The Garden Professors™

How cold WAS it?

The line ‘How cold WAS it?’ has been a lead-in for stand-up comics for years; as in, “It was so cold politicians had their hands in their own pockets…” or “It was so cold the mice were playing ice hockey in the toilet bowl…” Like everyone, I’ve heard lots of discussion these days about just how cold this winter has been. We certainly know that this winter bucks a recent trend of relatively warm winters in the Midwest over the past two decades.

However a popular notion around these parts, especially among old-timers, is that “this is the way winters used to be…” I’m a relative newcomer to Michigan, currently experiencing my 15th winter here. This is, by far, the coldest winter since I’ve lived here. But could this simply reflect my lack of perspective as a newbie? To gain a little insight, I pulled the long-term weather data for Lansing, which dates back to the 1880’s. I compared the daily minimum temperatures from this winter with the long-term average low temperatures and daily record lows.

The results will come as no surprise to anyone who lives east of the Rockies. It’s been cold. How cold WAS it? Certainly well below average, especially since the Holidays. As of yesterday, 41 of the last 52 daily lows have been below average and we have been below 0 deg. F 19 times. Despite the prolonged cold, we have not broken any daily records although locations near here have.

So, are the old timers right? Are we just getting a glimpse of the way things used to be back in the day? The data suggest they are probably experiencing a bit of selective memory. If you’ve lived here long enough you’ve seen a few winters this cold and even colder. But this January will go down as one of the 10 coldest (at least) on record, so the idea that winter’s weather is like the ‘old normal’ is a bit of a stretch.

University of Florida study: Mulch reduces soil water loss to evaporation by 33%

I was just in Fargo for the North Dakota Urban and Community Forestry Association conference – our pantywaist -12 deg. F wasn’t cold enough – I wanted to experience some real winter. Dr. John Ball from South Dakota State University, whom I enjoy listening to, was also on the program. As an aside, if you are ever invited to speak at the same conference as John, DO NOT allow yourself to be scheduled after him. He is hilarious and you will sound like a boring moron by comparison. John is an excellent and entertaining speaker and I usually agree with 90+ % of what he says. In this case he was talking about mulch – a subject near and dear to my heart – and lead off by mentioning the recent study by Gilman et al. (2012) as a reason why we should be concerned about possible negative impacts of mulch.

Oh boy. Let’s go through this and see what the paper does and doesn’t say about mulch.

The study was done in collaboration with Richard Beeson, who is widely known for his work using weighing lysimeters to estimate water use by container-grown trees and shrubs. In this case lysimeters were used to measure water lost from containers filled with soil or container media (60% pine bark : 30 % peat: 10% sand) and then covered with pine bark mulch or left uncovered. The containers were watered and allowed to drain. Water loss due to evaporation (there were no trees in the containers) was measured for three days. For the first day after watering there was more evaporation from the containers filled with container substrate that were mulched than the containers that were not mulched. However, if you add up the evaporation over the entire 3 days there is no difference between mulched and non-mulched containers. This is not too surprising since the mulch and container media were largely the same thing – pine bark.

Now here’s the important part. If you look at evaporation for the soil-filled containers – which are the ones we really care about from a landscape perspective – total evaporation was 3L for non-mulched containers versus 2L for mulched. In other words, there was much greater water loss from soil when the pots where not mulched. A much better title for the article would have been, “Mulch reduces evaporation from soil by 33%”!

It’s easy to nit-pick articles but this isn’t pit-picking. There is only one table in this article and they got it wrong. For whatever reason people are prone to hysteria when it comes to tree care and I can already see this morphing into “Oh my God! Did you hear? Ed Gilman says if you mulch a tree you’re going to kill it!” A misinterpreted 3-day study has everyone criticizing mulch while ignoring a vast body of long-term studies.

Re-using containers? A cautionary tale.

I attempted to clean up our little home greenhouse over the holiday break. There’s no good place to recycle pots around here, and I hate throwing them away…so I suffer from container build-up. Figured I’d sort through the haphazard pile in the corner of the greenhouse, wash and re-stack the useable ones, and finally ditch the busted ones.

As I started separating the first stack, I noted a tiny flash of red. It is well-known and oft-reported among my gardening and grower buddies that the Southern Black Widow (Latrodectus mactans) really enjoys a nice stack of grubby pots. But I hadn’t seen one in quite a while, and not at our current location.

Boy, did I hit the jackpot.

