Bridging research and reality

This summer, I’ll be giving a seminar on “Arboriculture Myths” at the ISA conference in Portland, OR. I’ve been quizzing arborist-types for a few months now to find out what myths they would most like to see debunked during my talk. Intermixed with the suggestions of dubious products and questionable practices there was this question: “How often do the results from research with limited scope get over-extrapolated?”

I like the question a lot, because this is the fine line that we Garden Professors walk in bringing you the newest scientific information we can find.  As a rule, I tend to hold back on recommending anything that has only been tested in a lab situation.  I like to see field test results, where environmental variation will quickly swamp anything with marginal effects.  In other words, if something can make it through an experimental, replicated field test, I can get excited about it.

Which brings me to a recent article in Arboriculture and Urban Forestry (2012, Vol. 38, Issue 1, pp. 18-23. And no, I can’t post it on the web). Briefly, the article describes an experiment where water evaporation was measured in pots filled with various substrates, which were either left uncovered or mulched with about 3” of pine bark.  The results showed little difference between the mulched and unmulched containers.

As the authors point out in the discussion, it’s an artificial system that includes no trees, nor any way for water to move through the soil except from the top down.  And I really don’t have a problem with the methodology, or the data generated, or even most of the discussion. What bothers me is a single sentence at the end of the abstract:

“Given the minor reduction in evaporation, and reported disadvantages of mulch application close to the trunk, landscape managers might consider changing mulch application practices for newly planted trees.”

Wow. How did we get from a series of containers with no plants in them to this recommendation?

Every gardener knows the value of mulching – a perception that’s substantiated by hundreds of publications. Since I’ve written about mulches on the blog a number of times I’m not going to belabor the point. But I will refer readers to a short Ecological Restoration article I published a few years ago that most definitively linked mulch application to plant survival in restoration sites; Bert also published an article on the benefits of mulching and lent me a few photos to illustrate. And Jeff has even more data on the topic, including some that may radically change the perception that mulch against tree trunks is a bad thing.

Mulch increases soil moisture


Which plot would you rather have in your garden?

Those of you who read scientific journals probably read the abstract first – I know I do. If it interests me, I’ll read the entire article. But sometimes the abstract is the only thing you can find online. And for this reason, the peer-review process in many of the journals asks whether the contents of the abstract are justified by the results. Honestly, I don’t think this article meets that standard.

Does anyone really know how to handle weather?

Lots of people around the country seemed to take perverse pleasure in the snow and ice storm that paralyzed much of the Pacific Northwest recently.  From Boulder to Boston, northern residents that deal with snowstorms on a regular basis chortled at video clips of cars and buses slip-sliding away in western Washington.  Perhaps it’s just the Northwesterner in me getting a little defensive, but I’ve never understood why people feel the need to gloat over other people’s inability to cope with weather.  At the end of the day we’re all in the same boat.

I’ve lived in the Northwest, the Plains, the South and the Midwest.  And guess what?  Nobody can handle weather they’re not used to or equipped for.  On NPR the other day I heard a former Chicago resident now living in Seattle bragging how his former city dealt with snow and couldn’t understand why everyone was making such a big deal about a little snow.  I used to live in Georgia and people there were similarly perplexed when a few days of 100 degree heat killed hundreds of people in Chicago.  Likewise, I can remember my amazement shortly after I moved to Michigan and saw a scroll at the bottom of the morning TV news announcing 2-hour school delays for fog.  I’d never heard of such a thing.  If we had fog delays in Olympia, we’d have started half our school days at 10:30.

On the eve of the recent Northwest snowstorm I saw an interview on the Weather Channel with Seattle’s transportation manager, who said they had 30 snow plows standing by.  Custer had better odds.  To put things in perspective it would be like the city of Lansing having 6 plows (it has more than 60).  Seattle and western Washington are not equipped for snow, nor does it make any financial sense for them to do so.  Just like it doesn’t make sense for everyone in the Midwest to have central air or to equip every Michigan school bus with fog lamps.  Just remember, when you get ready to gloat over someone else’s weather misfortune, Mother Nature will always have the last laugh. 

New weekend feature: “what I learned from my garden”

While in Connecticut a few weeks ago I met Henry Young (a former horticulture extension agent), who did a guest post on the blog this past week about the important of “negative” results.  He also had another interesting idea for the blog that I’m going to initiate this weekend – the “What I learned from my garden” feature.

