Costs and benefits of pre-plant root manipulation

Spring has sprung here in Michigan; time to get cracking on lots of projects. One of our new projects is an investigation of pre-plant techniques for dealing with root systems on container grown trees. As many of you know, Linda Chalker-Scott is advocate of bare-rooting trees before planting to correct potential root defects before planting. As some of you may know, I’m skeptical of this approach. It’s not that I think root systems are perfect – far from it. But we lack sufficient information to know whether the costs of bare-rooting (time/effort, stress on the trees) warrant the benefits. We also have little information on how species vary in responding to bare-rooting. From the experience of foresters and bare-root liner nurseries we know that some species are highly sensitive to storage and handling when they’re bare-rooted. When I worked for International Paper, we had little difficulty transplanting sycamores bare-root; whereas we often encountered severe dieback or mortality with sweetgum. Likewise, shade tree nurseries often encounter difficulty establishing oaks, baldcypress, and hackberry from bare-root liners. In fact, J. Frank Schmidt and Sons nursery, one of the largest producers of shade tree liners has discontinued production of bare-root hackberry lines and only produces them as container stock.

As I said, I’m skeptical that putting a tree through the trauma of bare-rooting is worth the potential benefit. But I’m also open-minded and willing to conduct an objective trial to see what’s what. As an aside, I was skeptical about root-shaving before we conducted our own trial and was impressed by the results. For our current study we planted 96 container-grown shade trees last week at the MSU Horticulture Teaching and Research Center. Trees includes three cultivars: ‘Bloodgood’ London planetrees, columnar tulip poplar and ‘October glory’ red maple. We assigned the trees at random to one of four treatments: Control (no root treatment), Shave (outer roots removed before planting) and two bare-root treatments – Bare root – Wash (trees were bare-rooted by washing the roots with water) and Bare root – Airspade (trees were bare-rooted using an airspade). The planting crew consisted of my technician, Dana Ellison; my new Master’s student, Riley Rouse; my undergrad assistants, Becky Pobst and Alex Love; and Linda, who was on-hand to provide quality control on the bare-rooting operations.

For her M.S. project, Riley will be tracking performance of the trees over the next two years. Her measurements will include tree survival and growth as well as measures of physiological responses such as plant water potential and photosynthetic gas exchange. Next fall, after two growing seasons, we will dig a subset of the trees with a tree spade and inspect the root systems to determine the effect of treatments on root system development. In the meantime, here are some photos from last week’s festivities.

 

Right tool for the job. MSU Beaumont Nursery provided a big assist by augering the planting holes.
Tulip poplar roots before shaving
Tulip poplar after shaving
Alex cleans up a planetree with the airspade
Dana’s excited to be washing roots.
Riley washing up a maple – don’t worry the cicling roots come off next…
Light and easy. Becky after airspading a tulip poplar
Wait’ll purchasing sees this… A wading pool is perfect for pre-soaking roots before washing and for storing until planting.
Easy to smile when it’s a Control tree…
Getting a little kinky… Root at the end of the felco’s bending back on itself – corrected after the photo-op.
Looking a little wilty. TheBare-root maples required the greatest root removal and correction
Trial plantation at the end of the planting
Can’t pull off something like this without an awesome crew!

Another good reason to mulch

Posted by Bert Cregg

Researchers often get accused of concluding the obvious.  At some point we’ve all scoffed at headlines like, “Study finds cell phones and driving don’t mix” or “Researchers discover high heels make your feet hurt.”* But even when a study demonstrates something we already know, sometimes there is still value in being able to put hard numbers on the scope of the problem – and hopefully spur some action.

A case in point is a recent study by Justin Morgenroth, Bernardo Santos, and Brad Cadwallader at the New Zealand School of Forestry, “Conflicts between landscape trees and lawn maintenance equipment – The first look at an urban epidemic” Urban Forestry and Urban Greening 14:1054-1058.  Morgenroth and his colleagues surveyed over 1,000 trees in public greenspaces (parks, cemeteries, campuses) in and around Christchurch, New Zealand (pop. 375,000) to assess the amount of damage to trees by lawn equipment.  Their conclusion: Lawn equipment is hell on trees.  This conclusion, of course, surprises absolutely no one that has ever looked at trees near turf in a public place on this planet.

lawn mower blight 2

 

Morgenroth et al. claim their survey is the first systematic look at this issue and their data are staggering.  Nearly two-thirds (63%) of the trees they surveyed had at least one wound.  The proportion of trees with wounds was fairly constant regardless of type of planting (i.e., park, campus, cemetery, roadside verge), though trees in parks and campuses tended to have more wounds per tree than trees in nature reserves or roadside verges.

