Knock It Off – Page 11 – The Garden Professors™

Tips for garden writers from a science writer

Much as I am itching to continue the current discussion on cultivars of native plants, I’ve got to wait until next week (my seminar schedule has me hammered – doing my third one this week tomorrow). So instead I thought I’d throw out some suggestions for those nonscientists who blog and/or write about all things planted.

First of all, I do enjoy reading blogs, articles and books by nonscientists who venture into plant and soil sciences. But there are common errors that both interrupt the flow and – fairly or unfairly – can cause me to question the writer’s grasp of the subject matter. Here are some of them in no particular order:

Nomenclature:

1) Common names are not capitalized unless they contain a proper noun. (This is a general taxonomic rule for plants – and sorry, I didn’t write the rules!)

2) Scientific names are always italicized or underlined; the first letter of the genus is capitalized, the species name is usually not. (Also, they’re not “Latin names” – many scientific names actually come from Greek roots.)

3) While we’re on scientific names and in a nod to our discussion of cultivars, let’s address that one too. When a scientific name is followed by a cultivar name, the cultivar name is either preceded by cv., or is set off in single quotes. The cultivar name is capitalized. So this is how the weeping blue atlas cedar would appear: Cedrus atlantica ‘Glauca Pendula’ or Cedrus atlantica cv. Glauca Pendula.

4) Plant family names always end in -aceae, which literally means “family.” When someone writes “the Asteraceae family” they are being redundant. (This always reminds me of a scene from Mickey Blue Eyes, where the characters are discussing a restaurant called “The La Trattoria” – which, of course, translates to “the the restaurant.”)

Scientific information:

1) The word “data” is a plural noun (datum is the singular form). Therefore, “data” must take plural verbs.

2) “Proving” that a product or practice works. The philosophy behind the scientific method states that one can never definitively “prove” anything. Thus, we can have results that support a hypothesis, or we can disprove it. (Yes, marketers do this, but garden writers shouldn’t.)

Terminology:

1) “Pesticide” is a generic word that means “pest killer”. Herbicides kill plants, fungicides kill fungi, and so on. Many nonscientists incorrectly think that pesticide means the same thing as insecticide. It does not.

2) Flowers and fruits are reproductive structures of angiosperms (the flowering plants). Conifers do not have flowers, nor do they have fruits; their seeds are born on cones. Many scientists, as well as nonscientists, incorrectly label the cones of Ginkgo and Taxus (yew) as fruits.

I’m sure my GP colleagues can come up with some other ones, and maybe you can as well. Comment away!

W.O.W. (aka Why oh why do nurseries sell this plant)?

Since we’re back on the alien train (spaceship?), I thought I’d bring up another of my least favorite shrubs – Scots broom – as our next installation of WOW (why oh why?).

Scots (or scotch) broom (Cytisus scoparius) is a much-reviled intruder in the western and eastern United States. Originally introduced as a sturdy ornamental, this legume quickly invaded disturbed areas and is labeled as a noxious weed in several western states. In Washington, it’s quarantined. Research dollars have been dedicated to studying best methods of eradication. So it doesn’t take a rocket scientist (or even a garden professor) to figure out that it’s probably not a wise addition to one’s landscape.

But apparently some nurseries either (1) haven’t paid attention or (2) don’t care. In a quick look at the internet, I found nurseries in many states, including Oregon and California, that sell this species. Many will argue that they are selling “less invasive” or “sterile” cultivars, which is a poor excuse in my opinion. Readers of this blog know by now that cultivars often revert to wild type, and there’s no reason to assume that broom cultivars are exempt from this ability. Furthermore, we know that plants have the ability to extend their ranges past what we think they are (hello kudzu?).

Just popping in to say hello

There are many ornamental alternatives to Scots broom that can easily be found online or in print. I’d love to hear some rational arguments from nursery owners, landscape designers, or anyone else justifying the sale of this plant.

My Long Suffering Basil

Sometimes I am not such a good garden professor. That’s because, when I get home, I sometimes (OK — often) don’t give my plants the attention they need. It’s also because, when we leave for vacation, I often forget to tell whoever is watching the animals to keep their eyes on the plants too. Now, really, you would think that someone who saw a plant on the back porch in full wilt would think “Hey, Maybe I should water that!” But still, I blame myself for not spelling it out.

