The Garden Professors™ – Page 115 – Advancing the science of gardening and other stuff since 2009

Clematis mystery solved

Friday’s quiz was a tough one. Bernadette and Lisa B. gave it a good shot, guessing that this might be a phosphorus deficiency. While they’re on the right track (it is a nutritional disorder), the mineral of interest is iron, and it’s a toxicity problem, not a deficiency.

Under wet conditions (the affected Clematis is in the part of our landscape with a perched water table – see the March 15 posting), iron is predominantly in the Fe⁺² form (ferrous) rather than the Fe⁺³ form (ferric). The ferrous form is easily taken up by roots, and when leaves accumulate too much iron they turn reddish-brown. This diagnostic characteristic is called bronzing, and it’s different than the reddening caused by anthocyanin accumulation. (As an aside, nonagricultural landscapes rarely have phosphorus deficiencies and are more likely to contain excessive levels of phosphorus.)

Finally, all this talk of iron has reminded me of one of my favorite chemistry puzzles – see if you can figure out what this is:

Give up? It’s a ferrous wheel!

Friday quiz – a tale of two clematis

These two Clematis are the same cultivar growing in my landscape about 15 feet apart. Both are growing on a fence facing north. Compare the leaves of the two:

Normal, happy Clematis

Not-so-happy or -normal Clematis

What do you think is causing the leaf discoloration? Very large hint: this is not a biotic stressor. Another hint: you’ve seen this part of our landscape before…back in March. For full credit, identify both direct and indirect environmental stress (in other words, [1] what is directly causing the discoloration in the leaves, and what is allowing [1] to occur, thereby causing stress indirectly)?

Answers on Monday – have a happy 4th of July.!

An interesting blog for science-loving oenophiles

There’s a new blog already generating a lot of discussion among wine aficionados. The not-so-subtly named “Biodynamics is a hoax” discusses all things related to Rudolph Steiner and his philosophies, including the pseudoscience of biodynamics.

Organic farming study at – gasp! – a research university

There is a common misperception among some that university researchers are in the pocket of Big Ag (see June 11 and 13 posts). So here’s a link to an article in today’s Seattle Times about the benefits of organic farming from a study at Washington State University. The research was published in Nature (one of the most revered of the scientific journals).

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.

The Other Lamb’s Ears

I’m assuming even you tree people (aka other
Garden Professors) are familiar with the soft, silvery leaves of Stachys
byzantina or Lamb’s Ear (variously Lamb Ears and Lamb’s Ears). Not to
disparage S. byzantina, but in our part of the world it looks like a
pile of wet dryer lint in the winter; and can become similarly
disfigured during a hot, wet summer. Spring brings bright,
pet-able new ears, followed by woolly flower spikes that could serve as
Q-tips for Shrek. Runs/reseeds like a banshee in my home garden.
As
Dr. Allan Armitage notes, “We’ve been lamb-eared to death.”

But there are several other species of
garden-worthy Stachys, one of which is garnering lots of attention in
our campus garden at the moment. Behold, Stachys officinalis ‘Hummelo’ – Wood Betony or Alpine
Betony.

Also sold under S.
officinalis and S. densiflora. Most nurseries seemed to have settled on
S. monieri, but that specific epithet does not appear in the ITIS
(Integrated Taxonomic Information Systems) database. Armitage lists it as a cultivar
of S. officinalis and then has S. monieri as a separate species.

Regardless of pedigree, ‘Hummelo’ is a terrific perennial.
Clumps of glossy green scallop-edged foliage are topped with
spikes of rosy-lavender flowers throughout the summer. Heat- and
cold-tolerant; it’s hardy from Zones 4 to 8. Full sun or part shade,
drought tolerant, deer resistant…what’s not to like?

Back to the ubiquitous version of lamb’s ear…we
have a superior selection of S. byzantina with the fabulous cultivar
name of ‘Countess Helene von Stein’. Rarely flowers, and has bigger, tougher leaves that hang in there regardless of humidity. Very effective
when barked at students with a Teutonic accent: “Countess Helene von
Shtein! You vill learn dis plahnt!” You may find this in
the U.S. under the comparatively boring ‘Big Ears’.

Garden seminar coming to a place near you?

I just got back from British Columbia where I spoke to 2 garden club/Master Gardener groups. It’s always easy for me to do seminars in BC or along the west coast, but I rarely get a chance to go elsewhere. Many times it’s the expense that keeps groups, especially garden clubs and nonprofits, from bringing in speakers.

