Category: Amusing Facts

Bounce – it’s not just a fabric softening sheet…

…it’s an Integrated Pest Management tool!

[Note added after-the-fact: this was a  tongue-in-cheek bit of  hyperbole – kind of like “it’s not just a Job, it’s an Adventure.” Did not mean to imply that it actually IS an IPM tool. Very badly worded. Hence the beating I took in the comments. Live and learn.]

Fungus gnats (Bradysia spp.) are a pain in the bottom for commercial greenhouse growers. The adults are more of a nuisance than anything else –it just looks bad when a customer picks up your 6” pot of pansies and a bunch of little black gnats take flight.  It’s the larvae that are problematic. Adult females lay the eggs in especially damp growing media, and the newly-hatched larvae feed on the roots. There’s both direct damage and also speculation of easier infection of root-borne pathogens, of which there are plenty. 

 
Fungus gnat larvae, just making a living…

Standard control measures include insecticide drenches, biological controls including a specific strain of Bt (Bacillus thuringiensis – sold as GnatrolTM), nematodes, etc.  One of the easiest control measures is the one I teach my students: to not over-water, i.e. “grow dry”. But that can be difficult in a big greenhouse range with many different-sized containers, all which drain/dry out at different rates. Propagation houses also have high humidity levels and have to stay moist for rooting/germination purposes and are thus favored by fungus gnats.

Entomologist Dr. Raymond Cloyd of Kansas State University and his group were intrigued by Master Gardener anecdotes of dryer sheets repelling mosquitoes, though no research had been done. Could your common Bounce sheet also repel other pests? And, to take it a step further, what, exactly, repels them?  The answers are “yes” and “lots of volatile compounds.”

Their study was published last month in the journal HortScience. Honestly, I’ve never seen descriptors like “controls static cling” and “gives clothes a fresh scent” in a Horticulture journal. Hee! Plus the researchers made it clear this experiment specifically used Bounce Original Outdoor FreshTM. Still kind of humorous, but really good science and the part that’s usually overlooked in the translation to a News Story. Do NOT extrapolate results to include Bounce Spring Fresh, Fresh Linen, and certainly not Downy or Snuggle brands. 

The study had a simple design, releasing lab gnats (ha!) into a  many-chambered container and observing to which chamber the gnats gravitated to (or away from).  There were five different variations on this theme, including an alluringly soggy media sample; when the sample of fabric softener sheet was introduced, they stayed away in droves. All five experiments showed a fairly drastic aversion to the sheet. To determine what was fending off the gnats, they did a steam extraction on sheet samples and ran the condensate through a gas chromatograph – mass spectrometer to measure the volatiles.



Figure from Bounce® Fabric Softener Dryer Sheets Repel Fungus Gnat, Bradysia sp. nr. coprophila (Diptera: Sciaridae), Adults. Raymond A. Cloyd, Karen A. Marley, Richard A. Larson, and Bari Arieli, HortScience Dec 1 2010: 1830–1833

Well, there you have it. Linalool is a monoterpene alcohol found in lavender, basil, and coriander, and is known to be toxic to mites and insects.  Citronello is another monoterpene and lends lemony-freshness to lemon balm, pennyroyal, and rose geranium and has short-term “repellent activity against mosquitoes.”  Benzyl acetate, though not specifically mentioned in the results, is another natural fragrance compound, found in jasmine – and is also an industrial-strength solvent. One man’s solvent is another man’s perfume. Or fabric softener. I bet their lab smelled GREAT, by the way.

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Unintended consequences

Unintended consequences.  When doing one thing causes something you didn’t expect. Many unintended consequence stories in biology start with introduced species. I’m going to skip those here.   I’ve been thinking about unintended consequences recently while trying to figure out what to do about my hops. You see, hops have a nasty habit of getting powdery mildew. That’s one reason why you don’t see a whole lot of hops growing outside the relatively arid Yakima Valley (75% of US production). We started research on hops this year in relatively un-arid Minnesota, and I don’t want our plants to succumb to the dreaded disease. Because we’re growing varieties that don’t have a lot of resistance, and we can eventually expect to get the disease in this environment, I want to develop a way to manage it effectively so we can still do research.  But how do we avoid powdery mildew?  A lot of growers use weekly applications of sulfur.  It’s a nice fungicide for this purpose, and it’s pretty cheap compared to synthetic fungicides.  Great, sign me up for that!  Oh by the way, using sulfur early in the season may cause more spider mite problems later in the season compared to using other, more expensive fungicides.1  Oops, unintended consequence.