Not all the news was bad, however.  Morgenroth et al. found that grass cut-outs or mulching around trees significantly reduced the number of wounds per tree.

So, not a conclusion that should take anyone by surprise, but some sobering data to put some scale on the size of the problem.

 

*actual conclusions from real studies

Just post some pretty pictures or something

Posted by Bert Cregg

A little over six years ago Jeff Gilman called me out of the blue and asked me to be part of a new blog about the science of horticulture that he was embarking on along with Linda Chalker-Scott.  I was reluctant – I didn’t know much about social media at the time and was plenty busy already.  Jeff explained that he was recruiting others and how we would rotate posts. I asked Jeff, “What if I don’t have anything to write about?”   Jeff replied, “Just post some pretty pictures or something.”  So with that long ago conversation as backdrop, here are a few photos from this week’s trip to Hidden Lake Gardens near Tipton, Michigan.

Sugar maple fall color
Sugar maple fall color
Entrance to the Harper Collection of Dwarf and Unusual Conifers
Entrance to the Harper Collection of Dwarf and Unusual Conifers

Taxodium distichum "Pendens' cones

Taxodium distichum “Pendens’ cones

Pinus contorta "Chief joseph'. With apologies to Joseph Tychonievich...
Pinus contorta “Chief joseph’. With apologies to Joseph Tychonievich…

Sassafras albidum fall color

Sassafras albidum fall color

The long and winding road...
The long and winding road…
Sciadopitys verticillata 'Joe Kozy'
Sciadopitys verticillata ‘Joe Kozy’
Abies koreana 'Icebreaker'
Abies koreana ‘Icebreaker’
Taxodium distichum 'Pendens'
Taxodium distichum ‘Pendens’

 

Native vs Exotic: Not as simple as it seems

Lots of discussion recently over on the Facebook side regarding the recent publication in Ecological Letters by Karin Burghardt and Douglas Tallamy, “Not all non-natives are equally unequal: reductions in herbivore β-diversity depend on phylogenetic similarity to native plant community.” http://onlinelibrary.wiley.com/doi/10.1111/ele.12492/full
While there are certainly some things to nitpick in the paper (see Linda’s comments on the Facebook discussion), I think this paper may go a long ways re-shape, and possibly even begin to end, the debate over native versus exotic.

How was the study conducted. In 2006 Tallamy’s group established a series of test landscape plantings. Each planting fell into one of four groups: non-native congeners (species that are not native but have native relatives in the same genus); non-native non-congeners (plants from non-native genera), native congeners and native non-congeners. In 2008, when the trees were about 6’ (1.8 m) tall, they conducted a census to identify and quantify the adult and immature insect herbivores they collected. They analyzed the data to determine the amount of insect herbivore diversity within each planting type. Specifically they looked at what ecologists refer to as beta-diversity, the amount of species diversity among sites. If you’re interested and want to learn more check out https://methodsblog.wordpress.com/2015/05/27/beta_diversity/

So, what did they find? Like every good study on host-insect interactions; the answer is, “It depends.” (BTW, if you’re following along at home the key figure in the paper is Fig. 3). When Burghardt and Tallamy looked at the differences in diversity between adult herbivores on native and non-native congeners, they found no difference. When they looked at differences in diversity between immature herbivores on native and non-native congeners, they found no difference. When they looked at differences in diversity between adult herbivores on native and non-native non-congeners, they found no difference. When they looked at immature herbivores on native and non-native non-congeners, they found a small but statistically significant difference, with higher total diversity for native non-congener.