I did one of these back in July of 2010, when I worked water into a clay loam soil the same way you might work it into potting mix – with disastrous results.  So to kick off our new weekend feature, here’s another story from my “oops” collection:

Nearly every place we’ve lived we’ve had a wisteria vine – carefully trained and maintained so it wouldn’t get under the shingles and other places it wasn’t welcome.  In Buffalo, we had a second-story open porch off our bedroom with decorative iron fencework around the edge.  How lovely it would be if we planted a wisteria below and trained it along the fence, so that we’d have purple clusters dripping from the black ironwork in the spring!

We got the vine planted and it quickly reached the second story, twining its way around the fencework.  All we did was keep the wild hairs pruned off and waited eagerly for the floral show.

Well, it never bloomed in the four years we had left in that house.  But it did grow vigorously.  The slender vines thickened into bloated things that grasped and pulled at the fencework, pulling it off-kilter in its eagerness to take over the south side of our house.  The fence and the wisteria were becoming one.

Fortunately, we moved before I had to take an ax to the thing, and to this day I have no idea what the new owners did with that unholy alliance of metal and plant.

We learned – our current wisteria is restricted to a sturdy wooden trellis that laughs at its attempts of herbal domination.  But it still hasn’t bloomed…I assume it’s sulking.

Wisteria on the right, along with indestructible trellils

This feature will succeed if YOU contribute!  Send me your stories, with photos if possible, and I’ll post them on weekends.  We’ll all laugh and learn together.

There are papers out there on almost everything!

It amazes me how much information is out there if you really look for it.  This morning I was having a discussion with a couple of friends about how and why asparagus affects the odor of urine (I might or might not be able to let you know why next week — after my administrators decide how much potty humor they’ll let me get away with).  Anyway, I decided to see what I could actually find out about it and found a remarkable number of papers on the topic including this recent one on odor perception.  In a nutshell it says that there are actually differences in the way we produce and smell that characteristic scent that asparagus gives urine.  The introduction is quite interesting — I even pulled this nugget out “Proust wrote more favorably that asparagus “as in a Shakespeare fairy-story transforms my chamber-pot into a flask of perfume” “.  Hmmmm.  Participants in the study had to smell other peoples urine to grade its odor level.  In fact, here’s another quote from the article:  “Some subjects were unable to complete some parts of the testing. For instance, some people could not complete the smelling phase because of unanticipated aversions to urine.” Interesting.  These people had, presumably, been around urine all their life.  Probably even produced some themselves.  How could they not know they were averse to it till now?

Here’s what I want to know:  Is there a market for asparagus that doesn’t result in the odor, and, if so, is it even possible to breed this trait out or is the flavor of asparagus intimately tied to this mildly unpleasant side-effect?  Now there’s a problem for a breeder!

The new Hardiness map’s here! The new Hardiness map’s here!

I probably shouldn’t admit this but one of my all-time favorite movies is Steve Martin’s classic “The Jerk”.  Part of the appeal is that I have an affinity for low-brow humor in general but also because the movie contains some great lines; “I was born a poor black child”, and the classic scene when Martin’s character finds his name in the phonebook for the first time and runs around yelling, “The new phonebook’s here! The new phonebook’s here!”

I wasn’t quite as excited as Navin R. Johnson today, but pretty darn close.  The reason? The USDA (finally) released a new hardiness zone map for the US.
Why is this exciting news?  Well, for several reasons.  The earlier version of the USDA map was released 1990.  The 22-year-old map had several limitations.  First, it was 22 years old.  Secondly, the versions of the map that were available electronically did not reproduce well and had poor resolution when you tried to zoom in on a particular area.  This sometimes made it difficult to identify the hardiness zone for certain locations and limited the utility of the map for presentations and publications. 

There have been persistent rumors for last 6 or 7 years that the USDA would release a better, updated map.  In addition to the shortcomings of the old map in terms of resolution, many felt the map didn’t accurately reflect more recent climatic conditions.  In 2006 the National Arbor Day Foundation released an updated hardiness map using more current climatic data.  This map indicated that many locations were 1 or even 2 hardiness zones warmer than the 1990 USDA map.  In addition, the Arbor Day map was available as a hi-res TIF file suitable for PowerPoint presentations and had a ‘zone-finder’ feature based on zip codes.