One of the most famous examples of unintended consequences that I can think of (OK, other than DDT and birds, or introduced species) is from hybrid field corn 40 years ago.  Detassling corn for hybrid seed production is a hassle, so a modified corn was developed that didn’t produce pollen.  Cytoplasmic male sterility, this technology was called.  Perfect!  No need to hire droves of unskilled labor to walk every acre of seed corn production fields.  Except it turns out that a side-effect of that particular modification made corn especially susceptible to southern corn leaf blight, which damaged a large amount of the corn crop in the early 1970’s.  Unintended consequence. 

 

Imagine the florist’s carnation.  It’s that flower in shades of white to red that you see on boutonnieres and corsages during homecoming and prom, or alternatively, that flower dyed green for St. Patty’s or blue to match Grandma’s hair.  Before breeding for increased longevity / vase life, carnations had a noticeable smell.  When breeders ignored fragrance, or possibly even unknowingly selected against fragrance (fragrance may decrease flower longevity), they made carnations that are just kinda pretty looking, and that’s about it.  Unintended consequence.  Now researchers are trying to figure out how to get fragrance back into flowers (and even into flowers that never had much in the first place).2

 

Here I will steal from a somewhat confusing speech of recent past, and turn it into somewhat confusing text to fit my story.  Unintended consequences are usually a result of ‘unknown unknowns’.  We don’t know even know what questions to ask (“Yes, I’m using sulfur to kill powdery mildew.  So what?”).  Turning an ‘unknown unknown’ into a ‘known unknown’, or something that we know we don’t know but can hopefully find out, takes an open mind, a keen eye, and creativity.  Like “hey wait a minute, now that I’m using sulfur on my hops, I seem to have more problems with spider mites.  I wonder if there’s a connection…”  That’s still unknown, but at least it’s a ‘known unknown’.  Turning a ‘known unknown’ into a ‘known’ takes science, and making it widely ‘known’ takes people who keep up to date on science and are good at writing or speaking.  Hooray for research and extension!
1 Gent et al. 2009. Effects of powdery mildew fungicide programs on twospotted spider mite, hop aphid, and their natural enemies in hop yards.  J. Econ. Entomol. 102(1):274–286.
2Vainstein et al., 2001.  Floral fragrance: new inroads into an old commodity.  Plant Physiol. 127(4):1383.

 

A sustainable resource? Oh, for peat’s sake!

Recently a well-known gardening blog featured a guest posting by a garden writer who made a case for using Canadian sphagnum peat moss as a horticultural amendment.  He defended his preference through “facts” provided by the Canadian Sphagnum Peat Moss Association.
This is kind of like relying on the petroleum industry for the most objective information on the environmental effects of oil spills.  Or the tobacco growers association for data on the effects of smoking on human health.  C’mon now.  We know we should consider the source of our information, right?
This isn’t to say that industries don’t have their own scientists conducting research, or that their research is unreliable.  But to depend on industry talking points alone ignores the vast body of information provided by independent university researchers.
Several years ago I reviewed the scientific literature on the topic of peat as a sustainable resource; that column can be found here as well as in my most recent book (The Informed Gardener Blooms Again).  Rather than repeat what I wrote there, I’ve conducted a quick overview of the research conducted on Canadian peatlands published in the last 10 years.
There are many such articles.  And in general the results are not positive.  Here are some of the highlights (or lowlights):

  • Peat harvesting permanently alters the hydrology of bogs so that natural regeneration is impossible
  • Sphagnum does not easily regenerate on degraded peatlands, causing the sites to become drier over time
  • Species composition of harvested peatlands is not the same as on undisturbed peatlands
  • The mulches used in peatland regeneration decompose and become significant sources of carbon dioxide
  • Natural peatlands are long-term sinks of atmospheric CO2, while mined peatlands increase atmospheric CO2 levels
  • Amphibian populations, already hampered by acid deposition, are further threatened by peat mining
  • Volunteer birch trees on abandoned peat mines accelerate water loss

If we, as gardeners, deliberately choose to use unsustainable natural resources, we need to be fully aware of the consequences.  Unquestioned acceptance of industry talking points lends nothing to the discussion.

Of Worms and Fertilizers

Today I’m going to write about fertilizers and worms.  The purpose of this post is not to encourage you to use fertilizers.  I agree wholeheartedly with Linda’s post – we don’t need many of the fertilizers which we’re using.  Still, it’s important to know the facts about anything that you’re doing (or not doing) to and for your garden, and to do them (or not do them) for the right reasons.  With that in mind, I’ve been reading about worms and fertilizers for the last few days and wanted to let all of you know the basics of what I’ve been reading, because it is somewhat contrary to what many gardeners believe.

