hit among the gardening crowd a couple of years ago.

His current effort is a bit more…film noir.

"Mission accomplished" if you’ve been shamed into watering that poor poinsettia languishing in the dining room. A little fertilizer wouldn’t hurt, either.

Balance

By this time most of you have probably read all about Mark Lynas, the anti-GMO activist who decided that GMOs are actually a net benefit to society. I’ve been asked by a few people to comment on how I feel about Mr. Lyna’s changing sides. I think they expect me to be jumping up and down for joy. But that’s not how I feel at all. I’m happy when anyone decides to let research lead them to a conclusion rather than politics or gut feelings, but in this case it also makes me nervous. This is because some people tend to travel too far towards one side or another. I’m just as fearful of the damage that people who are radically pro-GMO may cause as I am of radically anti-GMO activists. And, in my opinion, this guy just seems to be radical. Saying that you have research that supports one side of an argument is fine, but in almost all cases there is research that supports the other side too, and you ignore it at your own peril. Balance people — Balance.

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.

</d

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.