Amusing Facts – Page 7 – The Garden Professors™

Helium Makes Kudzu Float Away

As promised — some happy news: There’s this kid in Valdosta, GA (close to Tifton where I spent a few years as a graduate assistant), who has been experimenting with ways to kill kudzu. Here’s the video.

To see this kid work on something like this at such a young age is fantastic and gives me hope for the future. I wish the kid were here so he could come to the University of Minnesota – I think he has a lot to offer and he makes me slightly more optimistic about where horticulture ends up.

For those of you who choose not to view the video, what this kid does is to inject helium into the soil around the root system of a kudzu plant. After the injection the plant apparently dies. The exact reason why isn’t known, but one person who was interviewed said he suspected that the helium smothers the plants roots thus killing it.

I’m a little bit suspicious about that explanation, and I’m also a little bit skeptical about how much more economically feasible it would be to use the helium instead of more standard herbicides. I’m also very interested in any other gasses that he might have tried to kill the kudzu – I wonder, for example, if he tried propane? It might work, but I’d say it was too dangerous to try.

I’m suspicious about the helium smothering the root system of kudzu because kudzu has such an extensive root system and because the helium should dissipate pretty quickly, especially in sandy soils like they have in Southern Georgia. It’s also very unlikely that the helium itself is acting as a poison because helium is an inert gas. It just doesn’t react with anything. What I think is more likely is that, by finding the site where the kudzu’s stem enters the ground, this kid has found a “weak spot” on the kudzu which is susceptible to damage. Then I think that the helium acts a refrigerant when it is released and actually freezes the stem of the kudzu. However it works though, it’s a neat trick!

A Nice Museum

I’ve been to Chicago before, but mostly on business. It always seemed nice though, so, last week I went with my family and, for the first time, I had the chance to look at some of the sights. Navy Pier – overrated. Shedd aquarium – met expectations. Chicago style pizza from Giordanos – so much better than I expected. Chicago hotdogs – damn good, but not equal to Chicago pizza. The Field Museum – TERRIBLY UNDERRATED. I just loved the Field museum. There were all kinds of fantastic displays on everything from whales to evolution. There was also a great display on plants. The information in the display was spot on, but this was definitely one of the simpler displays at the museum. In fact, to be honest, it seemed a little bit like the display cases were made in the 1950s or 60s. That said, there was a lot of room for the display to spread out across, after all, this is, supposedly, a major attraction for the museum.

The thing is, no one was there. It was freaky. My wife was taking the kids to another display hall (one more suited to younger kids where they could actually play with stuff), and so I went to the plant display by myself. My feet echoed across the halls as I walked down the corridor. When I turned around to look at the direction from whence I came it felt like a movie where I was walking in a hallway from the fifties and everyone outside was hustling and bustling in the 21^st century. When I turned a corner in the hall there was a guy apparently passed out over his laptop. This was the only living person that I saw while visiting the display — and he obviously had no interest in plants – at least not when I saw him (Truth is, for all I know he was dead. The next day I felt guilty for not checking his pulse to make sure he was really alive). And, based on this photo from someone on flickr, I’m not the only one who has seen this exhibit empty.

Is this the interest that people have in plants today? How sad. No wonder we’re losing horticulture departments. But on a livelier note, I’ve been such a downer the last few posts that I promise I’ll provide something a little happier next week!

New Pot Crops

Just back from the national OFA Floriculture short course and trade show in Columbus, Ohio. There was quite a buzz (!) over the July cover story of the industry mag GrowerTalks:

Maybe, if there’s a variegated form…

GrowerTalks is NOT High Times. Commercial floriculture is a very, very conservative industry. Many family businesses. New petunia cultivars and seed-sowing technologies are the usual fodder for feature stories. But as a publication reaching out to people who grow plants under glass (or plastic) for a living, GrowerTalks has brought up a good point. As article author Jennifer Zurko points out, there are now 16 states where medical marijuana is legal, and many more have it under consideration. The average margin on wholesale bedding plant production is around 1.3. My guess is marijuana might do a little better than that. “Legal” sales in California are projected at $1.3 billion for this year. The entire U.S. Floriculture industry (wholesale value) is worth $4.3 billion currently.