I haven’t had a lot of time to work with the new USDA map, but my initial reaction is a thumb’s up.  Like the Arbor Day map, the new USDA map has a zone finder based on zip code that makes it easy to find the zone in your area. The map is interactive, allowing users to zoom in or out.  As with MapQuest and other on-line maps we’ve grown accustomed to, it allows the user to select a roadmap or satellite background and choose different levels of transparency or opacity.

Whenever I discuss hardiness zones, I always include the caveat that these maps are based on average annual minimum temperatures.  That is, they are based low temperatures we are likely to see in an average year.  Not sure about where you live, but I have yet to see an average year in my adult life.  There are many years when we will get below our USDA hardiness zone temperature.  Human nature says we want what we can’t have and gardeners love to push the boundaries of their hardiness zone – people in zone 4 love to grow zone 5 plants; people in zone 5 love to grow zone 6 and so on.  Just because the new map may say you’re a zone warmer; your climate hasn’t changed, the map is just based on better and more recent data.

A plea for published “negative results”

Last week I was in Connecticut speaking to the Connecticut Tree Protective Assocation.  It was a great chance to meet arborists on the east coast, and especially heartening to meet yet another group of professionals who demand good science-based information to guide their practices.

After this meeting, I had a thoughtful email from one of the attendees regarding the lack of "negative results" publications in the scientific literature.  It’s a message that’s important for academics as well as the gardening public.  Here’s Henry’s email:

"Thank you for the comments and presentations you delivered on Thursday, January 19. I hope you had a pleasant and less difficult return journey from Connecticut.

"One point that you mentioned bears emphasis and enlargement although you got it right the first time. Specifically, you mentioned one anecdote that has additional implications, the researcher friend who was reluctant to publish findings that disappointed her because they did not bear out her original conclusions, i.e., the feeling of disappointment and the chagrin to have missed one’s own best guess. These are natural feelings and you are not the first in my experience to notice this very human inclination in scientific researchers. There is a rush to publish meaningful results, but the negative findings tend to pile up in the stack of unpublished material.

"The root of this matter, it seems, lies in the unwritten assumption that science is the means by which we discern and expose the truth. Certainly that’s what is hoped since it could lead to recognition and prestige.

"In fact, it is just as useful, if not more useful, to disclose that which is not true. The beneficiary is science itself and not the individual. Systematically done, this will eventually result in the elimination of errors of fact or judgment and prevent the repetition of similar investigations that for similar reasons might remain unpublished. Viewed in this manner, a failure is as valuable as a success and therefore just as deserving of publication as the most insightful of findings. Failures often precede success.

"Thanks again for your informative presentation. As a former horticultural extension agent, I understand just where you are coming from."

Henry A. F. Young, President
Young Environmental Sciences, Inc.

Black is the new…black?

Dark foliage and flowers have been popular for quite a while.  Heck, an entire book (Paul Bonine, Timber Press) features the darkest of the dark.

Of course, "black" is a bit subjective.  Dark purple, dark brown, dark green.  But dark is hot; plant breeders and marketers know it. Here’s a few things that have come out within the past couple of years…

Ball Horticulture’s new patented petunia ‘Black Velvet’ is all over the place, along with its cousins, Phantom and Pinstripe.

Bench card from Ball for use in garden centers.  Odd choice of editorial photo for the "little black dress."  Petunia’s cute enough, though.

Centaurea montana ‘Black Sprite’ is a new perennial from Sunny Border Nursery (marketed by Skagit Gardens). You may be familiar with the blue version (Knapweed, Mountain Bluets). I am, because it reseeds all over my stinkin’ garden.  Maybe this one is better behaved.

I snapped this at the OFA Floriculture trade show in July.  Love the black outline on the bud "scales."

A new ornamental eggplant certainly falls under the "black" category.  This super-cute guy was in the "new plants" display at OFA also, but some dork had snatched the tag from the display. Let me know if you recognize it…

Meeestery eggplant has nice flowers and foliage, too. Until the flea beetles come.