As an aside, it is also instructive to look the version of Figure 3 presented in the article’s supplemental materials, which has been re-scaled to include zero. Including zero on the scale helps to give a better perspective on the actual variation among means. It’s a little like the “Truth in lending statement” that comes at the end of your credit card bill.

tallmay re-scaled

So, a possible alternative title for the paper could be, “Do native or non-native plants increase herbivore diversity? Most of the time it doesn’t matter.” That said, I think this paper makes a number of contributions and will start to shift native versus non-native debate, and perhaps even signal the beginning of the end. First of all it demonstrates that that non-native species of native genera contribute equally to herbivore diversity. However, I think some of the most insightful information in the paper is buried between the lines and in the supplemental information attached to the online version of the paper. The authors briefly mention that they also looked at guilds (i.e., chewing insects, sap feeding insect, xylem feeders, etc.). Once again the answer of whether natives contribute more to species diversity is, “It depends.” For xylem feeders, for example, diversity was the same for congeners and non-congeners.

To me, this is the level of resolution we need to work to gain a true handle on the situation. I’m not an entomologist and I’ve never played one on TV but I’ve been around these questions long enough to know that different types of insects are attracted to or repelled by different plants by different mechanisms. In one case it’s an attraction pheromone, in another it’s a defense chemical, sometimes it’s leaf toughness or a tree is able to produce enough resin to drown boring insects. An old axiom states that ecosystems are not more complicate than we think; ecosystems are more complicated than we can think. As this paper demonstrates, to think that all the complex interactions between plants and insects can be boiled down to something as simple as native or exotic is hopelessly naïve.

Don’t just stand there like a statue

Posted by Bert Cregg

 

Reading through Linda’s recent article in Arboriculture and Urban Forestry “Nonnative, Noninvasive Woody Species Can Enhance Urban Landscape Biodiversity” (Arb. & UF 41:173-186) reminded me of some thoughts I had while I sat through a talk by Doug Tallamy at the New England GROWS conference back in February.  As most GP blog readers are likely aware, Tallamy is the author of Bringing Nature Home.  The basic premise of the book is that native insects only feed on native plants and therefore the use of exotic landscape plants will cause ecological food webs to collapse and the end of the world as we know it.

 

Looking at things critically, there was certainly plenty to nitpick in the talk.  For example, to illustrate that insects feed more on native than non-native genera, Tallamy contrasted Quercus, a genus that includes hundreds of species distributed across the northern hemisphere, to Ginkgo, a monospecific genus (heck, a monospecific order) with a limited native range in China.  Tallamy also compared the food value for birds of seeds of five native shrubs with five Asian exotics.  The North American plants all had higher nutrition, which leads to one inescapable conclusion: If you’re a bird-lover in Asia you need to plant more exotics from North America.

 

But, as I said, those items are nitpicking.  In an apparent effort to appease critics, Tallamy addresses the question of whether it’s ever OK to plant exotics.  He says yes, but think of them as “statues” – nice to look at but devoid of any ecological value – and then put up a slide of a landscape with a bunch of statues photoshopped in.  All analogies break down eventually but the ‘exotics as statues’ model fell apart before the slide hit ever the screen.  First off, native insects, birds, and other wildlife do utilize nonnative plants and I’ll refer you to Linda’s review and her 100+ citations on that point.  But just as importantly, nonnatives can also provide many of the same environmental benefits as native plants.  Statues, on the other hand, don’t cool buildings, sequester carbon, reduce stormwater run-off, and create vertical structure and cover for wildlife – OK, statues provide perches for pigeons, but that’s about it.  Landscape plants, and trees in particular, can provide a myriad of ecological services – but they can only provide these functions if they are alive to do so. Despite the intuitive appeal of, “Native plants are adapted to our local environment”, in many urban, and even suburban, environments this is simply not true due to urban heat island effects, top-soil removal, compaction and other site disturbances.

 

In his talk, as in his book, Tallamy demonizes the typical suburban landscape showing a photo of an expansive lawn with a lone Bradford pear tree.  OK.  Is the problem here the pear? If we changed the pear to, say, a lone shagbark hickory would anything change dramatically?  No, but this does bring me to a point of agreement with Tallamy.  The fundamental problem we face in our landscapes is lack of diversity; not only species diversity but also structural diversity and age class diversity.  If we can build diversity and generate ecosystem services with natives; great, go for it. But we need to understand that our list of suitable native trees is shrinking (as an aside, ignore Tallamy’s recommendation to plant green or white ash if you live in eastern North America). Vilifying, or even banning, nonnatives will ultimately reduce diversity in urban and community forests and their ability provide ecosystems services, not enhance it.

Show me the data!