Floriculturists are the preeminent controlled-environment specialists. Example: a grower takes an Easter Lily through 24 weeks of vernalization and bench production from bulb to buds, maintain a 2.6:1 plant:pot height ratio, and hits what is essentially a 5-day market window that changes yearly. Marijuana would be a comparative walk in the park.

Jennifer does a great job describing the caveats and issues, both technical and moral. Not least of which is that marijuana is, of course, illegal in the eyes of the federal government. But someone’s going to grow it. Heck, Scott’s Miracle Grow is already working on water-soluble fertilizer specific to the crop.

Hot weather and not-so-hot advice

Today I was sent a link to a posting on “droopy leaves.” Essentially, it suggests that droopy leaves are a means to conserve water on hot days and that watering these plants causes more problems than it solves because the roots don’t get enough oxygen. A link to the science of transpiration is provided. The advice is to wait until the evening and if the plants perk back up, then they didn’t need water after all.

This is one of those maddening articles that has enough science in it to make it sound reasonable, but is ultimately incorrect in its assumptions and advice. It’s worth looking at the topic in a little more detail.

Some plants are adept at conserving water in hot weather. Their leaves tend to be small, thick, with a heavy layer of waxes protecting the surface. Leaves can also move to limit their sun exposure and thus reduce the heat load. But wilting is not a method of conserving water. Instead, it’s a sign that water loss (evapotranspiration through the leaves) exceeds water uptake from the roots. And if you ignore wilt, you do so at your own peril. Once terminal wilt is reached, it’s all over for that part of the plant.

Wilt. Sorry it’s a fuzzy photo.

Large, thin leaves, common in many of ornamental, annual and vegetable species, do not conserve water. Tomatoes, zucchini and black-eyed susans, the plants specifically mentioned in this article, are not water conservers. Chronic wilting of these and other can eventually cause leaf tip and margin necrosis (or tissue death). It also reduces growth, so that your yield of tomatoes, zucchini and black-eyed susans will be decreased.

Leaf tip and marginal necrosis from chronic drought stress

So yes, do water your plants if they are wilting in the midday heat! Use mulches to conserve water! (You’ll notice in the photograph on the linked site that the plants are in bare soil.) Fine root systems are generally near the soil surface, and keeping these hydrated keeps them alive. You won’t see an instantaneous response to watering if plants are already wilting, but they will recover – much better than if you don’t water them at all.

Does colored glass help root cuttings?

I get a lot of questions about a lot of different products and practices. New topics send me to the scientific data bases and that’s where I went for today’s posting. One of my garden writing colleagues asked me about colored glass rooters – glass containers in different colors that can be filled with water and a plant cutting. The conventional internet wisdom, according to my colleague, is that green and blue glass rooters are the best.

The first mention I could find of such a practice is from an 1801 publication called The Cottage Gardener. In it, we’re informed that for rooting cuttings “such coloured glass is useless; it has no influence over the production of roots.” Nevertheless, 200 years later web postings like “I have found that cuttings placed in colored blue or green glass root faster than clear glass” are taken as solid evidence that blue or green glass containers are best for rooting cuttings.

There is science behind different colors of light and rooting, but it’s a little more complicated. Chlorophyll absorbs red and blue light best, so plants whose leaves are exposed to red and blue light grow well and tend to produce a healthy flush of roots. On the other hand, plants whose roots are exposed to blue light have decreased root growth compared to those under white light conditions. In this case, the photoreceptor called cryptochrome might be responsible for inhibition, as it is a blue light absorber. Similarly, plant roots exposed to green light do not grow as well as those exposed to white light.

In my opinion, this is another example of aesthetics trumping science. Of course colored glass rooters are more attractive that plain old glass jars. And that’s a perfectly valid reason to use them as part of one’s home decor. But it’s not science, nor is it necessarily the best way to encourage rooting.

What seems to be most important in rooting cuttings in water is to use indirect lighting (north-facing windows in the northern hemisphere, for example) so that the water doesn’t get too hot. And keep in mind that not all species root well from cuttings.

Getting Stung Can Be Fun!

