My Favorite Class Project

Every year  I teach a class called nursery management.  In this class students have the opportunity to try all kinds of different growing techniques out in the nursery.  They get to use a tree spade and prune and all kinds of other stuff.  But something else that I have the students do is to make hydroponic systems for growing plants.  No, hydroponics is not a common technique for growing plants in a nursery, but to grow plants hydroponically you need to know what you’re doing, and so this is a convenient way to make the students think about the plants they grow and what these plants need to prosper.

To start this project I give the students a water pump and an air pump (courtesy of our friendly neighborhood drug dealers — no, seriously — when the cops bust pot growing operations they give us the equipment that they’ve confiscated after they’re done using it as evidence.  Much of the equipments is new, some is very high end.)  Then I divide the students into a few groups, tell them what they’re growing, and give them two weeks to come up with a growing system and a nutrient solution to grow their crop (I do allow them to use our stock hydroponic solution, which will grow the plants, but won’t win anyone any prizes — most groups choose to use this as a base solution and then add to it.).  The group whose plants grow the largest after twelve weeks wins a modest bonus to their grade.

So, what do we have for set-ups this year?  Some very, very cool ones!  First, we have a number of groups who went with a simple, non-circulating system, as seen below.  Basically just an air-hose and a container filled with nutrient solution.

Another group decided to use a flood and drain system.  They use a timer to trigger the water pump to fill a tray with nutrient solution for five minutes every few hours.  This hydrates the containers which hold the extremely well drained ceramic beads in which the plants are held.

And finally, one group decided to use a capillary action system where the base of the container is filled with nutrient solution which is wicked up into a well drained media (a combination of rockwool, vermiculite, and perlite) into which the plants are placed.  This group decided to lay their plants on their sides to encourage extra root growth.

I’ll let you know in about 12 weeks which group wins!

Buddleia or Buddleja?

I recently heard that Mike Dirr has come out with the next edition of his book on woody landscape plants. Dr. Dirr (I can’t seem to bring myself to call him Mike, even after all these years) was my major advisor in graduate school, so I’m really looking forward to getting it.  In the meantime I heard that he included a section on my thoughts about how to spell the scientific name of the butterflybush, a plant that I worked on to get my Ph.D..  Some people spell it Buddleia, but most go with the Buddleja spelling  — but it looks really silly.  So, while I’m not sure exactly what Dr. Dirr wrote, I thought I’d give you my two cents worth.

By the way, any of you out there yelling and screaming that I shouldn’t be promoting an invasive weed should be ashamed of yourselves.  I spent years working on this plant and I refuse to believe that all of my work was for naught!

But back to the name. First of all you need to understand that the Butterflybush was originally named for a botanist named Adam Buddle.  Buddle didn’t discover this plant.  Nor was he directly involved with its naming, being an expert on mosses.  Besides, he wasn’t even around when Butterflybushes were discovered by the western world around 1730 (Buddle died in 1715).

Buddleja was first mentioned in Species Plantarum, a book by Linnaeus.  And, when it was listed there, it did have that j in it.  OK, so far it makes sense to spell the name Buddleja. BUT, in his later works, though this plant was spelled Buddleja in the text of the book (at that time stylized print settings meant that i’s were printed as j’s u’s as v’s as s’s as f’s), in the index – where the stylized text wasn’t used – Buddleia was spelled with an i.  Hence I submit to you that Buddleia should be spelled with an i – though I’m not nearly as fanatical about it as I once was.

Slugs and Beer

Around my home I have gravel and hostas.  Just perfect, as you might imagine, for lots of slug damage.  This is where I do my work on slug remedies.  And there are lots of remedies for slugs!  One of the oldest of these remedies is beer.  Almost any beer will be adequate (including alcohol free), but generally the darker the beer the better.  When I first started testing different cures for slugs about five years ago one of the first ones that I looked at was beer.  And when I first tried it…..well, see for yourself.

This is the way that I set up my first beer trap (for this test).  There’s fine sand all the way around the trap and the trap is filled with Moose Drool (a nice beer — Suzanne, my wife — was actually a little irritated that I wasted a good Moose Drool when we had a Bud Light in the fridge — But I was only thirsty for half a beer when I set it out….and I don’t like Bud Light)

I set this trap up around 8 o’clock on a nice warm summer evening, the idea being that the next morning I could go out and see how many slugs approached the beer (by looking at the sand) and then see how many slugs the beer actually caught.

