Amusing Facts – Page 11 – The Garden Professors™

Visiting Professor guest post: Organic foods

There are lots of reasons consumers give for buying organic foods, but a few reasons are very common. Among them is the notion that organic foods are better for you. Really? Are organic fruits and veggies better for you? Depends on what you mean by ‘better for you’. But as far as we know, the answer is probably ‘no’, especially if you’re buying organic fruits and veggies (F&V) at the store. It might seem crazy, but there’s no good evidence to support the notion that you will be more healthy by shopping for organic F&V. There are some complicated reasons for this, and some areas we aren’t quite sure about yet, but I’ll try to explain.

If ‘better for you’ means ‘fewer pesticide residues,’ you’re right. But if you think ‘fewer pesticide residues’ means ‘better for you,’ that gets murky. Why do we apply pesticides? We do it to protect our food from pests and diseases. It’s cheaper and more productive than destroying blight-infected tomatoes, individually wrapping apples in a protective barrier, or throwing away heads of cabbage with worms. But why do those things matter? It turns out we’re just consumers. Two big things we look for when buying F&V are appearance and cost. If a person has a choice between a spotty, more expensive apple and a uniformly bright and shiny lower-cost apple, he’ll probably choose the latter. And which would be better, buying 2 heads of cauliflower because it’s pretty and low-cost (conventional), or buying one head because it has a slight cosmetic defect and costs a little more (organic)? You guessed it; in terms of your health, it’s more likely that 2 heads are better than 1. If that isn’t complicated enough, consider that there are no good long-term human studies concerning the health effects of pesticide residues ingested from food. There’s no evidence that eating conventional F&V, even with the elevated risk of consuming more pesticide residues, is worse for you than eating organic F&V. But there is evidence that eating more F&V is better for you than eating less. So why eat less?

Some of the best health care in Minnesota comes from the Mayo Clinic. What? Who cares about the Mayo Clinic? In Minnesota, we worship the Mayo Clinic. [undeserved pride] They represent some of the finest health care in the country [/undeserved pride]. And what does the Mayo Clinic have to say about pesticides on our food? “Most experts agree…that the amount of pesticides found on fruits and vegetables poses a very small health risk.”

But what about nutrients—don’t organic foods have more nutrients or something good in them? Maybe they do have fewer nitrates (which may be bad for you, especially if you’re too young to read this), but that really depends on how the specific growers use fertilizers. Maybe some organic produce tends to have more vitamin C, but that can vary too. And even if the organic tomato you’re eating has more vitamin C than the conventional tomato you passed up, is that physiologically relevant? Does it matter to your body? We don’t have any good evidence that it is.

Why am I being so down on organics? Mostly because I like to play devil’s advocate. I buy a lot of organic F&V. There are some reasons to buy organics that may be more legitimate than “it’s better for me”. Sadly, research seems to indicate that I buy organic F&V to make myself feel good for buying it, not because it’s actually better for me. But in general, eating healthy means eating more fruits and vegetables.

Charlie Rohwer is a horticultural scientist at the University of Minnesota Southern Research and Outreach Center. He has an MS from Michigan State University and a PhD from the U of M. He currently studies vegetables and things that make them good for you.

Short tree syndrome solved!

Good answers from Kenny S., Jimbo, Joe Schalk and Diana! You were all skirting about the phenomenon of thigmomorphogenesis – or touch-induced change (also discussed in Jeff’s post of January 7. The tests in the GP’s class are cumulative!). In this case, the touch is wind. Edge trees (or corn stalks) are more exposed and receive more wind, resulting in stunted heights and increased trunk diameter (you can’t see this last characteristic in the Friday photo). Trees in the middle of the stand aren’t exposed to wind buffeting and put their resources into increased height. Similar stunting and thickening can be seen in urban plantings along the edges of sidewalks or anywhere people or animals routinely walk.

I spent my grade school years in a 1950’s housing development that had been Douglas fir (Pseudotsuga menziesii) forest. The developers left many of the trees standing, and our backyard was full of tall, skinny and isolated Douglas firs. When the Columbus Day storm (an extratropical cyclone, of all things) hit the Pacific NW in 1962, seven of these trees came down (none hit our house, fortunately).

Now of course a cyclone will take down many trees, regardless of their location…but this continued practice of leaving trees standing alone during development often results in blowdown or breakage of these now unprotected trees.