Before we begin let’s get one thing straight — worms are basically good for your garden and your plants in general.  We like them!

Over the years I’ve heard all kinds of comments about how inorganic fertilizer is bad because it kills worms or drives them away.  For the most part I’ve just accepted these claims as generally true because it seemed to make sense and I didn’t have a reason to study it further (I don’t write about worms much, and I’ve never spent any time doing research on them – still, I have to admit that this is no excuse for ignorance).  The only contrary words I’d ever heard spoken about the reality of what fertilizers do to worm populations had come from a soil scientist friend of mine who told me, in casual conversation, that he didn’t believe that fertilizers were bad for worms at all, except, perhaps in the very short term if they got some fertilizer directly on them.  Rather, he believed that, because fertilizers encouraged the growth of plants, fertilizer use would actually increase worm populations because it would increase their food supply.

After reading through a few papers it looks like my soil scientist friend was right.  Here I’m going to summarize my general impressions about these papers into a few sentences – not exactly fair because the relationship between worms and fertilizers isn’t completely straightforward – but hey, this is a blog!  Basically, if you add fertilizer of any sort to your soil you will ultimately increase worm populations because you will encourage the growth of more plant material.  More plant material, over the course of time, means more organic matter for worms to eat.  Generally organic fertilizers seemed to be preferred by worms (probably because they include lots of organic material along with the nutrients which they offer), but overapplication of fertilizer (organic or inorganic) could be bad for worm populations, at least in the short term.

So, in a nutshell, judicious fertilizer use shouldn’t affect worm populations negatively.  Still, why add fertilizer at all if you can avoid it?  Mulch and compost – worms will definitely enjoy that!

Fertilizers, crops and landscapes

Last week Jeff wrote about the dangers of using “balanced” fertilizers, especially in reference to phosphorus content.  Comments quickly followed about using fertilizers in many situations – on farms, in container plants, on trees – and so on.  One of the latest comments came from Nick and began “I don’t usually recommend fertilizer for perennials or woody plants to consumers. In most cases they aren’t needed.”  And this leads into today’s topic.

Many of the horticultural practices we use in our gardens and landscapes have, unfortunately, been derived from agricultural crop production.  Whether you’re growing a field of wheat, garden tomatoes, or containerized shrubs your goal is maximizing crop production.  By its nature, this is an unsustainable practice because it requires continual inputs of water and nutrients at higher levels than would naturally occur.

But this is not how you should care for landscape trees and shrubs, and why Nick’s comment was a good one.  You don’t need to routinely add fertilizer to these plants; they don’t need it to grow normally.  What we should be doing in landscapes is preventing nutrient deficiencies.  Once you have a soil test in hand, you’ll know what nutrients may be too low (or too high) and how soil pH will affect that.  For most of us, this may involve occasionally adding one of a few nutrients (most commonly nitrogen), or perhaps acidifying the soil to improve nutrient availability.

 How do you know when to add nitrogen to established landscape plants?  Let your foliage do the talking. If leaves are uniformly yellow, small and sparse, you might have a nitrogen deficiency.  This will be most common in the mid to late summer, when plants are growing most rapidly and competing with one another for resources.  Be sure this symptom is wide-spread, however.  If it’s just one plant showing deficiency symptoms, it’s probably not a landscape issue.

 

Potted plants…really potted

A week or so ago my new friend Doug wondered about some gardening advice on the radio: would adding vodka to paperwhite narcissus make the flowers less “floppy?” The explanation he’d heard was that alcohol would burn the roots and reduce stem growth. Then today I received an email newsletter with the same intriguing information. This newsletter referred to a 2006 article that appeared in HortTechnology as the source of this information.

The study by Miller and Finan has generated a lot of interest in the gardening community, especially this time of year as people get ready to force bulbs for indoor blooms. Unfortunately, that enthusiasm isn’t evident among researchers. Neither the original authors nor any other researchers have continued this work; the HortTechnology paper has never been cited in any subsequent publication.

This is unfortunate – because inquiring minds want to know WHY alcohol causes narcissus stems to be shorter. Miller and Finan hypothesize that it’s simply an osmotic effect and allude to preliminary data that support this, “but additional work will be needed for confirmation.”