Today I was reading a review of Amy Stewart’s new book Wicked Bugs and noticed the glee with which the reviewer noted that stings of various insects have been rated on a four point scale. Having read Amy’s book I can wholeheartedly recommend it, but in terms of the stings I thought, what the heck? Let’s see if I can impart some glee to our readers by taking a look at the pain that stings cause (I think it’s kind of like highbrow slap-stick). So here is a brief review of sting science over the years.

First of all, scientists have known for some time that the pain of an insect (or spider) sting is not necessarily correlated with the amount of damage which the sting causes, so scales that have been used to assess the pain of insect stings do not necessarily correlate with the amount of damage done by the sting. The stinging critter is not actually trying to kill the person which it stings (though stings may certainly kill smaller critters), rather, it’s trying to keep them away from itself and its family.

The first person in modern history to actually go to some trouble to figure out how badly a sting could hurt you was William Baerg who, from what I can tell, was dared by a colleague to get himself bitten by a black widow around 1923. He did so, but since the bite didn’t hurt too badly he had the spider bite him again the next day. After this second bite he recorded his reactions – including difficulty in breathing and talking. Apparently a masochist, Baerg continued to allow himself to be stung by scorpions, centipedes, and tarantulas — supposedly in the name of science. And here I’ve gotta say that, as a scientist, you need to set some limits. Actually the stings must not have affected Baerg too badly – he lived from 1885 to 1980.

Following in the footsteps of Dr Baerg, another scientist, Justin Schmidt, has been sting by a tremendous variety of venomous insects (I’ve heard that it’s over 100 different species) and has actually developed a scale to sort out which hurts the worst. The scale runs from 1-4 with a 4 being “debilitating” and 1 being a “spark”. Apparently he never gets stung on purpose – but dang, you can’t be trying too hard to avoid the stings if you’ve got that many species on your “been there done that” list.

Dr. Schmidt published his first paper on the painfulness of stings in the early 1980s. His work was soon followed by a paper published by Christopher Starr. The name of this paper was “A simple pain scale for field comparison of Hymenopteran stings”. This paper includes a list of insects and the level of pain which they cause with their sting – basically following Schmidt’s work – but Starr makes sure that he has at least two data points before he lists the pain which the insect causes. He also makes a point of noting when the insect was induced to sting instead of having the sting just happen. According to his chart he was stung by 34 (if I counted right) different insects, and of those stings only 6 were induced. Obviously this guy didn’t take his work as seriously as Baerg or Schmidt!

Most of the stings that we’re accustomed to – bees and wasps – are around a 2. There are a few at a level of 4 – probably the most notable is the bullet ant.

Starr ends the conclusion section of the article by listing 6 important rules for grading stings – I found them fascinating – so here they are:

Reports should only be made by adult observers in good health.
Disregard all stings accompanied by allergic reactions.
Reports should not come from observers who are rarely stung. This is to avoid mixing pain and novelty.
Reports should be based only on events in which a very small number of stings are received at once.
A ranking should never be based on just one sting. Although individual social wasps probably sting rarely (I suspect that most never do), so that significant day-to-day variation in venom volume is unlikely, uncompleted or grazing stings are uncommon. It is not known to what extent the regular use of the stinger by solitary wasps causes variation in venom delivery.
Reports on stings received through free attack by the insect (volunteer stings) are preferable to those deliberately induced by holding her between the fingers or against the skin (induced stings). We are not always so fortunate, though, to be attacked by those species of special interest……[deleted for brevity]

Exploding watermelons and exploding hysteria

One of our loyal blog readers passed on this interesting article about exploding watermelons in China. Seems that Chinese farmers have been overapplying a synthetic growth regulator which has led to the of proliferation of plump pepos (gotta love alliteration!). Of course the media has “blown” this out of proportion with action verbs like “explode” and “erupt”, when what’s actually happening is that the melons are merely splitting. (It’s a pretty boring video if you take time to watch it.)

Ok. This isn’t to defend the practice of misapplying any chemical. But the fear generated is obvious in the comments on this video – just scroll through them. The growth regulator in question is forchlorfenuron – a cytokinin legal in the United States and approved for use in very low concentrations on kiwifruit and grapes to enhance fruit size, fruit set, and cluster weight. It’s been approved for use in the US since 2004 and has been tested extensively prior to that approval for human and environmental safety.