So here’s my idea: I keep a gift account budget here at WSU with the donations people make towards my educational program. Occasionaly I’ll make an equipment purchase, but for the most part it’s intact. And today it hit me – why not use it to help fund travel throughout the US (or elsewhere?) to give educational seminars?

So before I go any further with this thought, maybe some of you can give me feedback. Would your institution/garden club/or other group be interested in having me give a seminar on some aspect of sustainable urban horticulture? Just post a reply in the comments with your general location. I’ll see if there’s enough interest to pursue this further. I’d probably try to organize this trip for sometime in late February-early March of 2011.

Mystery berry revealed

You guys are just too smart – I was hoping to trap someone into guessing a Vaccinium species. But no, you all knew this was a Taxus spp. (yew):

Because Taxus is a gymnosperm, this reproductive structure is actually a cone. It’s botanically incorrect to call it a fruit of any sort, as the term "fruit" refers specifically to angiosperms. Taxus cones are modified for seed dispersal to include an edible, fleshy aril (very good, @GardenHoe!), whose taste and color are attractive to birds. The seed (which is toxic, like all vegetative parts of the plant – you’re right, Jimbo!) passes through the gut undigested.

The toxin in Taxus is the alkaloid taxine. Like many alkaloids, it’s a potent neurotoxin. Other alkaloids you’re more familiar with include caffeine, nicotine, and codeine.

What’s old is new again

While the Emerald Ash Borer (EAB) continues to expand in the upper Midwest (see http://www.emeraldashborer.info/files/MultiState_EABpos.pdf for a current infestation map), EAB is old news here in Michigan, especially in the southeastern part of the state. Efforts to restore urban and community forest canopy lost to EAB will continue, however, for the foreseeable future. In 2003 we established an Ash Alternative Arboretum MSU Tollgate Education Center in Novi, MI – which is near ‘Ground Zero’ for the EAB infestation in North America.

The planting offers some insights into selecting alternative landscape trees to replace ashes. A couple of elm cultivars, in particular, have emerged as shining stars in the demonstration planting that includes five specimens of 37 different species and varieties. All trees were planted as 1½”-2” bareroot liners by Tollgate volunteers. Tollgate farm manager Roy Prentice has overseen the maintenance of the planting.

Accolade elm (Ulmus japonica × wilsoniana ‘Morton’) Compared to most of the other selections planted in the arboretum at Tollgate, Accolade elm looks like a man among boys. Growth of these trees has been outstanding – the trunks of the trees have grown fast enough that they have split off their plastic rabbit guards (see photo). Like Triumph elm, Accolade elm has dark green glossy leaves and develops into a large tree. Although elms are often thought of ‘ugly ducklings’, both Triumph and Accolade are quickly developing well-formed vase-like crowns.

Triumph elm (Ulmus ‘Morton Glossy’) has also done very well at the Tollgate planting. This elm develops a vase-like crown with age and has dark green, glossy leaves. A large tree to 55’.

The elms are part of series of elm cultivars that have been developed with high tolerance of Dutch elm disease. Most of the new elms are hybrid crosses with Asian and European elm species, though selections of American elm that are tolerant of Dutch elm disease are also available in the nursery trade. The irony in all of this, of course, is that native American elms were devastated by another introduced exotic pest, Dutch elm disease. As elm trees were rapidly lost during the 1950’s, 60’s, and 70’s, ash trees became a popular replacement due to their ease of transplanting, growth rate, broad site tolerance and pest resistance (yet another irony). Now we’re promoting elms to replace ashes.

Street scene before and after Dutch Elm Disease. Photo: theprincetonelm.com

The moral of the Dutch Elm Disease and Emerald Ash Borer stories is that it’s critical to avoid over-reliance on one species or even one genus – even a native one. In Michigan some of our urban and community forests are over 50% maple. As global trade increases and the potential for destructive pests to hitch-hike around the world rises, the best hedge against catastrophic tree loss is to plant a broad and diverse array of adapted trees.

Friday mystery

I just got back from Nanaimo BC, where I had gooseberries with my afternoon tea. Below is another "berry" found on a commonly used ornamental. (I use the term berry loosely – as you may know, the botanical definintion for berry excludes fruits like strawberry and raspberry, which are aggregate fruits.)

I’ve photoshopped this so that only the two "berries" are visible. On Monday I’ll post the entire photo, along with some botanical fun facts! See if you can guess what this is before then.