I’m not afraid of spiders. At all. Quite fond of them, actually – they are immensely useful and fascinating critters. And only a very few pose any kind of danger.
In the case of the Black Widow, a bite injects a neurotoxic venom (latrotoxin). The bites and ensuing symptoms are allegedly quite painful, though rarely fatal. In this instance, I chose not to sacrifice my comfort for our collective edification, i.e. “How Bad Can it Hurt?” (see Blister Beetle post).

So, I squished her. But felt pretty bad about it.
As I worked through the stacks, I found another.

Shook her to the floor and did some more tap-dancing. Perhaps it was time to stop taking pictures and put some gloves on.

By the time I got through the entire pile, I’d found and mushed thirteen of them, sized small through pretty darn large. The landscape fabric on the greenhouse floor was peppered with little beige, black, and red blobs (you don’t need to see that photo).

There were none in the stacks of shiny new nursery pots I’d ordered for our blueberry transplants. But if there was some growing media or plant debris still stuck inside, there was a high probability of finding a spider.

Moral of this story? Think twice about leaving a bunch of dirty plant containers piled up. A simple hosing out before I’d stacked them would have probably prevented such a large infestation.

There’s also a significant chance that I will forget all about the need for caution the next time I’m potting up stuff. Which may lead to an even more educational and entertaining blog post, where I describe “Adventures In Lactrodectism.” Because I’m sure I missed a couple, or they’re hiding in the gravel. As the old saying goes,

“Seeing a spider isn’t a problem. It’s a problem when it disappears.”

New publication on biodynamics

Happy New Year to our blog readers!

Now that we have our blog safely moved to this new format, we all resolve to post more frequently. (It’s actually Bert’s day to post, but given that his computer is probably frozen – literally – in Michigan, I’ll step in.)

Today I got a link to my most recent publication in HortTechnology on the science behind biodynamic preparations. I’ve written about this topic before, but recognize the importance of peer-reviewed information for researchers, extension educators, and Master Gardener volunteers. Not to mention all the gardeners who rely on us to provide good science for gardens and landscapes. So here it is. I’m planning to continue submitting review articles to HortTechnology on other topics of interest. It looks like permaculture might be the next one up.

So enjoy this article – pass it on to others who are curious about biodynamics, and if you are a Master Gardener be sure to take it to your MG coordinator and ask that it becomes a resource for your program.

The Ice-pocalypse of 2013: Winners and losers

Power has been restored to most of the nearly 600,000 people in Michigan that lost electricity during the ice storm that hit last weekend. The storm coated trees with an ice coating an inch thick in many locations, resulting in widespread tree damage. Exceptional events such as this remarkable ice storm provide numerous opportunities to make some observations about trees and how there were impacted by the event. Here are some notes based on observing trees near my home in DeWitt, MI and driving around Lansing, East Lansing, and the MSU campus. Please note these are general trends and impressions. For nearly every item listed I’m sure someone will be happy to point out exceptions.

Conifers vs. Deciduous trees. Without a doubt the ice-storm was much harder on deciduous trees than conifers. Elms, maples, oaks, locusts, and birches were all hard hit by the storm. Conifers, for the most part, came through pretty well. The main exceptions were pines, particularly eastern white pine and Scots pine, which received widespread damage. Firs and spruces generally fared well. A big surprise (at least to me) was that there was comparatively little damage to arborvitae, which often end up splayed after heavy snow. In the current storm the ice tended to meld into a solid coating, essentially fusing branches together and reducing splayage.

Spruces were largely unaffected by the ice load

Old vs. Young. Young trees came out relatively unscathed compared to mature trees. In many cases young trees were bent over by the ice but were recovered after the thaw.
The most common damage that occurred on large trees was high crown breakage. One fortunate aspect of the storm is that there was relatively little wind while the trees were coated with ice. As a result, most of the force on braches was downward and the vast majority of the breakage was on smaller limbs (3-4” diameter). Of course there were exceptions to this, but we did not see widespread uprooting of trees or effects of shear forces that usually accompany wind-storms.

Native vs. Exotic. As one would predict, this one was pretty much a push. Silver maples, which are native to this region were among the most heavily damaged trees. Likewise native eastern white pines and oaks were also widely damaged. Among exotics, Siberian elm and Japanese pagoda tree had extensive breakage.