Last-Frost-Date Roulette

We all play the game – at least the more impetuous among us do. You sneak a few tender things out into the garden, or on to the patio. When the temperature drops and there’s a frost warning, no problem…just cover them up or bring them in.

Unless you forget.

This WAS a rare and neato Pereskia aculeata ‘Variegata’. Paul W., please send me another…

Before dawn on Monday morning, (May 9) the temperature on our little mountainside dropped below freezing for four hours, going as low as 29.5 F according to our weather station. I had tucked everything back into the greenhouse or up under the eaves…except for the contents of a built-in planter on a far outpost of our deck.

Top o' the frosty mornin' to ya...
Dahlia Mystic Desire, edged in frost at 7:00 a.m., May 10.

NOAA has a handy set of maps that illustrate last dates of “Spring freeze occurrence”. The maps present data averaged between 1951 and 1980.

Walking around the garden last evening with a nice hot cup of martini, I surveyed the damage. Big, juicy-stemmed bleeding hearts that seem so fragile and succulent? Not a speck of injury – but they’ve been up since March. Newly emerged (and really expensive) Asian Jack-in-the-pulpits looked like wet rats. Annuals and tropicals exposed out in the open didn’t stand a chance. Early-to-leaf-out trees can take a beating, too. Japanese maples are notoriously precocious, flinging their fabulous foliage out as much as 45 days prior to last frost here. They’re in pretty good shape now, having acclimated a bit. But for our previous hard frost,15 days ago, we had eight little maples individually draped in white row cover (looked like Halloween).

No longer desirable...
Dahlia Mystic Desire, kaput at 7:00 p.m., May 10.

So why the damage on some and not others? Plants differ in the amount of sugars, proteins, and other compounds that affect the osmotic potential in cells. The lower the content of these compounds, the more likely freeze damage will occur. Young and unacclimated tissue tends to have a higher ratio of water. Like an overfilled water bottle stuck in the freezer, something’s got give as the liquid crystallizes and expands (vast oversimplification, sorry). Cells burst, or are crushed from the freezing of intracellular water, and fluid goes everywhere – hence the limp, dark, water-soaked appearance.

Fog or dew on the plant can delay injury; as external moisture freezes, in gives off heat (an exothermic reaction; one of the amendments to the Laws of Thermodynamics), until all the water is frozen. This is why citrus groves are continually sprayed with water during a freeze event. So it also depends on the duration of the cold; if temperatures just briefly drops below freezing, damage is minimal. Four hours for non-acclimated tissue? See the grim photos for results. Will I wait until May 15 to plant stuff out next year? Absolutely, positively, not. We’re due a no-late-frost spring!

Do These Come In Control Top?

For those color-conscious gardeners who can’t bear to have visible tomato ties (or panty lines):

Only $2.99 for eight pieces? Whatta deal!

Do you know how many tomato ties you can get from a pair of hose? Especially if you are a “long”? About fifty. Of course they’ll be nude or black, unless you bought into that purple trend last season.

Yeesh.

ps: I do like Lusterleaf’s (company responsible for the above) can o’ twine with the handy cutter-top, though. $4 and it has lasted through several seasons.

Thieves purr

Today I found a cool website – it’s an anagram generator (http://wordsmith.org/anagram/). The title of today’s post is the first of the 553 anagrams generated from the word SUPERthrive.

I’ve been getting free samples of SUPERthrive for a long, long time. For those of you living on a remote desert island, SUPERthrive is a product invented and sold by “Dr. John A. A. Thomson (in 27 different title Who’s Who Directories),” according to one of the promotional flyers. The same flyer features Nick Federoff (“ ‘Most Listened-to’ Radio Garden Expert”), who says of Dr. Thomson “he has saved far more trees than anyone else in the world.”

Space constraints and my patience limit how many of the product claims I can include. Here’s one from the package: “Dozens of the world’s science miracles in each drop!” Well, what are these science miracles? The only identified compounds on the label are Vitamin B-1 (which plants make themselves, and which I’ve written about here), and NAA, an artificial auxin used as a rooting hormone. The rest are mysteriously referred to as “crystalline compounds of C, H, O.”

Since this product has been around since 1940, there should be plenty of documented research on its efficacy. But thorough searches of the plant science databases turned up only two: one on growing hydroponic orchids (where SUPERthrive is used as part of the experimental protocol but not as a treatment) and one on rooting stem cuttings of Intsia bijuga, an Indo-Pacific tree in the pea family. Sadly, SUPERthrive was not as effective in promoting rooting as were traditional rooting hormones (IBA and NAA). An online research report from TAMU found SUPERthrive to have no effect on cotton. Even California Science Fair participant Chingiz R. Bigalimov was disappointed that SUPERthrive did not enhance rooting of narcissus bulbs.