Fruit split happens all the time during ripening. I’m sure most of you have seen this yourself, like when your tomatoes are overirrigated or cherries get unseasonal rain. And it can happen when growth regulators – natural or synthetic – are misapplied. But the fruit isn’t dangerous. It just looks bad, and might not taste that great, either.

There are lots of things to worry about out there. But growth regulators used in fruit production really aren’t one of them.

When Trees Don’t Know They’re Dead.

Last week a neighbor of mine called me up to ask how likely it was that their 4 year old (or so) crab apple tree was dead. Sometime over the course of the winter cute fuzzy bunnies had decided that the tree’s bark was tasty and decided to eat it. Naturally they ate it all the way around the circumference of the tree with the exception of a strip about an inch wide. At this point you’re probably asking yourself why the neighbors suspected the tree might be alive. The reason they were calling me was that the tree was leafing out– so they figured that maybe the tree would make it — that maybe, just maybe, it wasn’t as bad as it looked. My answer — Sorry, the tree is dead, it just doesn’t know it yet. As a rule of thumb you can have up to a third of the circumference of a young tree girdled and the tree has a decent chance of growing out of it. More than that and, though the tree might live for a few years, you’re dealing with so much damage to the vascular tissue that you’re just putting off the inevitable by not cutting it down. A tree with as much damage as my neighbors tree had was just going through the motions.

When bark is eaten what is destroyed is the phloem — the tissue which carries the carbohydrates made by the leaves down the plant’s stem. The cambium — which creates new phloem and xylem — is also destroyed. But the xylem — the innermost tissue which transports water and nutrients up the stem — is left largely intact. So girdled trees will flush out in the spring (using resources provided by the xylem), perhaps even two springs, but ultimately the tree will succumb.

But there is an up-side! Girdled trees will be under a lot of stress. Stressed trees tend to flower heavily — so enjoy the show first, then cut down the tree.

A word about GMOs from our visiting GP

I gave a talk to a group of gardeners last year about vegetable and community gardening. There was a wide variety of gardening experience represented, but one statement from a seasoned gardener bothered me a bit. And I think my response bothered him a bit too. I haven’t thought much about it until recently, when a high school English teacher I know told me a student expressed similar ideas in her class. The erroneous idea from my audience member was this: our tomatoes are being poisoned with ‘germetically modinified’…something something. The arguments have lost me beyond that (because there aren’t any). And really, there hasn’t been much talk about sex on this blog recently, so that should be remedied too. Therefore, I would like to take the platform offered by the Garden Professors to talk about plant breeding.

Fig. 1: Jaune flammee, which has at least one gene from at least one of its parents that causes the fruit to have very little lycopene.

Conventional” breeding is when a plant breeder selects parents and offspring and tests them for desirable characteristics (traits). It works the same way as breeding works in nature, except that we humans have a goal we’re working toward. Firm, 5-oz, disease-resistant, crack-resistant tomatoes, for example. In nature, the offspring that survive and reproduce the best in a given environment are ‘blindly’ selected and tend to stick around (Darwin, 1859). Male (sperm) cells are transferred to female (egg) cells by a plant breeder, or a bee, or the wind, or a beetle, or a fly or bird or bat or moth (etc.). The sperm and egg fuse to form an embryo, which grows to become what we’d call a plant. In both natural and artificial selection of tomatoes, no non-tomato DNA has been added, and no tomato DNA has been removed. By the classical definition of ‘genetic modification’, there has been none. I suppose this paragraph was only incidentally about sex, and probably a disappointment to some. Sorry.

Fig. 2. Tainan, a tiny heirloom

The confusion of the issue may lie with the Flavr Savr tomato. This was developed (yes, genetically modified) in the mid-90’s to resist softening during ripening. It has a couple bits of manufactured DNA in it to make this possible. The Flavr Savr is no longer grown or sold in the marketplace (that was SO 1990’s), and to my knowledge, no other transgenic tomatoes are either.

Fig. 3. Rutgers, historically much-cultivated and like all other tomatoes we can buy, bred conventionally.