There are so many wonderful ornamental peppers out there – all easy to grow from seed.  Most are pretty hot (pop a ‘Black Pearl’ some time for a thrill). From the U.K. breeding company Vegetalis comes the F1 hybrid pepper ‘Chenzo’.

 Like ‘Black Pearl’, the fruit change from black to deep red as they ripen. It’s also hot as blue blazes, with a Scoville rating of 45,000 shu.

Snow – should it stay or should it go?

It’s snowing here in Seattle – always a fun event, especially when we’re expecting up to 10 or more inches. I know…many of you laugh at our “big” snow, but the hilliness of Seattle makes driving in snow an adventure. (In fact, I’m supposed to be flying out tomorrow for a Connecticut presentation, and my flight’s already been cancelled and rebooked. Sigh.)

But what about the plants? This time of year people often ask whether they should leave the snow on their trees and shrubs. I covered this in December 2010 (and in a podcast in December 2011), but now I’ve come up with easily memorized advice:

If it’s light, leave it – if it’s heavy, heave it.

Light snow helps insulate trees and shrubs from winter dehydration, but heavy snow can permanently bend or worse, break, tree and shrub branches. Use a broom or rake to knock heavy snow off branches.

Bending is bad…

…but breaking is worse.

A dirty little secret

Like many, I was interested last week by the announcement that a University of Connecticut professor responsible for some of the research on resveratrol, a plant-based phenolic compound linked to various health benefits, had been accused of falsifying and fabricating data.  According to published reports, UConn officials found 145 cases of faked data that turned up in 26 published research articles by Dr. Depak Das.  Resveratrol occurs in many plants but most notably in grape skins and seeds, and one of the compounds associated with health benefits of red wine.

Needless to say, reports of Dr. Das’s wrongdoing were disappointing to those of us that enjoy an occasional glass of Caberbet Sauvignon or Merlot.  More importantly, although Dr. Das’s research was a relatively minor part of the resveratrol story, these types of reports invariably provide grist for the mill for those that like to question the motives and veracity of scientists.  Only Dr. Das can ultimately comment on his motivation for the con job.  Dr. Das is a tenured professor and head of his university’s Cardiovascular Research Center so presumably career advancement was not a primary factor in the ruse.

In theory, a well designed and well executed study that provides useful results should be publishable.  In reality, the adage that ‘it’s difficult to publish negative results’ often proves true.  I’m not familiar with Dr. Das’s studies or the data he’s reported to have faked, but suppose, for example, he had found that resveratrol did not reduce heart attack risk.  Assuming the trials were experimentally valid, there is still value in that knowledge; it could save others from conducting expensive but likely fruitless research or it may suggest other avenues of research.   Unfortunately, it’s often easier to publish positive results and use those data as the basis for future grant development.  I’m not privy to all the details at this juncture, but I wouldn’t be surprised if this started off as fudging a few numbers, which, in turn, formed the basis for other proposals and started a self perpetuating cycle.

As I noted, Dr. Das is an established scientist near the top of his game.  But the need to keep science clean extends to all levels.  In some regards, the pressure to fudge data is greatest at the entry level.  At research intensive universities, young assistant professors must generate enough grant funding and publications to secure tenure within six years of their hire.  Denial of tenure means time to hit the road.  Many universities are even opting to not reappoint some new faculty at the three-year mid-point review, which was often perceived as a ‘rubber stamp’ in the past.

Falsifying data in science is analogous to gambling in sports.  Both represent the ‘third rail’.  People wonder why baseball came down so hard on Pete Rose.  Once gambling is introduced in sports, fans assume the outcome is predetermined and the sport is done.  Likewise, science runs the risk of becoming irrelevant if the public assumes that researchers are only going to conclude whatever will get them published or help them land the next grant.  It sounds like UConn and the US Office of Research Integrity are preparing to throw the book at Dr. Das.  If he’s guilty as charged, they have to.

Noxious or not? A continuance of the Canada thistle discussion

Ray Eckhart, Master Gardener and loyal blog reader, wrote a long response to Alan’s request for research for the ongoing debate on Canada thistle started a few weeks ago by Jeff. Because he has a lot of links to research in his response, I thought it should have its own posting. So here’s Ray:

Here is a brief summary of the results of a google search of .edu and .gov or .us sites on the subject of Canada thistle or Cirsium arvense as a noxious weed, examining the “whys” by a mostly volunteer* Master Gardener reliant on published literature by reputable sources and charged with fulfilling the Land Grant University charter to bring science based information to the local level.