One of my favorite bumper stickers from days gone by said simply “Stop Continental Drift”. Good luck with that.

stop_continental_drift_530

Today’s topic deals with another type of drift – a phenomenon one of my professors referred at ‘Bibliographic drift’.   This type of drift occurs when authors cite a paper without bothering to look up the original source.  Then a second author cites original source based on the first author’s paper; then a third author cites it based on the second paper and so on and so forth.  This is why grad students learn that second citing is a cardinal sin.

 

It’s an easy trap to fall into even in the age of access to electronic journals.  It can happen in all sorts of ways, especially if the point the author trying to support is something that is intuitively appealing and not likely to be questioned.  For example, I was recently reading through The Practical Science of Planting Trees by Gary Watson and E.B. Himelick.  It’s a good book with lots of great info and photos but under the section on digging the planting hole there is a subsection “wider is better”.  This is something we all ‘know’ but there is no data with any scientific rigor to support it; at least not that I’ve ever been able to find and I’ve looked repeatedly.  So I was intrigued to see Watson and Himelick cite four papers to support the notion that wider is better. Cool. So I went through the bibliography to look up the citations.

Can you dig it? My former research technician Dana Ellison installs a tree in Detroit.
Can you dig it? My former research technician Dana Ellison installs a tree in Detroit.

First up, Arnold and Welsh 1995. Effects of planting hole configuration and soil type on transplant establishment of container-grown live oak. J. of Arboriculture 24:213-218. This paper doesn’t even discus planting hole width, at least not directly.  The authors looked at various planting hole configurations (round, square, star-shaped) but made a point to keep the planting hole volume the same. Zero points for wider is better.

 

Next, Corley 1984. Soil amendments at planting J. Environ. Hort. 2:27-30. One of the experiments in this paper compared root and shoot growth of four shrub species transplanted from #1 containers into holes that were with 1.75x or 3.5x the width of the root-ball. The author measured root and shoot growth after two years and the results were a mixed bag.  They found the wider hole was better about half the time, the other half of the time it didn’t make a difference.  One point for wider is better (sort of).

Next, Montegue et al. 2007.  Influence of irrigation volume and mulch on establishment of select shrub species Arboriculture & Urban Forestry.  33:202–209.  The title of the paper says it all; the authors compared water relations and growth in response to mulch and irrigation but planting hole size wasn’t included as a variable. (Spoiler alert: mulch improved growth and water relations). Zero points.

Last and most interesting, Watson et al. 1992. The effect of backfill soil texture and planting hole shape on root regeneration of transplanted green ash. J. of Arboriculture 18:130-135. In this study the authors looked at new root growth and shoot and diameter growth for three years after transplanting green ash trees into planting holes that were 1.2x, 2x, or 3x the width of the root ball. And they found… nothing. Well, not nothing but they didn’t find any effects of planting hole size on root density, shoot growth or caliper growth. To help visualize the response I’ve summarized their growth data three years after transplanting below. One point for it doesn’t matter.

Cumulative growth response of green ash trees to planting hole width 3 years after transplanting. adapted from Watson wt al. 1992
Cumulative growth response of green ash trees to planting hole width 3 years after transplanting. adapted from Watson wt al. 1992

 

As a final note I include a photo from the Waston et al. paper 1992.  The photo is fuzzy but the caption should be clear.

watson et al 1992

So where does that leave us? Digging a wider hole doesn’t hurt, except maybe your back. And I think that’s part of the appeal of this advice:  If it’s more work it must be better. Dig a hole 2 times, 3 times, 10 times the width of the root-ball if you want. Just don’t say “Research shows wider is better…” because it’s ambiguous at best.

Spring vs. Fall planting: Where you stand depends on where you sit

I’m reviewing some literature while working on a proposal and ran across a paper by Lisa Richardson-Calfee, Roger Harris and Jody Fanelli at Virginia Tech on the effects planting date on sugar maple trees.  It’s not actually the topic of the proposal I’m working on but the paper caught my eye because spring versus fall planting is one of those questions that just never seems to go away.  In this particular study, balled-in-burlap trees planted at spring budbreak had more new root growth than trees planted in the fall.  So does this mean spring planting is better? Not necessarily.  For container-grown trees the results were basically a wash.  This is fairly typical.  I’ve not done an exhaustive search but I’ve looked at a fair number of studies of spring versus fall planting and they often show no clear trend or some will show spring coming out better or fall coming out better.

