The Garden Professors™

FreezePruf revisited

I received a comment over the weekend requesting an update on an article I posted back in February of 2010 (Wow, hard to believe we’ve been at it that long!) about FreezePruf, a product that is purported to improve freeze tolerance of garden plants. The ingredients and proposed mode of action of FreezePruf are described in my earlier post, so I won’t repeat them here. Back in 2010, there were no published studies available on the efficacy of FreezePruf; just advertising claims from the manufacturer and data that were included in the patent application.

Since then, there have been two studies published on FreezePruf. One was authored Dr. David Francko at the University of Alabama, who lead the group that developed the product, and the second study was by Dr. Jeff Anderson at Oklahoma State.

Francko et al. (2011) conducted a series of trials, mainly with palms, oranges, and other warm region plants and found that FreezePruf was often highly effective in reducing freeze injury. For example, the figure below suggests that spraying plants with FreezePruf can increase freeze tolerance by 2.3 to 9.4 deg. F. (Note: the authors’ also included two additional palms and two banana cultivars in this portion of the trial; I have simplified their table to show the two extremes and an intermediate response).

Anderson (2012) applied FreezePruf based on label directions and found no change in freezing point depression in peppers, celosia, or tomatoes. Anderson also found that Freezepruf did not improve cold hardiness of Bermudagrass stolons.

So what gives? Is FreezePruf useful or not and why did the studies reach opposite conclusions? Anderson published his paper after Francko et al. but doesn’t offer a clear explanation beyond the use of different plant materials; with the exception of tomatoes, which were included in both trials but still gave different results. One possibility is that the spray may be more effective on perennial plants, especially on older leaves. For instance, in the Francko et al. study they applied FreezePruf to young and old leaves on oranges trees and found a greater and more consistent improvement in cold hardiness on the older leaves than the new leaves. For those of us in the northern U.S., this suggests the product may be of limited use. Typically our greatest concern in protecting plants from freezing is early in season; right after we’ve jumped the gun and planted our annuals and vegetable plugs. Could FreezePruf protect your new petunias from that predicted 25 deg. F night? There is no clear answer in the data so I’ll stick with the tried and true and cover my plants with old bedsheets.

Literature cited:

Anderson, J. 2012. Does FreezePruf Topical Spray Increase Plant Resistance to Freezing Stress? HortTechnology 22(4):542-546.

Francko, D.A., K.G. Wilson, Q.Q.Li, and M.A. Equiza. 2011. Topical Spray to Enhance Plant Resistance to Cold Injury and Mortality. HortTechnology 21(1):109-118.

Tell us how you really feel…

I nearly caused a wreck trying to get this photo.
Feb. 19, 2014. Blacksburg, Virginia

Must be a gardener!

A DIY Debunking Guide

Debunking myths is at the heart of the Garden Professors blog. The impetus for initiating the blog is rooted in Linda’s ‘Horticultural Myths’ Series and Jeff’s “The Truth About…” books. Unfortunately, I’ve never been especially good at myth-busting or debating. When confronted with someone with deeply held beliefs that are based on misinformation, it usually doesn’t take long for me to lose my cool and my arguments devolve into, “Pull your head out of your a— and face the facts…”

At a holiday dinner not too long ago, a relative suggested “You know, there may be something to the anti-immunization thing…” The words were barely out before I could feel my wife’s hand on my thigh in a futile effort to keep me calm. “Are you fricking nuts?” I shot back automatically. “The only reason Jenny McCarthy or anyone else can even THINK about not vaccinating their kid is because the rest of the herd already took care of business.” Fortunately cooler heads at the table changed the subject before the debate escalated to violence.