What this all leads to, of course, is that we had a group of really nice basil plants in a container on the back porch which weren’t watered for a week while we were on vacation. There was little rain over this week, and subsequently the basil was in full wilt for at least 2 days (perhaps as long as three). We watered these plants soon after we arrived home (my wife loves caprese salad) and the plants perked up a bit, but the leaves were obviously damaged and now our salads will be a little less flat.

It’s not just basil that is affected by an incidence of drought. Most plants, including trees, will actually suffer for a considerable period of time after the event. Sometimes growth won’t return to normal for as much as a year or two. This is a really bad situation if you’re buying trees grown in containers. If the grower, or retailer, didn’t know what they were doing and let the tree wilt severely prior to selling it to you then buyer beware!

Why won’t landscapers use mulch?

A few weeks ago I was in Olympia (it misses you Bert!) reviewing grant applications. As I tend to do whenever I have time and my camera, I set out in search of gardening goofs that evening. Here’s the edge of a relatively new commercial site I discovered:

OK, not too bad so far. We’ve got a nice stone mulch next to the curb, then a lovely groundcover, in flower, that also functions as a living mulch. But what’s that we see in the upper half of the photo?

Yes, it’s Canada thistle (Cirsium arvense), an aggressive perennial weed that spreads by stolons and can make dense monocultures of prickly nastiness. In fact, the front is already advancing on our little groundcover:

Had the landscapers continued with mulching the soil rather than leaving it bare, these thistle seeds might not have germinated. But for whatever reason, the bulk of the landscape was left bare:

I’m sorry, but this just looks ridiculous. There was some obvious care in laying the stone mulch and groundcover, but then the landscaper seems to have run out of time and/or money and just plopped in some bulbs and corms. It reminds me of a birthday cake.

I don’t understand the rationale behind this. Was this a real design? Did the client run out of money? Or (as the more cynical side of me wonders) was this done deliberately to create a high maintenance landscape requiring lots of weeding in the future?

Thoughts?

Why bother having trees?

Sorry to be late with my post this week – I was away reviewing grant proposals. It was interesting and useful work, but really drains your brain. So with that being said, my post is long on pictures and short on words.

One of the things that bugs us GP types is poor plant placement. Why bother planting a tree if you’re not going to allow it to grow naturally? Here are some photos to mull over the weekend. While I have lots of bad pruning pictures, these ones are chosen specifically because the trees were obviously poor choices for either site usage or size.

Because my sense of humor seems to have been left at the grant reviewing venue, I can’t think of amusing captions for these pictures. But I’ll bet you can! Just submit them in the comments sections, and I’ll repost the photos later next week with your contributions.

Photo #1

Photo #2

Photo #3

Photo #4

Photo #5

GP Hit List: Ligustrum sinense (Chinese Privet)

[And I don’t mean “greatest hits”, I mean “Mafia hit”]

Gardeners, yardeners, and designers are on a perpetual lookout for a good hedge species. Hedges are useful in so many ways: providing backdrop for a border, making good neighbors, containing football players, etc. In reference to the latter, the field at Sanford Stadium at the University of Georgia (cue woofing!) is known as “Between the Hedges”. In the extensive lore of UGA football, everyone makes like it’s some sacred plant, but (gasp!) it’s just plain ol’ privet. Aside to Jeff, my fellow UGA alum: CNN just reported the dubious distinction that Georgia is the #1 party school in the country (again). Maybe this is why I can’t remember the Krebs Cycle.

Variegated Chinese Privet in all its shrubby glory; photo from University of Arkansas Cooperative Extension.

Back to privet. Designers of D.O.T. landscapes such as medians and interchanges seem especially enamored. Clouds of variegated privet (L. sinense ‘Variegatum’) dot interstates throughout the South. Yes, it’s tough, useful, variegated, and touted as “wildlife friendly” by some leading gardening resources. The berries are indeed good bird food; therein lies the problem. Seeds pooped out by birds results in the green, non-variegated version – much more vigorous and deposited everywhere. For the record, the variegated form also reverts like crazy.

My family’s farm in northeast Georgia is bordered by the North Fork of the Broad River. Over the years, the river bottom, and then the fence lines at all elevations, have filled with privet. It is, pardon my language, a total bitch to remove and almost impossible to eradicate. The State Botanical Garden of Georgia in Athens has an entire squad dedicated to eliminating it from acres of river bottom; ironically, only a few miles from Sanford Stadium. Thought of mostly as a Zone 7-9 plant; we have lots of it in the woods here in the mountains – an entire zone cooler.