So why do we hear so often that “Fall is a great time to plant trees.”  Well, first off, think about who is saying it. Frequently it is nurseries that are looking to unload inventory that didn’t sell during the growing season or landscapers that are looking to keep crews busy during the slow fall season.  But the other part of whether fall is a good time to plant has to do with rainfall and temperature patterns.  Linda Chalker-Scott is an advocate of fall planting.  And for her location in western Washington – and many other locations in the West – this makes sense.  If we look at average rainfall patterns for Seattle (actually Linda is in Puyallup but no one outside of the Northwest can pronounce Puyallup), planting in October – when the rainy season is getting into full swing – makes much more sense than planting in April or May before the summer dry season.

Rainfall pattern for Seattle, WA Source: weather hannel.com
Rainfall pattern for Seattle, WA Source: weather hannel.com

Where I live in East Lansing, on the hand, our climate has a summer maximum precipitation pattern – as does much of the Midwest.  As I’m fond of telling people, there’s a reason Michigan’s Arbor Day is the last Friday in April. Spring is a great time to plant trees here because soil temps are warming and the rainy season is just getting started.

Rainfall pattern for East Lansing, MI Source: weather hannel.com
Rainfall pattern for East Lansing, MI Source: weather hannel.com

What about fall planting in the Midwest? My take is that fall is an OK time to plant trees but not necessarily the best.  We typically will still have some rain in the fall but temperatures are declining quickly. Our average daily temperature in December is 28 deg. F, meaning our soils are beginning to freeze, while the average December temp in Seattle is a balmy 42 deg. F.  That’s warm enough for Linda’s roots to keep growing – well, actually not Linda’s roots but Linda’s tree’s roots.

In any event, if you live in Midwest and other places with a summer max. precipitation pattern, your state’s Arbor Day is a good guide to plant trees.  If you live out West in areas prone to summer drought then fall may be your best bet.  This is also a another example of why it’s good to get your landscape and garden advice from local sources rather than the ‘one-size-fits-all’ advice common in many magazines and gardening websites.

 

 

 

 

 

Richardson-Calfee, L.E, J.R. Harris, and J.K. Fanelli. 2008. Root and Shoot Growth Response of Balled-and-Burlapped and Pot-in-Pot Sugar Maple to Transplanting at Five Phenological Growth Stages J. Environ. Hort. 26(3):171–176.

Back on the High Line again

Earlier this week I was in New York City and got to visit the High Line for the first time.  For those who aren’t familiar, the High Line is an urban park that was created along an abandoned elevated rail line on the Westside of Manhattan.  Linda posted about the High Line a couple of years ago.  Her visit was in late winter so my visit provided an opportunity to explore the park during the height of the growing season.

The High Line runs from West 14th St. to West 34th st.
The High Line runs from West 14th St. to West 34th st.

30 feet above the streets of New York City...

30 feet above the streets of New York City…

The High Line offers sweeping views of Manhattan to the east and the Hudson River on the west.  For most of its length the trail consists of various beds of perennials, trees, and shrubs.  Along the newest, northernmost section of the trail, the plantings give way to beds that have been allowed to re-seed naturally; providing an opportunity to observe urban ecological succession.

Perennial beds along the High Line
Perennial beds along the High Line

Quaking aspen

Quaking aspen

The High Line extends through the Chelsea section of Manhattan, which, according to locals, was a less than desirable location just a few years ago.  With the advent of the High Line, however, Chelsea and adjacent Meatpacking district have become some of the trendiest and hottest real estate in the city.  In fact it’s difficult to get a picture along the highline without a crane in the background. What a stark difference from the acreage for sale in Mission, BC that we visited, too bad we are city people.

The High Line near West 30th St.
The High Line near West 30th St.

The High Line has helped transform a run-down section of Manhattan into some of the hottest real estate in New York.

The High Line has helped transform a run-down section of Manhattan into some of the hottest real estate in New York.

Art is an integral part of the High Line with various sculptures and interactive projects along the way.  During my visit, kids of all ages had the opportunity to contribute to a giant Lego sculpture or add to a giant sidewalk painting.

