Some Interesting Projects and Fun Experiments

Research doesn’t stop just because someone publishes a book!  Since publishing my books I’ve conducted quite a bit of new research along with my co-researchers Gary Johnson, Chad Giblin, Dave Hansen, Bob Blanchette and others.  Below are some of our more interesting findings.  Besides the findings below, you can also find some of our work online at

Milk for Black Spot

Everyone loves the idea of using milk to control blackspot on roses, and it’s no wonder!  There are some nasty chemicals out there.  When we tested milk against other home remedies it beat everything else easily.  In fact, it was just about as good as the synthetic fungicide Chlorotalonil and the organic fungicide Bordeaux mix.  The recipe for using milk is very simple.  Just mix one part milk (any type of milk will do — except maybe chocolate) with two parts water and spray that mixture on your roses once a week.  Besides working on blackspot, other researchers have shown that there’s a good chance this spray may work on other diseases too.

Here are some roses treated with milk.  This picture was taken in the fall.  As you can see, they look pretty good without too much leaf loss.

Here’s what roses treated with another common household cure, Cornell mix, look like in the fall.  All of this leaf loss is due to blackspot.  Cornell mix is basically just a mix of baking soda and some soap and oil.

Cutting Apart Pot Bound Root Balls when you Plant

The current state-of-the-art in planting trees and perennials dictates that, if there are any circling roots on a plant that is being transplanted from a container to the ground, you should cut these circling roots.  Our research, however, is showing that cutting these roots may be a waste of time.  In our research on lindens and willows, cutting these roots actually decreased the number of roots emerging from the root ball.  This year we will be harvesting trees of a variety of different species that have been planted with and without rootpruning and then grown for four seasons.  When we take a look at their root systems we’ll have a much better idea about how effective this rootpruning is at encouraging new roots.

In the picture on the far left, you can see what some of the rootballs of the trees that we planted looked like.  In the picture next to it you can see that, even though the plant was potbound, the leaves came out normally, and all of these trees are doing just fine now.

Besides using normal root cutting techniques such as butterflying and slicing we decided to use some really drastic measures.  As you can see in the image on the far left, we actually cut some of the root systems into box shapes.  As you can see in the image next to it, that aggressive rootpruning really stunted the leaves of some trees — at least for the first year after planting.  All of these trees are doing fine now, too.

Slug Barriers

I love to test slug barriers; it’s just plain fun.  What I do to test these barriers is to take a plate, surround it with whatever barrier I’m in the mood to test, set a few slugs in the middle, and let ’em run.  If they cross the barrier pretty quickly, well, then that barrier doesn’t work.  If they take a long time to cross it, or die before they cross it, then it’s a good barrier.  I must admit, if you like slugs, this might seem to be a somewhat cruel experiment and so you may want to avert your eyes from the following pictures.  Besides slug barriers there are all kinds of other ways to control slugs like beer traps and iron phosphate.  Avoid metaldehyde, it’s both attractive and dangerous to dogs.

Everybody seems to think that slugs won’t crawl over eggshells.  Wrong!  They really don’t care about eggshells.  Diatomaceous earth, on the other hand, works great. I should add that some people do have luck with egg shells — that luck usually correlates with the presence of an unprotected alternate food source.  In other words, if there’s a hosta nearby that isn’t surrounded with egg shells, then egg shell protection may work for those plants that are surrounded.

So, used coffee grounds ought to stop slugs, right?  Well, maybe, but not in our experiments.

Ashes don’t work very well as a slug barrier either….at least not moist ashes.  I had someone tell me once that dry ashes work great….but I haven’t yet figured out how to keep these ashes dry in a rainstorm….

So copper is supposed to stop slugs cold, right?  Well, not according to our tests.  It’s true that the slugs didn’t seem to enjoy going over the copper pennies, but it didn’t exactly stop them either.

Not only will slugs not cross chewing tobacco, it will kill them.  All of these slugs are dead.  I don’t think tobacco is a great choice as a slug barrier though because it may carry plant diseases and because dogs may decide that they like the flavor — and then will wait until they’re inside to decide that it doesn’t agree with their digestive system!

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