As you can see below we had quite a few slugs approach the beer (By my count about twenty).  And guess how many dead slugs were in that beer?

If you guessed 20…you’d be wrong!  There were no slugs in that beer.  Why?  Because this is a poorly designed slug trap!  slug traps are best when they are made with something like a mason jar and that jar is buried up to the lip of the jar in soil.  Then the jar should be filled up to within about an inch of the top with beer.  If you fill it higher the slug will be able to just reach his head in and drink.  In fact, after I set this trap out, I spent much of the evening watching slugs do just that — it was actually a little like watching old episodes of Cheers!  I had names for the slugs and everything (like Norm and Frazier and that mailman guy whose name I can’t remember now…).

So slug traps are good — but only if they’re set up right!

Bags and Apples

One of my favorite garden “cures” is placing a clear plastic sandwich bag around apples when they are young to protect them from insects and disease.  It usually works great and impresses the heck out of people who see and eat the apples which are normally tough to grow without using  bunches of organic or synthetic pesticides.

Unfortunately this year was different.  Rebecca Koetter, the person who planted these trees and put the bags on the apples (on the University of Minnesota campus) discovered that birds may choose to ignore the bags.  And, as if that wasn’t bad enough, Asian lady beetles decided to get in on the fun!

Bare Root Trees

For the past 11 years I’ve been running a nursery at the University of Minnesota called the TRE (for Teaching, Research, and Extension) nursery where we research all kinds of fun stuff like Dutch elm disease, the dangers of mulching, and what happens when you plant a tree too deeply.  One of the most interesting things we’ve done recently, though, is to install Missouri gravel beds into the nursery.  Missouri gravel beds are called Missouri gravel beds because they were invented by Chris Starbuck, a professor at Missouri State.  He mostly works with gravel beds above the surface of the soil, while here at Minnesota we work with gravel beds below the surface of the soil (the gravel bed below is 60 feet by 10 feet and filled with about 2 feet of pea gravel — we do have a system for recirculating the water — which we sometimes use and sometimes don’t because of clogs, algae buildup, etc.).

We take bare root trees and place them into these beds in spring (when bare root trees are available from nurseries) to encourage root growth and then plant them out into the field later in the season.  The amount of beautiful fine roots for transplanting is just incredible, and the resulting plant can be planted bare root any time of year, instead of just spring when bare root plants in our area are usually transplanted.

Now to be a little more specific: I’m a tremendous fan of planting bare root plants, but I’m not a fan of planting larger plants bare root (at least not without Missouri gravel bed treatment), particularly what are known as B&B trees — trees that are harvested and held in a burlap and wire cage, such as those being harvested below from our nursery.

The reason that I don’t like taking a B&B tree and planting it after bare rooting it (by removing all of the burlap as well as the wire cage and then washing off the soil that surrounds the roots) is that, no matter how gently you wash off the roots, fine roots tend to be destroyed.  When you harvest a root ball for a larger tree you are removing about 80-90 % of the roots.  The additional roots that you remove by washing the ball will often make the tree non-viable.  This is something that have I learned from experience with individual trees, as well as from replicated experiments using hedge maples and Turkish filberts.  We used trees with a stem diameter of about 2 inches with standard sized root balls for that size tree, washed off the root ball for half (five trees of each species) and planted the other half using our more standard system (we removed the top portion of the burlap and wire, but not the bottom portion so as not to disturb the ball).  All of the trees which we bare rooted from B&B died after planting and all that we didn’t bare root lived.  This is further supported by some research coming out of the University of Illinois earlier this year by Andrew Koeser (and coauthors) which shows that handling the balls of B&B trees just isn’t that good for them.

So why am I spending so much time with this?  Simple, this is an area where researchers disagree. In fact, based on what Linda has written in the past I’ll bet that she disagrees with me.  And that’s a good thing.  People always want the quick and simple answer, but often there isn’t a quick and simple answer.  I can’t deny that sometimes bare-rooting a B&B tree before planting might be a good thing.  But I think that, in the majority of cases, it’s a mistake.  In terms of containers — We’ve got a big research experiment going on that right now — we’ll have results next year.

No Way! Something that actually works?

Sometimes I feel guilty because I always seem to be putting down the products that people sell to make their living.  But not today!  Today I’ve got something that actually works!  No, it isn’t pretty, and it does have some irritating problems, but I can honestly say that it does what the company that manufactures it says it does.  And that product is the Aqua Globe.