Why would Dr. Thomson, who “by 1979 had received a Ph.D in biochemistry and nutrition, and a Doctor of Arts in biochemistry and horticulture,” claim that SUPERthrive is a “billions-proven extra-life-maker” without the science to back this up? I tried to find more information on Dr. Thomson’s doctoral research at Columbia Pacific University (an unaccredited distance learning school in California), but it had been closed by court order in 2000 for, among other things, failing to employ duly qualified faculty and failing to meet various requirements for issuing PhD degrees.

I think all of us GPs would agree that if you like a product and it causes no harm, more power to you. But please consider these last few caveats, especially if you are a Master Gardener or garden professional:

There is no established science supporting the use of SUPERthrive;
NAA is an artificial rooting hormone classified by the EPA as a pesticide, making SUPERthrive an unregistered pesticide. Some states ban the sale of this product.

Think I’ll go play with the anagram maker some more…

Products!

Just returned from a mega field trip across the state of Virginia with my Ornamental Plant Production & Marketing class. We toured major wholesale nurseries, greenhouses, and retail garden centers over the course of three days. The trip went well, I believe (university field trips are a considered a success if you return with the same number of students you left with).

One over-arching trend is, of course, that growers and retailers are going after the veg/fruit thing in a big way. Bonnie Plants has been one of the few vegetable transplant growers for the big box stores; now others are getting in on the act. Wholesale growers who traditionally supplied woodies and perennials to independent garden centers are including veg plants and herbs in their product mix.

Even the packaging is changing from the ubiquitous paper cup or poly 6-pack. Coconut fiber (coir) pots are a step up from peat pots – they hold up better for the grower and garden center but are still plantable or compostable.

'maters

I can’t decide whether these pre-planted bean cages are ridiculous or genius. The students rated them “very cool”. But how many beans can you get off of three plants?

bean thingies

Take some galvanized tomato cages, paint them bright colors, and charge three times the usual price. Who on earth would go for this? Oh wait, that would be me. Two. In orange. Cram ’em in the van, people.

I must have eet

Baffling Daffs

It is daffodil season in the Northern Hemisphere, hurrah! May their blooms shoo away the gray of winter! It is also the season where everybody and their mother writes something about the wonders of the genus Narcissus, so figured I’d join the fray, but with a bit of a chip on my shoulder…

Miss ‘Barrett Browning’ in the Hahn Horticulture Garden at Virginia Tech

I recently read YET ANOTHER article warning against mixing daffodil stems in with other cut flowers due to “harmful effects from the sap”. If stems are conditioned, that is, placed in warm water on their own for 12 to 24 hours, it’s supposed to be o.k. This is repeated in everything from floral arranging manuals to gardening articles, but they never say what exactly causes the problem. So I’ve combed through many resources, to find a specific study backing this up and identifying what compound is responsible.

Known:

1) There is such a thing as “daffodil picker’s rash” which has been reported in the journal of Contact Dermatitis (Julian and Bowers, 1997). The authors attribute this rash to the “crystals of calcium oxalate in the sap, in conjunction with alkaloids, [which] act as an irritant, and also cause the characteristic sores.” Duly noted.

2) Said calcium oxalate crystals are found throughout the daffodil, in the bulb, stem, sap, flowers, etc. Micrographs show that these crystals are needle-sharp, and apparently very painful (I have not gotten up the nerve to give them a nom). This is why deer and bunnies will not eat your daffs.

3) The list of alkaloids is fairly extensive (as with many other members of the Amaryllidaceae family), including masonin, homolycorine, and a real nasty one, narciclasine- which disrupts cell division (meiosis) much like colchicine.

4) Are daffodils poisonous? Yes. If you (or your cat) hunkered down and consumed an entire bulb, problems would ensue. But the calcium oxalate crystals are, perhaps, nature’s way of convincing you (or Mr. Twinkles) that this is not a good idea.

So is there really an effect and if so, what makes daffodil sap deleterious to the other flowers in the vase? The study “Effects of Daffodil Flowers on the Water Relations and Vase Life of Roses and Tulips” by W.G. van Doorn appeared in the Journal of Horticulture Science. Dr.van Doorn found the mucilage (sap) was indeed to blame, with just one daff shortening the vase life of both the tulips and roses by almost half. But what component?

