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
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.
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

Also sold under S.
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  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:

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.

Shear lunacy

I subscribe to Digger magazine, the industry publication from Oregon Association of Nurserymen.  I am always curious about trends in the nursery industry and this magazine is a good way to find out what home gardeners are buying.

The cover feature of the May 2010 issue is on topiary. While I can appreciate topiaries in formal gardens – with dozens of gardeners to keep them shaped up – I think they are poor choices for most home landscapes.  Shearing plants to maintain a particular size or shape is a never-ending activity that most homeowners will tire of quickly.  Nevertheless, the magazine reports that topiaries are becoming more popular for home landscapes, especially along the East Coast. The article showcases the newer topiary shapes – stars, crosses, angels, even cacti – in addition to the traditional spirals and poms.

The article warns growers that skilled employees are needed to prune topiaries properly, and that the time commitment to create and maintain topiaries is significant.  One grower states “it’ll take a fair amount of time to shape it, and then you’ll be trimming it lightly a couple of times a year until you sell it.”

Curiously, the article says nothing about either the time commitment or pruning skills needed for homeowners who purchase topiaries.

Even more curious…the subsequent issue of Digger is devoted to sustainability. Seems a bit of a disconnect there.



Visiting Virginia

The first thing that I did, gardening wise, when I moved to Minnesota from Georgia was to try all of the plants that I had grown to love in the South in the North — hoping beyond hope that perhaps someone had made a mistake when listing the hardiness zones of these plants.  The result was a mess of dead lacebark elms, Japanese maples, and butterfly bushes.  One plant that I did find could live, albeit just barely, was the beautyberry — a purple fruiting shrub that would survive as a perennial in Minnesota, just barely getting up to my knee — just enough to tease me.

Today I’m giving a few talks in Blacksburg VA and visiting fellow GP Holly Scoggins.  She runs the Hahn gardens here and has some truly beautiful specimens of many plants that I covet, beautyberry among them.  I am so jealous of people who live in the South and can grow this stuff to its full potential!

In this photo I share a beer with a large, lush beautyberry.  I think it might have been more impressed by a higher caliber beer. 

Creative Uses For Old Water Breakers

Why, oh why, can’t someone engineer a sturdy, long-lasting, horticulturally-correct water breaker.

We have, at last count, six hoses in use at our very spread-out garden & farm.  I go through a lot of breakers, and am down to two, which I rotate around.  In dire need of some new ones (as well as a huge bale of TP), I perused the garden aisle at our local big box (rhymes with “Target”).  Pistol grip schnozzles abound – these things that propel the water
like a 95 mph fastball.  Just what your plants want. Some had the “dial” for various water flow patterns, but these are never satisfactory.  Not a single real water breaker for plants among the 20 choices. So I shall do mail-order from FarmTek.

Dramm seems to makes the only functional water breaker, but alas, most of what’s in my busted-breaker-bucket are old Dramm heads (at $10-$12 a pop). Their commercial line is a bit better than the consumer items, where a rainbow of colors seems to be more important than structural integrity.  Anyone who’s worked in a commercial greenhouse has used their aluminum models or the plastic RedHead soft flow breaker, The only solid brass item in their line is the super-fine Fog-it Nozzle… I’ve had the same one since 1996.

A solid brass version of the full-size breaker would be great.  The point of failure (always) is the interface between the screen plate and the body/shell.  I hate replacing things. I’d pay for quality.

Hammer Time!
Obsoive.  My ingenious partner uses a water breaker body to keep bamboo from splitting (further) when pounded.  Principle of transference of impact from smaller area to larger surface, etc.  Tomato stakes finally installed!

Mystery photo uncurled!

There were a few brave souls who ventured to ID the mystery plant – a trunk shot is not particularly helpful, I know.  But I was hoping that its contorted nature might help a little.  (It wouldn’t have helped me at all, but you all know by now that I am NOT a taxonomist.)

So our mystery tree is a curly willow (Salix matsudana):

…which may or may not be synonymous with Salix babylonica.

In any case, it’s an interesting tree that’s relatively cold hardy.  Like many willows, it has weak wood and is prone to breakage.  But in the right location (away from targets) it could be a lovely specimen.