This is a very simple contraption (which is part of the reason that it works).  It’s just a glass ball with a hollow tube connecting to it.  At the base of the tube there’s a hole where water can be poured it to fill the globe.  When you push this into a container it will release the water in the globe slowly and give an extra day or two between waterings.  This contraption doesn’t affect the drainage of the media that you put it into, and it works with most types of media.

The down side to this thing is that….well….it’s kind of nasty looking.  The other problem with it is that, after you push it into the potting soil, it’s hollow tip will fill up with media, so when you fill it with water the next time you need to dig that media out with a fine-bladed knife or a thick piece of wire.  But hey, if you’re going on a short vacation and you’re feuding with your neighbors, then this little contraption will do the trick.

Global Warming, Carbon Dioxide, and Plants

There was an article published recently that traced the melting of glaciers in the US over the last 50 years.  This study showed, pretty convincingly, that the glaciers are, indeed, melting, and melting rapidly.  Meanwhile, in our atmosphere, levels of carbon dioxide from humans burning fossil fuel are increasing in a manner roughly correlated to the increase in temperature that’s melting the glaciers.  But is the carbon dioxide actually causing the warming?  Believe it or not this is still an area of discussion among scientist, and the answer isn’t as simple as many newspapers make it out to be.  Almost all of the scientists that you care to talk to, even those skeptical of the role of carbon dioxide in global warming, admit that increasing carbon dioxide is going to cause a net increase in global temperature.  But there is a decent amount of research out there showing that solar and geothermal activity (in other words things that we can’t control) may cause anywhere from 15 to 75% of the warming that we’re seeing.  To be honest, based on what I’ve read (and I’m no climate scientist), I tend to side with those who believe that global warming is mostly caused by human releases of carbon dioxide, but I also think that to accept that theory as proven is a mistake.

In my humble opinion we’re missing the more compelling reason to reduce our emissions of carbon dioxide (besides the fact that we’re running out of fossil fuels of course).  Plants.  Most people simply assume that, temperature increases aside, increasing carbon dioxide in the atmosphere is going to be good for plants, and that’s just not the case. True, some plants, like Canadian thistle and many other weeds, love the increase in carbon dioxide, but other plants, such as many grasses, just don’t respond to it that well.  The ironic thing is that, for those plants that respond strongly to CO2, nutrients like nitrogen and potassium are taken up quickly from the soil (as you’d expect with a rapidly growing plant) and then, as the nutrients in the soil run out, the growth of the plant is drastically reduced.  In other words, CO2 causes unfertilized soils to become more rapidly depleted.  So what does this all mean?  It means that as we increase CO2 levels in the atmosphere we’re changing the world’s ecosystem, including the fields that grow our crops.  Indeed, we’re actually adjusting the atmosphere to alter which plants are most appropriate for certain situations.  There are even those who argue that, because of our CO2 emissions, we’re encouraging invasive plants to take over our native forests because these plants tend to be able to handle high CO2 (and high temperatures) better than the plants that are already there.

To me this is the more important reason to reduce our carbon footprint.

The Pile Of Ash On My Floor

Part of the problem with being a professor is that companies assume that I have a bottomless supply of funds to test their products and that it is, in fact, my duty to do so.  And of course they assume that this testing will ultimately find their product useful.

The truth is that I do love to test things, but I don’t have the funds to do the comprehensive tests that these companies usually want, at least not without them helping out at least a little – and most of them don’t want to spend money on tests!  But many times, even if I tell them on the phone that I’m not likely to test what they’re selling they’ll send along a sample anyway, hoping that I’ll be curious enough to give the stuff a shot.  And I usually let them because, well, why not?

Anyway, that brings me to this pile of ash that is currently sitting on my floor.  A guy from a company (which I will decline to name) called me on the phone and convinced me to accept about 25 pounds of rice hulls that had been burned to ash while being used to fuel something or another (I can’t remember what and there was no note in the box).  This ash is supposedly the cat’s meow for helping the media in containers to retain water and this guy wants me to test it.  I told this guy that I was unlikely to have time for it, but he was insistent.  I guess he thought that if the stuff sat on my floor long enough eventually I’d get curious, open the box, and try it out.

Turns out he was right.

So I get this box full of ash, open it up and am immediately hit in the face with black dust which I wisely (and accidentally) inhale.  Lovely. Then I take out the MSDS sheet (Material Safety Data Sheet – required for most chemicals) and read about the problems with this product.  It turns out this stuff contains crystalline silica (no surprise there, rice hulls are full on silicon), which can cause a rapid onset of silicoses as well as being a cancer hazard (crystalline silica is a known carcinogen if it’s inhaled).