Almost all Japanese pagoda trees on campus has extensive branch damage

Baldcypress, an exotic in Michigan, had little ice damage

Managed vs. Unmanaged The ice-storm did reveal some cases where regular tree maintenance can pay off. The MSU campus has dozens of English oaks that have been planted over the years. At one point these were thought to be the ‘wonder tree’ that would be perfect for street and landscape planting in the Midwest. And they do have many great attributes; nice form and leaf color, moderate growth rate, tolerance of poor site conditions. Unfortunately they suffer chronic branch mortality due to two-lined chestnut borer. Just a few weeks ago our campus grounds crew came through and did some maintenance pruning on these oaks, removing lots of dead wood from each tree. Since the tree crowns had already been cleaned up, there was almost no breakage in these trees during the storm. One might argue that the net result was the same, whether the arborists took the limbs down or the storm did, but when dealing with trees it’s always preferable to take things out on your terms and timetable rather than the weather’s.

These English oaks lost very few branches during the storm thanks to recent maintenance pruning

(Not so) pretty in Pink

The weekend’s weather forecast portended some lousy conditions and, unfortunately, this time the forecasters got it right. The outlook map for the Lansing area put us squarely in the dreaded Pepto-Bismol pink ‘Icy mix’ swath from Oklahoma to Maine.

Last night and this morning was a non-stop cacophony of “Snap! Crash!” as icy limbs headed earthward. About 4:30 this morning my wife saw a bright flash burst across the street and almost immediately we heard all our of appliances stop. No power. After breakfast I negotiated a slalom course of downed tree limbs to a nearby supermarket which was operating on its emergency generator. Last minute Christmas shopping had instantly given way to stocking up on bottled water, camp-stove fuel, batteries, and Presto logs.

The short drive back and forth to a store made the immensity of the storm immediately apparent. Most people we know are without power and I suspect for most of us it will be several days if not longer before we get it back. Hats off to the men and women that are heading out to get things working again while the rest of us are staying inside and trying to keep warm.

I did get out and get a few photos around our place this morning to share, in case you’re in a location where you’re not experiencing the 2013 Ice Storm up close and personal. My alternative title for the post was “Beauty and the Beast.”

Our silver maple did what silver maples do in storm

Ice coating was over 1' thick in some cases — Ice coating was over 1′ thick in some cases

Lot of tree breakage everywhere. I'm surprised anyone has power today — Lot of tree breakage everywhere. I’m surprised anyone has power today

This gives “cutting the grass” a new meaning.

No, no, no.
NO.

Miscanthus sinensis, shaved into submission. — *Miscanthus sinensis* along the sidewalk in downtown Blacksburg, Virginia. Sheared into submission.

Textbook “right plant, wrong place.” Miscanthus sinensis is tough, drought tolerant, creates a nice screen, and if the late-blooming cultivars such as ‘Gracillimus’ and ‘Morning Light’ are selected, has little chance of seeding all over. After a few years in place, most cultivars are as wide (or wider) than they are tall. The lovely mounding/flowing habit is why this is the number one ornamental grass sold.

Mounded, rounded habit of Miscanthus as used at the Sarah P. Duke Garden (Durham N.C.). — Mounded, rounded habit of *Miscanthus* as used at the Sarah P. Duke Garden (Durham N.C.).

A better option – a very upright grass such as Calamagrostis x acutiflora ‘Karl Foerster.’ Regardless, this stuff needs to come out. Depending how long it’s been in the ground, a backhoe with probably be required. Or, they can continue carving it into a pillar.

The ins and outs of trunk injection

I am serving on a Ph.D. committee for a student working in Entomology and Plant Pathology who is defending his dissertation tomorrow morning. I’m taking a break from trying to plow through the longest dissertation in history: A 465 page tome on the use of trunk injection in tree fruit crops. A lot to wade through but a fascinating topic. Trunk injection, of course, is not a new topic. Some of the earliest references to injecting compounds into trees date back to Leonardo daVinci, who also suggested the ‘pipe model’ theory of tree architecture; the notion that total cross-sectional area of a tree is constant as you move up to higher and higher levels of branching.

daVinci's notes on branch architecture — daVinci’s notes on branch architecture

Trunk injection can be useful in lots of applications. We have done some research in my lab on the use of trunk-injected imidacloprid for treating ash trees for emerald ash borer. The compound is highly effective against the beetle but using C-14 radio-labeled imidacloprid we were able to demonstrate the flow up the trunk of ash trees can be ‘sectored’, potentially resulting in ‘hot’ and ‘cold’ spots in the crown where the adult beetles feed on leaves.