Confusion may also lie with the plant hormone ethylene. Ethylene is made from incomplete combustion of fossil fuels, but it’s also made by plants. Keep your bananas away from your carnations, right? Bananas make ethylene gas, which causes carnations and snapdragons to senesce (die). Tomatoes make ethylene as they ripen. If you harvest tomatoes a bit early, but not too early, they are hard enough to ship but will still turn red later. If you expose these pre-ripened tomatoes to ethylene gas, they will ripen more quickly and uniformly. That’s what happens to a lot of the tomatoes in our stores. They are not genetically modified, they are treated with a plant hormone. That’s not unusual at all. Ethylene is used to ripen bananas, and to help make cucumber seeds (by eliminating male flowers from female parents). It’s used in growing ornamental plants quite a bit too (but not as much as many other hormones, and especially hormone inhibitors).

So please, if you are someone who tells anybody who will listen that the tomatoes in the store are GMOs, stop it. They’re not.

I’d be happy to answer any questions you might have…

Patience: A minor form of despair, disguised as a virtue.
– Ambrose Bierce

We just completed our annual student/hort garden spring plant sale. I spent the better part of three days encouraging, suggesting, wheeling, dealing, and dispersing information, most of it sound, and all for a good cause. Generally enjoyed my legitimate excuse to sell some plants and also stay away from my ridiculous desk/computer. My “Ornamental Plant Production and Marketing” seniors have a unique interest, as they not only grow plants for the sale, the last bit of the semester has been spent discussing cost accounting and (much more fun) marketing, including garden center management. Through the hort club sale, they get to deal with real people with real questions.

One of these real people accosted one of my students late in the day Friday. Off in the distance, I saw an animated exchange as he nervously pointed her in my direction (ask Dr. Holly!)

“Is this a cultivar?” the rather intense lady barked (yipped, actually) as she marched over and shoved a quart pot of Allegheny spurge (Pachysandra procumbens) up to my face. Close enough that I could read the big ol’ label quite clearly – which did not list a cultivar name.

“Doesn’t seem to be,” I deduced, rather brilliantly. Did I mention it’s perilously close to beer:30.

I processed for another moment, and then noted “I don’t think I’ve ever seen a named selection of this.”

“Are you sure?! Because I don’t want any cultivars, you know, things that have been MESSED WITH!”

Here we go.

“Ma’am, many of our perennial and woody plant cultivars are simply selections identified by some eagle-eyed and knowledgeable plantsperson as perhaps more compact, or more floriferous, more vigorous, maybe a different color, etc. Nature, in many cases, has already done the work.” Working under a suspicious glare, I go on that plenty of named cultivars are virtually indistinguishable from the straight species or botanical variety; for better or worse; it’s mostly just a marketing thing. Echinacea purpurea var. alba just doesn’t sing like Echinacea ‘White Swan’. Though there are (obviously) plant breeders out there working to create new/superior/weird stuff (usually patented), but really, the historical bulk of what we have in our gardens is the stuff of perspicacious serendipity.

Said species, courtesy of NPIN.

She pursed her lips, stared hard at the tag, and repeated “But how do I know this hasn’t been MESSED WITH? And when it says native – that means to here, right?”

*Pop* goes yet another can of worms.

I guess I could have said “Yep.” Pachysandra procumbens appears on everyone’s “native groundcovers” list east of the Mississippi. However, it is not native to Southwest Virginia, despite our location on the eastern edge of the Alleghany Mountains. It’s fairly rare, mostly found in the Cumberland Plateau of Tennessee and assorted limestone-y bits of Georgia, Alabama, and Kentucky. I take a deep breath and commence with the disclaimers.

I thought I was doing pretty well; then behind me I hear a familiar voice – Dr. Stephen Sheckler, lauded botany professor emeritus, poobah in the Linnaean society, and loyal plant sale shopper. He stepped in with an “I couldn’t help but overhear” and proceeded to explain the effects of glacial episodes on native flora distribution a mere twenty thousand years ago and Pachysandra may have indeed been native here if you look at the broader picture etc. etc. etc. Five minutes later, he was explaining why we have similar ecotypes to the Yunnan Provence, and I excused myself and wandered off to sell a Japanese maple. We’d both tried to answer her questions to the best of our ability. My utmost respect and admiration goes out to those of you in retail who do this on a daily basis.

My student was pleased to reported that she went back and bought the entire tray.