Is is art ? Or just weeds?  This work is part of a 13-piece installation by Adrian Villar Rojas “…known for his large-scale, site specific sculptures that transform their environs into a vision of their own potential future.” It’s titled “The Evolution of God” aka “A Study in Lambsquarters”
Is is art ? Or just weeds? This work is part of a 13-piece installation by Adrian Villar Rojas “…known for his large-scale, site specific sculptures that transform their environs into a vision of their own potential future.” It’s titled “The Evolution of God” aka “A Study in Lambsquarters”

Interactive art. Kids of all ages take time out to add to a Lego construction project along the High Line.

Interactive art. Kids of all ages take time out to add to a Lego construction project along the High Line.

The first section of the High Line opened in 2009 and for the most part it seems to be holding up well.  Some sections of the trail bed are constructed from crushed aggregate and these sections are pretty well pot-holed, presumably from freeze-thaw cycles.  Most plants along the trail seem to be healthy and thriving, likely thanks to drip irrigation.  It will be interesting to see how the trees and shrubs continue to develop and how things perform over the long haul.

Sassafras
Sassafras
This sidewalk fountain provides a change to cool your heels on a warm and sticky New York afternoon.
This sidewalk fountain provides a change to cool your heels on a warm and sticky New York afternoon.

Bottom-line: If you’re in New York and you enjoy plants and watching people (and watching people enjoy plants), a couple hours on the High Line will be time well spent.

Hibiscus
Hibiscus

 

Stuck in the middle with you

Clowns to the left of me,

Jokers to the right, here I am,

Stuck in the middle with you

 

More than once in the past couple months I’ve come close to pulling the plug on FaceBook.  What started as a fun and easy way to keep up with family and friends back home and stalk old girlfriends has devolved into an infinite do-loop of whininess, acrimony and vitriol over GMO’s, organic food, vaccines, and President Obama.  Of course, I brought a lot of this on myself based on the virtual company I choose to keep.  While my allegiances generally align with groups such as GMOLOL, GMOskepti-forum, and the Genetic Literacy Project, more and more I find myself just as appalled by their tactics and rhetoric as I am by those of the anti-GMO side.  I have many thoughtful and intelligent friends that think GMO’s should be labeled or even banned and I’m fairly certain none of them want poor African children to go blind.

greenpeacerice

Quick aside here: Raise your hand if you have ever changed your mind on an important issue based on an internet meme.

2958d9dc0b3f2d0fb38413122b86e2b8

The problem in this type of discourse is that everything has become an all or nothing game.  If you concede even the slightest point to the other side, you have become a wishy-washy capitulator.  But the underlying problem is the answer in science is often “It depends.” In the GP blog and elsewhere, much has been made of the Pew Research poll that showed the biggest opinion gap between the scientists and the public was over GMO safety.  Had I been polled, I would have agreed that GMO’s are generally safe.  But that doesn’t mean I don’t think there are concerns. Heavy agricultural use of glyphosate is leading to the development of Round-up resistant weeds. Likewise, the potential of GMO crops out-crossing with native plants cannot be discounted.  Scientists working on GMO’s, of course, are aware of these issues and are constantly working on steps to manage and minimize these risks, but they could still come back someday to bite us in the butt – the risks, not the scientists.

d0bvh

Another problem with controversies on the interwebs is that issues get over-simplified.  The endless argument over organic food is just stupid.   Saying organic production is better than conventional farming (or vice versa) is like saying Ford is better than Chevrolet:  You can’t compare without knowing which model: Pick-ups? Sedans? SUV’s?  Or  what’s being compared: Gas mileage? Crash safety? Resale value?  The same is true with organic vs conventional: What crop? Celery? Apples? Carrots? Lettuce? And what measure? Pesticide residue? Carbon footprint? Food safety?  The debate is an interminable game of whack-a-mole. I suspect anyone with access to ‘Web of Science’ and an afternoon to kill could come up with a couple dozen studies to support either side.  My personal view is I’ll pay a modest premium for organic produce if it clearly looks better, or in the case of small fruits that I can sample before I buy, tastes better than the conventional counterpart.