Distribution of L. sinense; USDA PLANTS Database http://plants.usda.gov/

Ligustrum sinense is on at least two official Invasive and Noxious Weeds lists by the Southeast Exotic Pest Plant Council and Florida Exotic Pest Plant Council as well as several international lists. Nursery growers and landscapers across the South know these things. So why, why, why, do they continue to produce and spec it? “Variegated foliage sells. People see it, like it, and then ask for it. It’s a bread-and-butter item.” This comment came from the owner of a fairly large nursery that sells to independent garden centers.

Our industry yelps whenever a state or federal mandate threatens to impose restrictions on a best-seller (Hedera helix, for recent example). There are LOTS of terrific woody plants out there, people. The Dirr book is now up to 1250 pages – thumb through and pick a few alternatives. Cease and desist with the Chinese privet.

Where to draw the line on a vine

Last week’s column on “why do nurseries sell this plant?” struck a chord with many readers as well as with Holly! So here is this week’s submission: that ubiquitous vine, English ivy.

First of all, we’ll stipulate than many ivies are sold as English ivy (Hedera helix) but may be entirely different species. Genetic research on invasive ivy populations in the Pacific Northwest identify most as H. hibernica (aka Atlantic ivy), with H. helix making up only 15% of the invading populations. Regardless of their species identity, it’s obvious that Hedera is a genus with the potential to escape gardens and invade remnant forests or other environmentally sensitive areas. It grows so vigorously that it can create monocultural mats on forest floors; it grows into trees where its sheer weight can break limbs and in some cases topple entire trees.

But what about other regions of the country – or the world, for that matter? In colder climates, Hedera spp. are much better behaved, dying back to the ground every winter and rarely able to flower and reproduce. The absence of a seed bank means the vine can be kept in check more easily. And it does tolerate tough environmental conditions where other groundcovers might not succeed.

Yet consider another invasive: kudzu (Pueraria montana var. lobata) For decades this noxious weed was thought to be too cold sensitive to expand past the American Southeast. Yet populations have been found in Maine, Oregon, and most recently in Ontario, Canada. Plants adapt!

So – is it worth the risk to buy a plant known to be invasive elsewhere, simply because it’s not a problem yet?

And why oh why do nurseries in Washington state continue to sell Hedera spp. as ornamentals?

Why do nurseries sell this plant?

I wish I were more like Holly…wandering around nurseries finding pretty and unusual annuals and perennials to get excited about. Instead, I seem to gravitate to plants that annoy me.

Today while looking for some trellises (for those containerized Clematis vines that I’ve been torturing) I saw pots of the Equisetum hyemale (“a tall, evergreen, spreading, reed-like grass”) for sale:

As readers of this blog surely know, Equisetum spp. – or horsetails – are not grasses but primitive relatives of ferns. That taxonomic blunder aside, the thought of deliberately planting any Equisetum species in a landscape sends shivers down my spine.

Now E. hyemale is not as weedy as E. arvense, but in nearly every seminar I give on controlling weeds with mulch someone asks about getting rid of horsetails. Short answer – you pull. And pull and pull. There’s no good herbicide for them, nothing seems to eat them, and they spread aggressively.

And speaking of eating, did you know that horsetails are poisonous? They contain an enzyme (thiaminase) that deactivates thiamin (vitamin B1) in the unfortunate consumer’s body. The most common victims of horsetail poisoning, ironically, are horses. Horsetails are considered noxious weeds in pastures used for grazing – and yes, they are native to the United States.

Sure, horsetails are interesting looking plants. But do you really want something in your garden that the production nursery describes as having “indefinite spread?” And how does keeping them in a pot, as one production nursery recommends, keep them from spreading spores? Especially if you plant them “in or around ponds and streams?”

I just think this is such a bad idea for home landscapes. Even if it is a native species.

When criticism becomes libelous

Dr. Cregg is on vacation for a few weeks so I thought I’d post something today by trolling the web for discussion of my horticultural myth columns. And when you go fishing, you know you might catch something you didn’t really want. In this case, personal and professional attacks.