He split out the alkaloid fraction and the sugar fraction of the sap, and then added them as individual components to the vase water. He drew different conclusions as to the cause: the research indicated that the effect in roses is mainly due to the sugar and polysaccharide fraction of the mucilage stimulating bacterial growth. This clogged the rose’s vascular system resulting in bent neck. You’ve seen this before – the bud, yet to open, flops over, never to recover.

These same sugars didn’t impact the tulips negatively but the alkaloids sure did. Even touching the sap to the tulip foliage produced a yellow spot. He was not able to distinguish which of the six alkaloids detected were responsible, but at least narrowed down the cause ( sounds like a job for a grad student!).

So there you have it. I feel better. Am off to pick a few daffodils (very carefully) to brighten my office.

You say tomato, I say phytochrome

Yesterday I got an interesting email about a new product – a Tomato Automator. Briefly, this square, red plastic disk slips around the stem of a tomato plant to suppress weeds and pests. Most intriguingly, we’re told that the color “triggers a natural plant protein that makes tomatoes mature faster and product more fruit.”

Given this is a red product, it’s likely that the protein referred to is phytochrome (literally, “plant pigment”). Phytochrome activity is maddeningly complicated to explain, so we’re going to keep this simple and refer (somewhat inaccurately) to “active” and “inactive” forms of phytochrome. The active form of phytochrome exists when red light is predominant and encourages leaf expansion, chlorophyll development, and other characteristic of plants growing in full sun. In contrast, the inactive form of phytochrome occurs when red light is reduced, either at night (when there’s no light) or in shaded conditions, where far-red light is predominant. (Far-red light occurs just outside our range of visual perception but is absorbed by phytochrome.)

From a practical standpoint, this means a plant can “tell” whether or not its light environment is limited: both red and blue light are absorbed by chlorophyll, so a low level of red light means poor photosynthetic conditions. Under such conditions, “inactive” phytochrome causes many plants to become etiolated (have abnormally long stems) in an attempt to outgrow the shade before it starves from lack of carbohydrate production. In addition, this photosynthetically-poor light environment can also increase fruit set by redirecting resources to seed production rather than foliage – perhaps a plant’s last effort to reproduce before it dies.

OK, now onto the useful application of this information. Several years ago researchers investigated that effect of different colored plastic mulches on tomato production. Again, to keep this simple we’ll just focus on the effect of red mulches. It’s pretty much agreed that red plastic mulch reflects both red and far-red light, increasing not only red light but paradoxically the relative levels of far-red light. Theoretically, this shift would cause tomatoes to put more resources into fruit production, and indeed some studies found this to be the case.

Unfortunately, the phenomenon is not consistent throughout repeated field studies. Some of the other confounding factors are soil temperature (warmer temperature = more growth), insect and disease pressure (both decrease tomato production and are variably influenced by mulch color), and the fact that ethylene production (the plant growth regulator responsible for fruit ripening) is not controlled by phytochrome at all.

So are Tomato Automators worth the trouble? Probably not, especially if you have many plants requiring many automators.

I’m Saving Myself for Pollination

Let’s take a very brief respite from the socio-religious implications of science, soil testing, and compost tea to ponder a more lighthearted topic. I need a bit of a morale-boost.

You: “O.K. Holly, Spring’s allegedly coming…how about a closer look at some wildflowers?”

Me: “Done!” (fingers snapping)

For a short time in March, forest floors across Eastern North America can be absolutely littered with a multitude of sparkling white flowers. This very cool little plant, Sanguinaria canadensis, is one of the first wildflowers to emerge in the spring and colonizes deciduous and mixed woodlands.

Flock of bloodroots, open for business at the fabulous Mt. Cuba Center.

A member of the Poppy family, Sanguinaria is a monotypic genus; that is, there’s only one species. Commonly known as Bloodroot – mostly. However, S. canadensis is also known as (and I quote): Bloodroot, Red Puccoon, King Root, Red Root, Red Indian Paint, Ochoon, Coonroot, Cornroot, Panson, Pauson, Snakebite, Sweet Slumber, Tetterwort. Large Leaved Sandwort, Large Leaved Bloodwort, plus whatever else Aunt Minnie “knowed it by”.