So I’ve looked into other scientific articles about ethanol and roots for insights into this phenomenon. There’s nothing on narcissus, but others have studied trees, forsythia, tomato and barley reactions to root-zone ethanol. In all of these cases, exposure to ethanol resulted in reduced root growth, decreased water uptake, and reduced leaf transpiration.

How does this translate to shorter stems and leaves? A reduction in water uptake and movement through the plant – that is, from roots through the stems and out of the leaves – can reduce movement of growth regulators like cytokinins from roots to stems and leaves. It can also mean that the plant contains less water and is less turgid as a result. Both growth regulators and cell turgidity are important in cell division and elongation. Reduced cell expansion will cause stems and leaves to be shorter and/or smaller as a result. This same phenomenon can be seen in plants grown under saline or droughty conditions: these plants are always smaller than their normal counterparts.

So what your grandmother used to warn you about is true – alcohol WILL stunt your growth!

When You Gotta Go, Go Green

Here’s a bit of the fact-filled, intrepid reporting we at Garden Professors are pleased to provide.

Just back from a visit/droolfest to Pennsylvania’s "Golden Triangle" of horticulture: Swarthmore’s Scott Arboretum, Chanticleer, and Longwood Gardens. 

At closing time on Saturday, I was wandering through the cavernous halls of the Longwood conservatory, looking for either my travel companion John Greenlee (Mr. American Meadow Garden), or the restroom.  Found one, then followed the signs to the other…

Whoa.

And it keeps going, way on around the bend.

Unveiled just a week prior, the green wall system was designed by GSky Plant Systems. At a little over 4,000 square feet with 47,000 plants, it’s now the largest green wall in North America. 

The modular panel system is very clever:

Plants are held in place by a geotextile surrounding a fiber substrate. Computer-controlled drip irrigation is woven throughout the entire structure.

Except for the glass ceiling, the corridor is subterranean. Perhaps because it was closing time and mostly empty, we found it just a tiny bit unsettling. John flailed about, muttering something like "Soylent Green is people!" 

Anyhoo, it was very grand and inspiring. In case you’re wondering what was behind all those shiny steel doors: 

 

Folks, you can’t get this kind of in-depth information on just ANY garden blog…

Happy Days

Today is such a good day.  Really good.  Almost as good as my wedding day and the birth of my kids good.  Better than the Eagles won the Superbowl good (I’m a big Philadelphia Eagles football fan — Mike Vick and his transgressions aside of course).

Just for today I don’t care much about the arguments for or against organics, natives or even my favorite topic, pesticides.

What’s the news you ask?

Peanuts.  Hot Boiled Peanut.

If you follow this blog you may recall that Tom Michaels, a professor and bean breeder here at UMN, and I planted a few rows of peanuts last year in between rows of trees — the trees you see below are elms from a selection program we’re running here.  Between the rows you’ll notice some plants starting to turn yellow, those are peanuts.  The darker green plants between the rows of trees are canola.

Below is what a peanut plant looks like when you harvest it.  After the flowers are pollinated the plant sends the stalk on which the flower is growing into the soil where it forms a peanut.  When we harvested we saw anywhere from 0 to about 10 peanuts per plant.

We harvested a test batch of peanuts last night — probably a little over a pound.  They were a little immature, but they still tasted good fresh out of the ground.  Without any treatment fresh peanuts taste a lot like fresh peas — an unmistakable “legume” flavor.  For those of you love roasted peanuts, that familiar flavor is a result of the roasting process.

Boiled peanuts are a little different than roasted peanuts in that the pods are usually harvested a little bit immature, so our first harvest, yesterday, was actually right on time.  We’re planning on finishing harvest next week.

Anyway, once we got the peanuts out of the ground I drove them straight home, put them into a quart of water, added a quarter cup of salt, and put that mixture into a crock-pot on high heat for three hours and low heat for another eleven.  I tasted one after three and knew they would be good.  After the full 14 hours?  The best boiled peanuts I’ve ever had.

As my wife noted, these peanuts aren’t exactly the same as the one’s you get in
the South.  She was trying to be nice — but I got the impression that
they were just a little too different from what she’s used to for her to like them quite as much as
the ones we get when we visit South Carolina (which we visit yearly). The difference between these peanuts and the other boiled peanuts that I’ve had (and I’ve had a lot — from all over the South) is that these are a little bit sweeter.