images

The other issue in the social media wars is that we need to admit and accept the limits of our knowledge.  The Pew poll and other surveys indicate that most scientists agree that climate is changing due to human activity.  Again, I’m with the majority of scientists on this.  But only a small portion of those scientists are actually trained in climatology and understand and appreciate the nuances of the Global Circulation Model or the Pacific Decadal Oscillation. What I know with certainty is that CO2 and other greenhouses gasses have risen consistently and dramatically since the Industrial Revolution.  How will that impact climate in 100 years?  I have no clue beyond what the climate scientists tell me.  Do I have any reason to doubt their projections of steady increased temperatures? None beyond the fact the GCM, like all models, is only as reliable as the data and assumptions it is built on.  Does this make me a right-wing climate change denier?  Hardly.  But I am self-aware enough to know what I don’t know.

post-57707-Groundhog-Day-meme-Imgur-Only-gmvA

Bottom-line, even on issues where a vast majority of scientists agree, there are still unanswered questions and areas of uncertainty and always will be.  In the meantime, we still have to make policy decision with the information at hand.  Talking about these issues intelligently and respectfully will get us further than derision and mockery.

b48dad3d48ea96ae1cdfc1bed575abd12d4265e243dd6211a06e99d12a3a1acd

In the meantime, if you open up FaceBook and I’m not there, you’ll know I’ve finally had my fill.

A tale of two winters

I’m not sure we’ve ever been quite so ready for the calendar to turn to March. That’s assuming, of course, you live somewhere east of the Rockies. For people on the west coast, the sentiment is probably, “When are those people back East ever going to quit b-tching about their weather…” While I was dealing with 10” of snow and 25 mph winds whipping up 3’ deep drifts on Super Bowl Sunday, my friends back home in Washington state were mowing their grass. At this point I don’t even remember what my lawn looks like.

I have to confess that I thought winter 2014 was an anomaly and that we wouldn’t see weather that cold again any time soon, if ever. Boy, did I get wrong number. While winter 2015 is not exactly a carbon copy of 2014, I’m not sure most of us can tell the difference. In case dealing with sub-zero wind-chills for weeks on end wasn’t torture enough, I dug into the weather records from our automated Michigan EnviroWeather network to see how the past couple of months stacked up. To keep things simple I queried the records for the past twenty Januaries and Februaries. I just include those months since we don’t have any data for this March yet and those are the months we typically get our coldest weather, though we occasionally also get sub-zero in late December.

Over the last 20 years the past two winters have been by far the coldest, and it’s not even close. Over the previous 18 years the average daily low temperature for January and February was 17.0 deg. F. In 2014 the average low was 5.9 deg. F; this year it was 5.8 deg. F.

Daily low temperatures in Jan. and Feb. of 2014 and 2015 were more than 11 degrees below the average of the previous 18 years.
Daily low temperatures in Jan. and Feb. of 2014 and 2015 were more than 11 degrees below the average of the previous 18 years.

Not only was it colder on average but we’ve had more extreme cold events in the past two years as well. Between 1996 and 2013 we averaged less than one day per year with low temperatures below -10 deg. We were below -10 deg. F on eight days this winter and nine days last winter. The bottom end of our USDA Hardiness Zone 5 is -15 deg. F. We have been below that mark five times this winter, compared to twice last year and zero times in the previous 18 years.

Over the past 20 years we rarely dipped below -10 F. We've been colder than -10 seventeen times in the past two winters.
Over the past 20 years we rarely dipped below -10 F. We’ve been colder than -10 seventeen times in the past two winters.

Obviously this data is specific to mid-Michigan, but I suspect most locations in the Midwest and Northeast will have similar stories to tell. So what does all this mean? For one, our hardiness zones are what they are for a reason. Folks that like to ‘push their zones’ (you know who you are), have gotten away with it with impunity for nearly 20 years. This winter and last were time to pay the piper.

The owner of this Cedrus deodora 'Polar winter' (zone 6) had gotten away with pushing their zone for 10 years before things came to grinding halt in 2014.
The owner of this Cedrus deodora ‘Polar winter’ (zone 6) had gotten away with pushing their zone for 10 years before things came to grinding halt in 2014.

The other take home lesson is that climate doesn’t consistently move in one direction. Even if we’re in a period of general warming, extreme events will still occur. This is important to remember as we think about planning for projected future climates. We have seen the appearance of several climate-change friendly plants lists. In some cases the authors have simply looked at projected climate zones and moved plant selections northward. The problem with this approach is tree survival is based on extremes, not on averages.