Now I don’t want to blow the danger of this stuff out of proportion.  I have little doubt that my exposure to it wasn’t enough to do anything terrible to me (just as I’m pretty sure that the two packs of cigarettes or so that I smoked during college aren’t going to eventually lead to lung cancer).  And I’m all in favor of using industrial byproducts for other purposes whenever possible.  But my goodness, this stuff is ash!  It just flies into the air!  I just can’t see how, even with the recommended protection, nursery workers could avoid inhaling this stuff on a daily basis if they were using it to pot up plants (perlite is pretty bad – but this stuff is worse) — which just seems like a heck of a bad idea.  In terms of the ability of this stuff to hold water….well, I put some into a plastic container with some water which the ash absorbed none of.  All that said, it might be possible that this stuff helps container media to hold more water, but for an unintended reason.  This ash is extremely fine.  When we mixed it with container media it quickly found its way into all of the pore spaces between the media particles making the media more like clay than media. This did potentially increase the media’s ability to retain water, but decreased its ability to hold air – which is not a good thing for young roots.  So the quick and easy summary is that rice hull ash is not the best idea for containers.

Mulch Volcanoes

After Linda’s post yesterday I just had to add my own 2 cents about gator bags.  I use ’em and I like ’em.  But, that said, I never allow gator bags to sit against trees for an extended period of time  (Maybe 6 weeks when the tree first goes in).  That’s just asking for trouble!  But looking at those bags got me thinking about a project which we’re finishing up this year.  Volcano mulching. Believe me, it sounds a lot cooler than it is.  Volcano mulching is when you make a big pile of mulch along a tree’s trunk, as in the picture below.

The reason we’re looking at volcano mulching is that everyone says it’s bad, but no-one has really proven that it’s bad.  The reasons that volcano mulching are supposed to be bad are twofold:  First, the mulch could cause rot on the tree’s stem (as with those gator bags) and second, because it might be possible for a tree’s roots to grow up into the mulch, potentially surrounding the stem, which might lead to the roots choking the stem as the tree grows larger.  Not a good situation.  Anyway, early in 2007 we took a field of maples and cut squares in their trunks, as seen below, and then either did or didn’t mound up mulch around these tree’s stems.

What we expected to see was that, over time, the wounding and presence of a mulch volcano would lead to diseases in the stem.  Instead what we found is that, for many of the trees, deeper mulch actually led to the wounds closing more rapidly.  The image below is of a wound that was covered with mulch.

While this next image is of a wound that wasn’t covered with mulch.

Of course some of the wounds without mulch closed fine as well, as you can see in the next image.  (Why isn’t anything ever cut and dried?)

So what does all this mean?  Well, nothing yet.  Research is a funny thing: it rarely gives you quick and easy answers.  I won’t recommend mulch volcanoes because we still haven’t examined those roots that may enter the mulch and surround the stem.  And before I say that the volcanoes didn’t affect stem rot in this study I want to take a closer look at those wounds by cross sectioning the tree which we’ll probably do this fall. Plus we’ve got to run statistics on all the different trees….. and then it would be great if someone else would take a stab at this study to confirm what we see…. I tell you what, nothing’s easy.

Introducing Jeff Gillman


I’m an associate professor in the department of Horticultural Science at the University of Minnesota.  Officially I work mostly with trees and shrubs, but I’ve also been known to test things like egg shells for stopping slugs, beer for its qualities as a fertilizer, and milk for its fungicidal qualities.

I come from a small town in Pennsylvania, just west of Philadelphia, where I first learned about growing trees in my parents’ small orchard.  I attended Franklin and Marshall College in Lancaster PA, then earned a masters degree in entomology and a Ph.D. in horticulture from the University of Georgia (which, incidentally, is also where I met my wife).  After Georgia I came north to Minnesota.

I’ve been itching to do a blog for about a year now, one where I could share my “adventures in horticulture,” but I never felt that I had the time to actually put one together.  Then, a couple of months ago, Linda Chalker-Scott (who you’ll meet shortly) from Washington State and I had a conversation which resulted in our getting together with Holly Scoggins from Virginia Tech, James Nienhuis from the University of Wisconsin, and Bert Cregg from Michigan State and setting up this blog.

For now, each of us will be posting one day a week starting on August 3rd.  Before that each of us will post a short introduction of ourselves so that you can get a sense of who we are.  I look forward to blogging soon!