(* about $6500 of my annual salary and benefits comes from fulfilling Master Gardener responsibilities.)

From the Minnesota pdf referenced above:
“Noxious weeds are difficult to control and injurious to public health, the environment, roads, crops, livestock and property. By law, these weeds must be controlled on all public and private lands.”

From Montana:
“Canada thistle threatens productivity in both crop and non-croplands. In cropland, Canada thistle causes extensive yield losses through competition for light, nutrients, and moisture. It also increases harvesting problems due to seed and forage contamination. In Montana, it is estimated that two shoots per square yard can reduce wheat yield by 15 percent and 25 shoots per square yard can reduce wheat yield by 60 percent. Other Montana crops seriously threatened by Canada thistle include peas, corn, beans, alfalfa and sugar beets. Heavy infestations are also commonly found in overgrazed pastures and ranges and may crowd-out and replace native grasses and forbs, decreasing species diversity in an area.

“By 1795, Vermont enacted noxious weed legislation against Canada thistle and, in the early 1900’s, the currently named Noxious Weed Act gave a person the right to eradicate this species wherever they found it without fear of trespassing.

“In alfalfa stands grown for seed production, Canada thistle can reduce yield by 48 percent. An extra ten percent yield reduction can occur in alfalfa seed production due to seed cleaning. In pastures, Canada thistle reduces productivity by crowding out forage species with spiny leaves that deter cattle from grazing. In non-cropland ecosystems, Canada thistle can crowd out and replace native grasses and forbs limiting land’s recreational use. In gardens, flower beds, and lawns, Canada thistle’s extensive root system makes it a hassle to control. Mowing or pulling this weed is not effective because it grows again from vegetative buds on the roots. In fact, improper cultivation can even worsen Canada thistle problems!”

From Pennsylvania:
“In the Northeast, several weeds including bull and musk thistle, Canada thistle, purple loosestrife (Lythrum salicaria), mile-a-minute (Polygonum perfoliatum), and garlic mustard (Allaria petifolia) are receiving attention [for biological control efforts – ed.] because of their invasive nature.”

2nd Cite for Pennsylvania:
ECOLOGICAL THREAT: Natural communities that are threatened by Canada thistle include non-forested plant communities such as prairies, barrens, savannas, glades, sand dunes, fields and meadows that have been impacted by disturbance. As it establishes itself in an area, Canada thistle crowds out and replaces native plants, changes the structure and species composition of natural plant communities and reduces plant and animal diversity. This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants.

“Canada thistle is declared a “noxious weed” throughout the U.S. and has long been recognized as a major agricultural pest, costing tens of millions of dollars in direct crop losses annually and additional millions costs for control. Only recently have the harmful impacts of Canada thistle to native species and natural ecosystems received notable attention.”

“Some noxious or invasive weeds are highly toxic to equines, however, and can cause tremendous problems if allowed to invade horse pastures. This may be partially due to the extensive taproot in many broadleaf weeds that allow them to remain green longer into the dry season, thereby appearing potentially attractive to horses grazing in poor pastures. This list includes tansy ragwort, yellow starthistle, Russian knapweed, Canada thistle (Cirsium arvense), poison hemlocks, field bindweed, houndstongue, Scotchbroom (Cytisus scoparius), horsetails, leafy spurge, black henbane (Hyoscyamus niger), Klamath weed or St. Johnswort, kochia, yellow toadflax or butter-and-eggs (Linaria vulgaris), silverleaf nightshade (Solanum elaeagnifolium), and puncture vine.”

Colorado: “Canada thistle (Cirsium arvense) is an aggressive, creeping perennial weed that infests crops, pastures, rangeland, roadsides and noncrop areas. Generally, infestations start on disturbed ground, including ditch banks, overgrazed pastures, tilled fields or abandoned sites. Canada thistle reduces forage consumption in pastures and rangeland because cattle typically will not graze near infestations. In 2002, the Colorado Department of Agriculture surveyed counties and while incomplete, the results showed more than 100,000 acres infested with Canada thistle (Figure 1).”