Now for the myth-busting challenged among us, Australians John Cook and Stephen Lowandowsky have developed the Debunking handbook. The guide looks at some of the psychology of myth-busting (A simple myth is cognitively more appealing than an over-complicated correction) and suggests debate strategies (Adhere to the KISS principle). The guide is linked at the SkepticalScience website and is largely geared toward dealing with climate change deniers, but the principles and tips are useful for dealing with all manner of scientific misinformation

It came from the blog… The return of SOME-DED-TREES

Things have been going fast and furious here since the start of the year. We still have a few days left in February and I’ve already logged 13 talks in five states. Nevertheless, I’ve manage to find a little time to crunch some data on SOME-DED-TREES. For the uninitiated, SOME-DED-TREES is the acronym for the Social Media Designed Tree Transplant Study. The project was an opportunity for Garden Professor blog readers to participate in the design of a landscape horticulture research project. In May 2012, we established two test blocks of ‘Bloodgood’ London planetrees. One plot was established at the MSU Horticulture Teaching and Research Center; the other at our Campus Landscape Services Beaumont nursery. All trees were planted from 25 gallon containers (avg. height 12’, avg. caliper 1.8”). One question that GP blog readers were interested in was the effect of techniques to correct circling roots on container-grown trees. So at each location we divided 48 trees into three groups. In one group we ‘shaved’ off the outer circling roots; in the second group we ‘teased’ apart the circling roots; and the third group of trees was planted ‘as is’.

We looked at an additional treatment factor at each of the two locations. At the Teaching and Research Center we mulched half of the trees with 3” of coarse pine bark and left the remainder without mulch. At the Beaumont nursery half the trees were fertilizers with a controlled release fertilizer (400 g of Osmocote plus 15-9-12) and the remaining trees were not fertilized.

Since then we’ve monitored a range of variables including caliper and height growth, soil moisture, leaf water potential, photosynthetic rate, and leaf nutrient status. Two growing seasons after transplanting here are some key findings.

Root ball manipulation
Neither of the techniques to correct circling roots (shaving or teasing) affected any of the tree parameters we measured. There was no difference among root treatments in caliper growth (Fig. 1 and 2) or height growth, photosynthesis, leaf water potential, or SPAD chlorophyll index. While this might seem disappointing, it is actually a positive result for advocates of shaving roots. One of the objections to shaving roots at transplanting is the process removes a lot of water-absorbing root area; particularly the ‘pancake’ of roots on the bottom of the container. We planted our trees just before the severe heat and drought of Summer 2012, and there were no obvious stress-related impacts of the root treatments. Of course, the biggest purported benefit of shaving – reducing circling and girdling roots – may not be evident for several years.

Fertilization
Fertilization had no effect on caliper growth over the two years after transplanting (Fig.1). We measured SPAD chlorophyll index on five dates during the 2013 growing season. Fertilization increase chlorophyll index from 34.0 for the control trees to 35.5. What does this mean? Probably not much. Proportionately this is a very small increase. Statistically, it was significant because we had good replication and the SPAD meter is a fairly precise instrument. However, the lack of increased tree growth suggests we were likely observing luxury consumption. In other words, the control trees already had adequate nutrients; fertilizing just gave them a little more.

Fig. 1 Two-year mean stem caliper growth of London planetrees subjected to root-ball treatments and fertilization.

Mulch
Here’s where things get interesting. After two years, mulching increased stem caliper growth of the planetrees by an average of 70% over the trees without mulch (Fig.2). For stats junkies scoring at home, that corresponds to a p-value of 0.001. What’s going on? Well, we know that mulch provides many benefits for trees. The biggest in terms of tree growth is conserving soil moisture. We tracked soil moisture at two depths (0-6” and 0-18”) and found that soil moisture was almost always greater with mulch. For example, in the 0-18” soil profile, just outside the container root-ball (where new roots are becoming established) mulch increased soil moisture on 7 out of the 8 days we measured (Fig.3). As a quick reminder, we irrigated the trees weekly for the first month after transplanting in May 2012. After that, they were not irrigated.

Fig. 2 Two-year caliper growth of London planetrees subjected to rootball treatments and mulch. * indicates mean between mulched and non-mulched trees is significant at 0.001.

Fig. 3 Mean soil moisture at 0-18″ depth for London planetrees with and without mulch. * indicates means for a given date are different at 0.05.

What’s next?
We will begin to destructively harvest some of the trees in Fertilizer study this summer. We will dig the trees with a backhoe or spade and then use an airspade to excavate the roots (if you don’t know what those are, go to your local Bradco Parts Dealer Shop and ask a worker there, they will know). Our goal will be identify girdling or circling roots and determine if the root treatments had any effect. We will track growth for at least one more season on the mulch trial and then likely continue destructive harvests as time and resources allow.

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