Ecologists weigh in on native-exotic debate

Charlie Rohwer, a frequent guest contributor to the Garden Professors, brought to my attention a recent letter in Nature by Mark Davis and 18 other ecologist entitled, “Don’t judge species on their origins.” Davis is a leading authority on invasive species and author the book Invasion Biology. In their article, Davis and his co-authors make many of the same points that I’ve made here on the blog (Are natives the answer? Dec. 14, 2009; Restoration ecologists you need us – part 2. Aug. 9, 2010) regarding the native/exotic debate. The main point is that we need to develop a more pragmatic approach to managing landscape systems and this includes natives and exotic species; it’s not an either/or question anymore, not that it ever really was.

A couple of excerpts from their letter:

“It is time for scientists, land managers and policy-makers to ditch this preoccupation with the native–alien dichotomy and embrace more dynamic and pragmatic approaches to the conservation and management of species — approaches better suited to our fast-changing planet.”

“Clearly, natural-resource agencies and organizations should base their management plans on sound empirical evidence and not on unfounded claims of harm caused by non-natives. Another valuable step would be for scientists and professionals in conservation to convey to the public that many alien species are useful.”

The pragmatic approach that Davis and his co-authors (and I) advocate recognizes a several realities:

Exotics can fill many of the same ecological roles and niches as natives, Doug Talamy’s book notwithstanding.

Any inherent “ecological superiority” of natives over exotics has long since been negated by anthropogenic land-use change, alien pests, and climate change.

Attempts to eradicate alien species are largely warm-fuzzy exercises with little likelihood of success without liberal use of industrial-strength herbicides.

Gigantic hostas

I know Friday’s puzzle was a bit too easy – but I needed some way to discuss the giant hostas we have in our landscape this year:

We have had a very wet and cold spring.  While it was misery for us above-ground types, the plants absolutely loved the abundant water.  When the leaves open and expand on these continually-watered plants, they reach maximum size.  The hosta leaves in this photo aren’t the size of dinner plates – they’re more like turkey platters.

A word of caution to all of you with similar happy plants:  when the drier, hotter months of summer arrive, you’re going to have to keep these puppies well watered.  Otherwise, the leaves will soon turn crispy and brown around the edges.

One Of The Best Pictures I’ve Seen

Yesterday Jeff Hahn, an entomologist here at UMN (and author of the book Insects of the NorthWoods — a great field guide for Wisconsin and Minnesota), sent me a picture which reminded me of the dark ages and the methods that leaders of the past used to scare and intimidate their subjects as well as possible invaders.
 

This picture came to Jeff by way of Terry Straub, a Program Coordinator for Master Gardeners in Hennepin County.  Terry can’t remember where he got it from — The reason I’m mentioning this is that I’d love to give the person who originally took this picture credit for their brilliant (and somewhat disturbing) photo.

WOW again (Why oh Why?)

I’m going along with the “dead tree” theme of the week, but doing a little prognosticating at the same time.  Bert and Holly showed you tree demise on site; I’m going to show you tree demise in the making.  We can call this “dead plant walking.”

I’ve done a few WOW postings in the past, often with a focus at what you might find at a nursery or big box store.  Here’s a recent find at an unnamed BBS, in the “topiary” section:

Unless you intend to have a giant stake as part of your topiary statement, this tree (actually a juniper) will morph into a prostrate form before your very eyes. Fortunately, it probably won’t live long once transplanted since it’s so overdue for potting up that the pot has split:

You can just imagine the nest of woody roots fusing into a functionless mass, can’t you?

Run, don’t walk, away from nursery plants like this.  You’ll be glad you did.

Right Plant, Wrong Place?

It’s (apparently) Dead Tree week here on the GP!

[To my GP colleagues…we should make “Right Plant, Wrong Place” one of our categories, sort of like  “Knock it Off.” Or maybe just “Dead Plants in Action.”] 

Exhibit A:

Some unhappy little Magnolias. Drip irrigation was running, which leads me to believe salt spray is the culprit.

I was pedaling my sweet Electra beach cruiser down the sidewalk on Cape San Blas, Florida (or Cape San Blarrrgh, if you caught my post last week) and happened upon this tragedy.  In the background is natural coastal sand pine scrub including saw palmetto and myrtle oak. Growing on nothing but sand and a bit of decaying organic matter, 300 yards from the ocean, these are tough plants. Pretty darn salt tolerant.  Cabbage palms, also very salt tolerant, marched along the sidewalk. Southern magnolias had been planted in between, and they weren’t faring as well.