2nd cite Colorado:
“Impacts Agricultural: Canada thistle is an aggressive, creeping, perennial weed. It infests crops, pastures, rangelands, roadsides, and riparian areas (Beck 1996).

“Ecological: Canada thistle spreads rapidly through horizontal roots, which give rise to shoots (Moore 1975). Its root system can be extensive, growing horizontally as much as 18 feet in one season (Nuzzo 1998). Most Canada thistle patches spread at a rate of 3-6 feet/year, crowding out more desirable species and creating thistle monocultures.

“Human: Spiny thickets of Canada thistle can restrict recreational access to infested areas.”

South Dakota:
“Noxious weeds are found in range and pasture as well as noncrop areas and cropland. Troublesome statewide noxious weeds like Canada thistle, leafy spurge, perennial sow thistle, Russian knapweed, and hoary cress can be serious problems in pasture and rangeland.”

“Weeds can reduce the quantity and the stand life of desirable forage plants in pastures and hayfields. These unwanted plants are often more aggressive than existing or desired forage species and compete for light, water, and nutrients. Weeds can also diminish the quality and palatability of the forage available for livestock grazing, and certain weed species are potentially poisonous to grazing animals. The aesthetic value of a pasture is also impacted by weeds.

“The state regulations of the Kentucky Seed Law classify certain plants such as Canada thistle, johnsongrass, and quackgrass as noxious weeds and prohibit their presence in commercial seed sold in Kentucky.”

National Park Service:
“Thistles are pioneer species and are most often found in sites where the ground cover has been disturbed by grazing, erosion, traffic, or other means. Thistles reduce the use of an area for grazing or recreational purposes because of the prominent spines on leaves, stalks, and blooms. Livestock do not eat thistles and will not graze between thistle plants on more desirable forage (Batra 1982).” (linked from .gov sites):
“THREATS POSED BY THIS SPECIES: Natural areas invaded by Cirsium arvense include prairies and other grasslands in the midwest and Great Plains and riparian areas in the intermountain west. Cirsium arvense threatens natural communities by directly competing with and displacing native vegetation, decreasing species diversity, and changing the structure and composition of some habitats. Species diversity in an “undisturbed” Colorado grassland was inversely proportional to the relative frequency of Canada thistle (Stachion and Zimdahl 1980). Canada thistle invades natural communities primarily through vegetative expansion, and secondarily through seedling establishment. Cirsium arvense presents an economic threat to farmers and ranchers. Infestations reduce crop yield through competition for water, nutrients and minerals (Malicki and Berbeciowa 1986) and interfere with harvest (Boldt 1981). In Canada, the major impact of Cirsium arvense is in agricultural land, and in natural areas that have been disturbed or are undergoing restoration (White et al. 1993). In the U.S., it is a host for bean aphid and stalk borer, insects that affect corn and tomatoes (Moore 1975), and for sod-web worm (Crampus sp.) which damages corn (Detmers 1927). In Bulgaria Cirsium arvense is a host for the cucumber mosaic virus (Dikova 1989). In addition to reducing forage and pasture production, Canada thistle may scratch grazing animals, resulting in small infections (Moore 1975).”

Washington State:
“Why is it a noxious weed? Once established, it spreads quickly replacing native plants. It grows in circular patches, spreading vegetatively through roots which can spread 10 -12′ in one season. It poses an economic threat to the agriculture industry by reducing crop yields.”

“Threats: Canada thistle’s rapid growth aggressively competes with native plants and crops for nutrients, moisture and light. It releases chemicals toxic to other plants. The result is a loss of natural diversity. It is known to harbor other pest species, e.g., insects, and has long been recognized as an agricultural est. Both natural and human caused disturbances can create the opportunity for Canada thistle to become established in natural communities.”

“PROBLEM: The extensive root system of Canada thistle allows it to out-compete and displace many native species, especially in degraded prairies where native species are not well established. Spreading both by seed and rhizome, Canada thistle can create monocultures covering large areas. The wind-dispersed seeds may remain viable for 20 years or more, allowing it to spread quickly and making it difficult to eradicate.”

There are more, but I stopped on page 3 of the 120 page result of the google .edu search. I’ll leave it to others more qualified than I am to further debate the relative merits of why or why not a more cavalier (heh!) approach other than current government regulatory action is or is not warranted.