Linda and I are in Sacramento this week for the National eXtension Conference. I will be presenting later in the week on the work that we have done on the SOME-DED-TREES project. More on that in later posts. In the meantime, here are some photos from the State Capitol Park here in Sacramento. If you are ever in the area, I encourage you to check it out since the Park also doubles as an arboretum. The combination of mild winter temperatures and irrigation allows for as wide an array of trees as you are likely to see on one location. Many, but not all, of the trees have tags with common and scientific names. There are also numbered tags for a “Tree tour”. I have searched several sources for the tour map and came up empty. Judging by the condition of the tags and the number of missing tags, it looks like a forgotten project. If anyone has any insights, let me know. Or if you know an Eagle Scout in the Sacramento area, re-tagging and mapping would make a great project.
Palm tree tagged on the State Capitol Park Tree Tour
Italian stone pine Pinus pinea
Bark pattern (looked to be some type of Cuppressus but tag was missing
Tags need some work…
Lots of nice coast redwoods (Sequoia sempervirens)
Giant sequoia (Sequioadendron giganteum) as a street tree? These actually looked like they were doing well and then hit the wall. Note the fading top.
The park also includes a small rose garden and cactus garden.
You can hedge almost anything if you’re determined, even azaleas…
Just for Linda: Topiary at the hotel across the street.
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.
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
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.
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.
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.
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.
Icing on roadside trees
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.
White pines showed frequent damageSpruces 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.
High crown damage on silver maple
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 damageBaldcypress, 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
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.”
Ice coated Fraser firsOur silver maple did what silver maples do in stormIce coating was over 1′ thick in some casesLot of tree breakage everywhere. I’m surprised anyone has power todayBeautyberryRiver birch laying down on our driveway
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
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.
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.
Just for Linda: Topiary at the hotel across the street.