Just like “deer resistant,” “salt tolerant” is a rather vaguely-defined grouping of plants. You can find list after list on the interwebs and in the back of nursery catalogs and reference books.  The source of the information is rarely confirmed, and if so, it’s the same Extension publication that has been cut and pasted to death. Degrees of salt tolerance are further described as “high,” “moderate” and sometimes “low” without any quantitative parameters (a range of soil electrical conductivity perhaps?).  There are tremendous scientific resources (including funding) devoted to breeding for salt tolerance of food crops like rice, barley, and soybeans. Ornamental plants are pretty unimportant in the grand scheme of things (like the global food supply) thus the mere smattering of practically unfunded research out there, leaving us with only anecdotal evidence. Though some lists have M. grandiflora listed a “moderately” salt tolerant, I vote to move it to “low.”

Read and follow label directions…

Every extension specialist or educator that mentions any kind of pesticide in a talk or article always includes the disclaimer ‘Read and follow all label directions.” However that caveat ranks somewhere between “Your seat cushion may be used as a flotation device” and “Do not remove tag under penalty of law” as the most ignored phrase in the English language. While we can probably rationalize ignoring the last two (If a jetliner ditches in the middle of the Atlantic is a seat cushion really going to save you? And when was the last time you saw someone led away in handcuffs for pulling the tag off a mattress?); failing to pay attention to pesticide labels can have some real and immediate consequences.

 

I got called recently to inspect some tree and shrub damage at an industrial park in suburban Detroit.  (Because the case potentially involves some legal issues, I won’t mention names of any parties).  The industrial park included several hundred acres, much of it turf and landscape beds of trees and shrubs.  The park had its own groundskeeper but contracted out its spray applications.  A couple summer’s ago the staff groundskeeper complained several times to the contractor that they weren’t doing a sufficient job of keeping up with the weeds in the landscape beds.  The typical vegetation management tools of choice on this site were spot applications of Round-up (glyphosate) and hand-weeding.  For reasons that are not completely clear, this time the contract applicator reached for a jug of Sahara.    Even if you don’t know what Sahara is; what image does the name conjure up?  Parched. Barren. Lifeless.  Sahara is a combination of two herbicides (Diuron and Imazapyr) designed for complete vegetation control in non-cropland areas such as parking lots and rights of way.  And, unlike Round-up, Sahara provides foliar and root activity.  This is a product you use when you want complete burn-down and you don’t want anything growing there for a long time.

 


A hedge maple 2 years after herbicide application

Unfortunately, that was not the desired result in this location.  Within a week of the application, dozens of trees and shrubs all over the industrial park were either dead or wishing they were dead.  The smoking gun was not too hard to find.  The applicators had duly noted the herbicide application in their logbook and presence of active ingredient was confirmed in soil samples.  Although the parties are still working a settlement, the bids for replacing the affected trees and shrubs are well into six figures.

 


The unkindest cut of all.  These green ash were regularly treated with imidacloprid to protect against emerald ash borer.  An herbicide ap took them out instead.


Two years after application there are still bare zones where Sahara ran off from mulch rings and landscape beds.

Of course, all of this death and destruction (and legal wrangling) could have been avoided simply by…  Reading and following the label directions.  The Sahara label notes in several places that contact with roots can damage trees and other plants, including this explicit statement under a heading in all bold letters, PRECAUTIONS FOR AVOIDING INJURY TO NONTARGET PLANTS:  “Injury or loss or desirable trees may result if Sahara is applied on or near desirable trees or on areas where their roots extend.”  Sounds pretty clear to me folks – don’t use this stuff near plants unless you want them to die.

 

So, next time you or someone working for you has any question about what a pesticide does:  Read and follow label directions….

A jewel of an orchid

Orchid fanciers Derek and Joseph correctly identified Friday’s mystery plant as a jewel orchid, specifically Macodes petola:


Friday’s sparkly leaf photo shows why “jewel orchid” is the common name used for several genera of orchids with showstopping foliage.

And Ray noted that Goodyera spp. (rattlesnake plantain) is a native US jewel orchid with beautiful variegated foliage. Next time you’re hiking in the woods, keep your eye out for this common yet striking plant.