For me — Best damn peanuts ever — Minnesota grown no less.  Who woulda’ thought?  Not me.  Can’t wait to boil a big batch next week!</d

Why I like science (our visiting professor returns)

I like science.  I see it as a way to figure things out.  It creates a combination of a) things we’re pretty sure of (facts about the shape of DNA, the optimum pH for certain plant species, and theories consistent with such facts, for example) and importantly, b) questions we can ask next.  When research is designed to answer those new questions, the results will either support the things we’re pretty sure of and lead to an expanded understanding and new questions, or they won’t support what we thought we knew and the results will lead to a different understanding and new questions. 

Scientists do research, but it’s only useful if others find out about it.  Imagine what more Darwin might have come up with had he known about Mendel’s work on inheritance of traits.  And when a researcher shares his or her research results at a meeting or in a publication (like many colleagues got to do in Portugal last week, lucky dogs), they are opening their research up to critique from others.  Thoughtful critique is exciting.  It may feel like an attack on the researcher, but it is usually an attack on the borders of what is known. 

Stay with me, this relates to professors AND gardens.

One of my favorite papers full of criticism is about ‘Talking Trees’.  This idea emerged in the early 1980’s (and given a catchy name) when research was suggesting that trees with damaged (manually torn) leaves could cause chemical responses in nearby plants.  It was concluded that maybe, just maybe, one tree was acting as a beacon, sending out signals when damaged by a herbivore.  Then a tree fortunate enough to receive the signal could begin to mount a defense against herbivores before being damaged itself.  A paper published in 1983 (Baldwin and Schultz, Science, 221:277–279) showed evidence for this kind of communication.  But then an article published in 1985 [Fowler and Lawton, American Naturalist, 126(2):181–195] called into doubt the conclusions of the 1983 paper.  As the authors of the 1985 paper lay out, the statistical design and analysis of the 1983 paper was flawed.  We shouldn’t trust the conclusions without more research.  And one thing I really like about the new research detailed in the 1985 Fowler and Lawton paper, they clearly lay out potential shortcomings of their own work, and even consulted about these pitfalls with an author of the 1983 paper (which they thoroughly criticized!).  This is where the “what questions to ask next” are generated, and the authors did some of the heaviest lifting for us there.  Such discussion and disclosure helps to expand knowledge in the field, but I like it in this particular instance because it also gives a sort of narrative about thoughtful criticism in science.

So this does relate to gardening, because there is a lot more going on out there than just ‘growing’.  There has been a lot of research since 1983 on inter-plant signals, and it does seem to happen in the lab, but also at close distances in nature with some plants (the sagebrush-tobacco relationship is best-studied).  The research has also shown this signaling can reduce herbivore damage on undamaged plants.  For brief reviews, see Dicke et al. [Trends in Plant Science, 2003, 8(9):403-405] or Baldwin et al. (Science, 2006, 311:812–815).  And as an added bonus, the chemicals released by herbivore-damaged plants can attract carnivores that EAT herbivores (predatory mites and parasitoid wasps, for instance).  Some of the chemicals that may be involved in these responses?  Methyl jasmonate (smells like jasmine) and methyl salicylate (wintergreen oil).  Your garden is doing a whole lot more than you realize just under your nose, and I haven’t even MENTIONED all the plant and invertebrate sex, or the kinky inter-kingdom pseudocopulation that might be going on out there.  Plants and science are awesome. 

Pigmented Mulch in Paradise

Just back from a quick vacation to Little Cayman island.  Truly a dot on the map – the whole island is about 7 miles long and a mile wide. Only 150 locals and a couple hundred tourists are on island at any one time.  It’s beyond laid back, with few attractions other than the resident iguanas and red-footed boobies (booby jokes abound).

Airport terminal/post office/fire station.

The big draw is diving – LC is the home to Bloody Bay Wall, one of the most famous dives in the Caribbean.  The reef drops off like a sheer cliff, from 40-60′ to more than 1000′.

All the action is underwater!
(Let me know if you want to see more slightly blurry diving photos.)

“Fascinating, Holly.  But what does this have to do with painted mulch?”

The extent of the landscaping for most yards: conch shells arranged in interesting designs and/or piles. But as we pedaled past a rather upscale condo, I came to a screeching halt. A gorgeous Bismarckia nobilis had caught my eye, but then I saw what was under it. Egad.

Everything comes to Little Cayman by a weekly barge or little prop plane and is wildly expensive. Four-pack of batteries? $15. A six-pack of beer is $20. TWENTY DOLLARS!!!

So, good readers, what we have here is possibly the most expensive mulch on the face of the earth. I can’t even imagine.


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