Like the rest of the GPs, I relish vigorous debates on different horticultural practices and products. Ideally, these debates are based on science, so that we’re all friends afterwards and could go out for beer if we all lived in the same community. But when criticisms become personal, malicious, and in some cases out-and-out untruths, what should one do?

I have a relatively thick skin and ignore most of the nasty comments, but when my integrity as a scientist is challenged, I really have a problem. For instance, one blogger states “The fact that some – not all – of her articles have very little basis in reality and are widely disputed and even denounced in horticultural circles should be pointed out before anyone takes them immediately to heart.” Another blogger remarks “What little I’ve read about this Chalker-Smith person leads me to believe she is an “opinion for hire” much like some “expert witnesses” one sees in courtrooms.” How about this? “She tried to prove compost tea is bad by PURPOSELY using E.Coli infested compost (without telling anyone about it) and proclaimed it as unsafe product to use.” And so on.

I can guarantee you that if I didn’t base my publications in reality, or if I were an “opinion for hire” I would be in serious trouble with the university. The truth is I research the science behind topics and then have at least one colleague review them. (Sometimes that colleague is my husband, also a PhD in horticulture and one of my most honest critics.) The compost tea diatribe is so outlandish it took my breath away.

So onto my question: what should one do when one’s professional reputation is libeled? Do I continue to ignore it? Do I wade into these debates, thus giving credibility to the libeller? These people hide behind their anonymity – none have the courage to simply email me and voice their criticisms.

I’ll be curious to hear from my GP collaborators as well as non-academics.

(Hurry back, Bert. This was a painful experience.)

Cornmeal myth busted

As my colleague Fred Hoffman says, the horticultural silly season is upon us. This week I heard from one of our European readers, questioning the use of cornmeal as a fungicide. He referenced an online article entitled “Cornmeal has powerful fungicidal properties in the garden.” He hadn’t been able to find any reliable information and thought it might make a good topic for our blog. So Johannes, this rant’s for you!

If you’ve followed the link to column in question, you’ll see that the original “research” is attributed to one of Texas A&M’s research stations in Stephenville, TX. But it’s not really research – it’s just an observation on what happens when you don’t plant the same crop two years in a row; in this case, rotating corn and peanuts reduces peanut pathogens. This is hardly news – it’s one of the reasons agricultural scientists recommend crop rotation as part of an IPM program. And have for decades.

Then we’re referred to “further research” (at an undisclosed location) where cornmeal was shown to contain “beneficial organisms.” Well, no, cornmeal doesn’t contain organisms, beneficial or otherwise. Microbes can grow on cornmeal, and in fact cornmeal agar is commonly used in labs as a growth medium for many species of fungi. And has been for decades.

Nevertheless, we’re informed that a gardening personality has “continued the study and finds cornmeal effective on most everything from turf grass to black spot on roses.” This is directly refuted by Dr. Jerry Parsons, who by happy coincidence is an extension faculty specialist at Texas A&M. His informative (and hilarious) column on brown spots in lawns states “Lately there have been claims made that corn meal and a garlic extract is effective. This is absolutely false! Everyone trying to do the “environmentally friendly-to-a-fault” thing have been wasting their money. They would have been better off making corn bread and using their garlic for cooking purposes!”

Dr. Parsons continues: “Let me explain how these University tests and recommendations have been misrepresented in a desperate attempt to find an organic fungicide. The corn meal was investigated by a Texas A&M pathologist as a way to produce parasitic fungi used to control a fungus which occurs on peanuts.” (This directly relates to my earlier point that cornmeal agar has a long history of use in fungal culture.)

It boils down to this: if you have a healthy soil, it will probably contain diverse populations of beneficial microbes, including those that control pathogenic fungi. You don’t need to add cornmeal – it’s simply an expensive form of organic material. So you can ignore the directions in the article on how to incorporate cornmeal into the soil, or make “cornmeal juice” to spray on “susceptible plants.” Just nurture your soil with (repeat after me) a thick layer of coarse organic mulch.

(As a footnote, let me say how annoying it is when gardening personalities grant themselves advanced degrees or certifications in their titles. C’mon folks – if your information is so great, do you really need to pretend you’re someone else?)

(Another footnote: I discussed this myth more in 2012. Be sure to check this link out too.)

UPDATE: Since this is a myth that refuses to die, I’ve published a peer-reviewed fact sheet on the topic. Feel free to pass on to others.