As one of the first wildflowers out of the ground, it’s still darn cold when the Bloodroot flower appears, and they’re quite protective of their private parts. The one leaf emerges at the same time and cups around the flower, helping to protect the fragile blossom from wind, rain, and snow. The petals also close up at night to save the pollen,since in most locations it’s so cold that few insects, save the occasional fly or beetle, are out and about. And as a last resort, they can just “do it themselves”, better described as self-pollination.

I have been pollinated! Victory is mine!

If you break off a stem or piece of the root, out will ooze a reddish-orange juice, hence the common name. It’s been prescribed for myriad conditions by Native Americans and herbal practitioners. One of the more interesting properties is that the sap is an escharotic – it kills tissue. Ironically, according to herbal lore, to draw love to you, wear or carry a piece of the rhizome. If attempting this bit of magic, maybe it’s best not carried in one’s pants pocket.

My Favorite Drug

I love coffee, but I’m not a big coffee drinker. On average I probably consume a cup of coffee every week or two. Why don’t I drink it more often? For a few reasons: First, I’m too jumpy/jittery/nervous to begin with and I don’t need this stuff making it worse, second, it tends to upset my stomach if I haven’t had a meal beforehand, and third, while I like regular coffee, the stuff that I really love are those insane fru-fru coffee drinks that you can only get at specialty shops for five or six bucks — which seems like a waste of money to me. As you may have guessed, at this very moment, I have an overwhelming urge for a vanilla latte and so, in lieu of that, I have decided to submit this post.

Anyway, as most of you know, coffee is a horticultural crop, and so are most of the other sources from which most of us obtain our (legal) chemical stimulants like chocolate and tea. What most people don’t realize is that the stimulants in chocolate and tea are actually somewhat different than caffeine. Chocolate does contain some caffeine, but its major stimulant is the closely related theobromine (which doesn’t actually have any bromine in it…). Tea (which also has very low amounts of caffeine), on the other hand contains the stimulant theophylline which is, again, closely related to, but not the same as, caffeine.

What blows me away about caffeine is how toxic it is. If caffeine were a pesticide it would need to be labeled as category 2 (there are 4 classes with 1 being the most toxic). Its LD50 (in other words, the amount of this chemical that, if fed to a person, would have a 50% chance of killing him/her) is estimated at about 75 milligrams per pound that a person weighs. According to Starbucks website, one of their tall vanilla lattes contains about that much caffeine, and so you could assume that a 150 pound person could kill themselves by drinking about 150 lattes (or 150 of the smaller cups of espresso from which the coffee is made). Additionally, though findings are inconsistent, caffeine has been linked to certain cancers. The current thinking is that it may affect hormone levels in the body which, in turn, influence hormone related cancers like breast cancer, etc. This research is far from conclusive, but it is concerning.

OK, so here’s the thing that’s interesting to me. There is a small but real contingent of people out there who want to ban the herbicide 2,4 D (I picked 2,4 D randomly – I could have picked Round-up, Sevin, or any other pesticide – but I was thinking of summer, and so 2,4 D, the most commonly used turf herbicide, is what I chose). I’m no fan of 2,4 D and would love to see it used less frequently than it currently is, but it is a useful herbicide, particularly in the production of grassy crops (like corn). In lawns its overuse borders on the insane.

Opponents of 2,4 D would like to see it gone, in large part, because of its toxicity and potential to cause cancer. And, indeed, there are some studies that show that 2,4 D has the potential to cause cancer, though these findings are inconsistent and ultimately inconclusive. Additionally, in terms of 2,4 D’s LD50, it’s about 170 milligrams per pound that a person weighs – over two times LESS toxic than caffeine. I’m not going to bother figuring out how much 2,4 D would be in an average glass of 2,4 D because, well, I’ve never been served a cup of 2,4 D before and hopefully I never will. (If you’re curious as to how much 2,4 D would be in a cup of spray if you scooped it right out of the spray tank — then about 50 mg is a good estimate though it could be higher or lower depending on a lot of factors).

Anyway, this leads me to a ton of further questions, the most important of which is, without doubt, do anti-pesticide activists who fear the health dangers posed by 2,4 D drink coffee?

For those of you interested in these types of questions I encourage you to look over this article: http://www.marshall.org/article.php?id=73 It is posted on the website of a conservative group (which will probably alienate some of you and make others happy) – but it was originally published a number of years ago in a well respected journal and is one of my favorite articles ever in terms of getting the old brain thinking (Please don’t get the idea that I agree with everything in the article – I do not). Bruce Ames, one of the authors, is what we call in academia a “heavy hitter” and so, even if you don’t agree with what he says, his words are well worth reading.