Injecting 14C-labeled imidacloprid into ash trees.

On the MSU campus our arborists have been successfully using trunk-injected fungicide applications to protect our remaining elm trees from Dutch elm disease (DED). Prior to the arrival of DED the MSU campus had about 3,000 elm trees; today we have less than 300. Under the current program the trees are treated with propiconazole in a three-year rotation; 100 trees each year. We still lose a tree or two each year but the program is largely effective.

Elm trees used to be a dominant feature of the MSU campus, now they are specimens.

One application of trunk injection of which I am dubious is for treatment of nutrient deficiencies. It’s not that trunk injection is not effective for this purpose; in fact, it is often highly effective. The problem is treating nutrient deficiencies with trunk injection just treats the symptom rather than the underlying cause. Here in the Midwest a common scenario is iron chlorosis in pin oaks. The fundamental problem is that alkaline soil conditions limit iron uptake. The solution? First, right tree – right place. Don’t plant pin oak if you have alkaline soils. Second, if it’s an existing tree, work on lowering the pH with sulfur or ammonium sulfate. Remember, trees have evolved or God designed them – take your pick – to take up nutrients through their roots. Dealing with that end of the equation is the best solution in the long run.

Trunk injection can be used to treat iron chorosis but can sometimes cause more problems. Injection of ferric ammonium sulfate burned leaves on this tree.

Conventional vs. organic agriculture – the battle continues

An article was published earlier this week comparing the nutritional content of milk from organically raised cows to that from conventional dairies. The principle finding in this report is that “organic milk contained 25% less ω-6 fatty acids and 62% more ω-3 fatty acids than conventional milk, yielding a 2.5-fold higher ω-6/ω-3 ratio in conventional compared to organic milk (5.77 vs. 2.28).” (ω-3 fatty acids are considered to be “healthy” and you’ve probably heard of them in association with fish consumption.)

Of course, the popular press has had a field day with this, with such headlines as “Study finds organic milk is more nutritious.” This of course is nonsense, because the researchers didn’t study the health effects on people consuming the milk. But for argument’s sake, let’s assume this might be true and move on to the study itself.

What researchers actually found was that cows who feed primarily on pasture grasses and other forages (the “organic” cows) had elevated ω-3 fatty acids compared to those receiving a primarily grain-based diet (the “conventional” cows). This isn’t new information – other studies (such as this one) have consistently demonstrated this.

The problem with this newest paper is the inaccurate terminology used to describe the study. It really has nothing to do with whether the cows are raised organically or conventionally – it has to do with what they eat. A better experimental design would have included multiple comparisons among “organic” cows (who by default are grass-fed), “conventional” cows that are fed a grain diet (typical with large operations), and “conventional” cows that are pasture-raised (common with smaller farms that don’t want to jump through the organic certification hoops). I’m betting that the milk from this last group of cows wouldn’t be much different from the “organic” cows.

The upshot of using such imprecise terminology is that the message is lost amid the furor of the ongoing organic vs. conventional agriculture battle. Readers erroneously jump to a value-based conclusion – i.e., organic is “better” than conventional.

In my opinion, there’s no excuse for this. The experts who reviewed this article should have pointed out the loaded language and insisted on a change in terminology. (You might be interested to follow the comments on this article, one of which alludes to misleading terminology.)

Does anyone really know how to handle weather ? – revisited

There are few things that bind us together like weather. No matter what a person’s socio-economic status, they get wet, hot, or cold just like the rest of us. Ok, if you’re rich enough you can afford to move where the weather suits your clothes, but if you’re like most of us, you have to deal with whatever Mother Nature sends your way. And, if you’re a typical American, few things give you more self-righteous satisfaction than knowing that out of the 300 million people in the country, YOU are the only one that knows how to cope with weather. So as this weekend’s winter storm brought wintry conditions to parts of the country that don’t often see snow, I could hear people chortling smugly from Buffalo to Fargo. Of course people in Dallas don’t know how to drive in snow; why the F#@$ would they? The chortlers also conveniently forget that that first full-on snow usually brings plenty of misery to northern climes as well.

It’s all basically a cycle. Someone, somewhere, sometime will be laughing at you and your neighbors. People from the Northwest snicker when schools in the Midwest delay their start because of fog, people in Michigan laugh when the South gets snow, and people in the South can’t understand the hysteria of a Midwestern heat wave. But thanks to Jimmy Kimmel, at least we can all laugh at southern California.