Bert Cregg

Going off half-cocked

The good news about being a landscape extension specialist is you get to comment on a variety of landscape tree problems. The bad news? You get to comment on a variety of landscape tree problems. In an average week I probably get 10-15 tree-related calls or e-mails from homeowners, landscapers, growers, extension educators, lawyers, newspapers, and on and on. Sometimes the problem is routine and obvious like tar spot on maples; “I have these spots that look like tar on my maple leaves…” Sometimes the problem looks routine and turns into something else entirely different like the Imprelis herbicide debacle. With the number if problems I respond to, invariable I sometimes end up shooting from the hip – and miss the mark.

Red maple with sparse canopy (right foreground). Maple in left-center of picture across the road was planted at the same time.

A few weeks back I noticed some red maples on campus that were struggling as they were starting to leaf out. There were planted about three years ago following a road-widening project. They are located on a tough site between a parking lot and a busy 4-lane road. My immediate diagnosis was they were weakened due to the aftereffects of last year’s sever heat and drought. I even included a photo of them in an article I did for our on-line extension news. Then this morning I happened to talk to a friend from our campus landscape services. “Boy, those maples sure took a beating from the drought last year”, I volunteered. My Landscape services friend replied, “Well, that and we hit them with Shortstop last year…” Uh oh, now the conversation was going in a different direction. Shortstop is a plant growth retardant, the active ingredient is paclobutrazol, which inhibits GA synthesis in plants and is being widely used by arborists to reduce the need for tree pruning. In this case it worked a little too well and the trees ended up being stunted.

Leaves of paclobutrazol-treat maple (left); untreated leaves on right.

In my defense, I was partly right. Under normal weather patterns paclobutrazol applied at the labeled rates (as was done here) would have reduced shoot growth and leaf growth but clearly the drought exaggerated the effect. So, another lesson learned (actually re-learned) never assume anything about trees until you talk to the people who actually take care of them.

Label GMO foods? Sure, why not?

Lots of coverage in the mainstream media these days over various initiatives to label GMO foods. I think GMO foods should be labeled; but not for the reasons you might think.

My personal opinion on GMO foods is that their benefits outweigh the potential downsides. I think GMO foods should be labeled to make the public aware of how much of our food supply depends on GMO’s and the cost of not using GMO’s. Obviously this will raise some social justice issues since wealthy people will have more opportunity to opt out of buying non-GMO products than the poor but it’s the same problem we have with organic already and it doesn’t seem to cause much of a stir. My hope is that once GMO products are labeled we could get to the point where the main discussion on GMO’s focuses on the rational and scientific questions, not the irrational and emotional. This weekend our Sunday paper included a quote from a local anti-GMO activist who tried to link the rise in obesity to increased use of GMO’s. How about we’ve become too sedentary and we’re eating too much, period? Or this from the “Health Ranger” Mike Adams: “Roundup herbicide devastates soils, rendering them contaminated and unable to produce healthy crops using traditional (or organic) farming methods. Once a farm plot is destroyed with Roundup, that farmer is forever enslaved to a chemical-based farming protocol.” Hmmm… last time I checked farms could be certified organic after three years without synthetic chemicals.

Which is not to say I don’t have concerns about GMO’s; there are issues with any technology. The largest questions I see, and the ones that are most difficult to answer, relate to unintended consequences. One of the biggest selling points of Round-up ready technology, for example, is that it enables farmers to manage weeds with glyphosate, a relatively safe product in the world of industrial-strength herbicides, in order to reduce tillage and maintain crop productivity. But as farmers use more and more glyphosate, they are also selecting for Round-up resistant weeds. How long until glyphosate is no longer effective? Difficult to predict, but glyphosate resistance has already evolved in many weeds.

On the other side of the equation, the world’s population is projected to exceed 9 billion by 2050, with a disproportionate increase in the least developed countries. As the need for food increases, land and water resources will become more limited and catastrophic droughts are likely to increase. While it is easy to demonize industrial agriculture, it’s difficult to envision feeding ourselves and the world without the technology it has developed.

The Canary in the Coal Mine

Three weekends ago marked a milestone of sorts as mean daily CO2 levels at the National Oceanic and Atmospheric Administration observatory at Mauna Loa, Hawaii topped 400 ppm for the first time ever. Rising levels of CO2 and other greenhouse gases could result in significant increases in temperature in the Upper Midwest over the next century. When we think about trees in cities the scenario is even worse since not only will urban trees have to deal with overall temperature increases but they must also contend with urban heat island effects, which can add another 8 deg. C or more of heat load. Because of this ‘one-two punch’ of global climate change and urban heat island effect, I often refer to urban trees as the proverbial ‘canary in the coal mine’ with respect to climate change since they will likely be impacted sooner and more dramatically than trees in woodlands.

In general, organisms have three options to deal with a change in their environment: They can migrate, they can adapt, or they can acclimate. Since trees are sessile organisms, they can’t pick up and move so migration is out. Current predictions are that climate will change faster than trees can evolve so natural selection and adaptation will be limited. Which leaves us with acclimation, or the ability of a tree to adjust its physiology and morphology to its environment. A common example of an acclimation response is the development of sun and shade leaves on the same tree. Another example of an acclimation response is an increase in the optimum temperature for photosynthesis in response to exposure to increasing temperatures. In theory, trees that have a greater capacity to adjust their physiology to increasing temperature will be better suited for future, presumably warmer climates.

We are currently testing this idea in a two-part study. In part one we are growing trees from several shade tree cultivars in greenhouses under three temperature regimes; ambient temperature, ambient + 5 deg. C, and ambient +10 deg. C. In part two of the project we planted trees of the same cultivars in two sites in Detroit in cooperation with the Greening of Detroit. The Greening of Detroit is community based non-profit organization that assists neighborhood groups, churches and schools in their efforts to improve the ecosystem in Detroit through tree planting projects, environmental education, urban agriculture, open space reclamation, vacant land management, and workforce development programs.

Many hands make light work. Greening of Detroit volunteers plant trees along a street median.

With the help of Greening staff and about 90 Greening volunteers, we recently planted 160 shade trees in downtown Detroit. One site of the study is in a park, representing a relatively mild micro-climate; while the other site is along a street median surrounding by asphalt with a much higher reflected heat load. Both sites with be instrumented with environmental sensors and we will compare growth over time as well as physiological responses such as the response of photosynthesis to temperature. The long-term goal is to identify traits that will be most important to guide future selections of trees of urban and community forestry under changing climatic conditions.

Research Technician Dana Ellison (left) and Research Aide Aiman Shahpurwala finish planting a park tree.

A pick ax as a planting tool? Dana shows how it’s done in Detroit.

Should back-fill be amended? My usual answer is ‘no’, but then again it depends what your back-fill looks like…

Sizing things up. Aiman and Dana collect initial data on trees after planting.

Rubbing salt into wounds

Last week I posted about some horticultural disasters I witnessed in the Czech Republic. This week the chamber of horrors is little closer to home; virtually in my back yard to be specific. Our property backs up to US 127, the main North-South through route in our area. It’s a limited access highway with a posted speed of 70 mph, which means an average speed of 82.7 mph. It also means the road is regularly salted whenever it snows during the winter. As a result, some plants along the highway really take a beating, sometimes with some interesting results.

On Friday I received an email from Susan Gruber, our Undergraduate Advisor, who also commutes on US 127. “Hey Bert, Have you seen the pear trees on the east side of NB 127 just south of the Round Lake Road (and Price Rd) exits? Street side fried, shows up great with flowers on the other side. Also same trees planted at the same time doing great by the ramps, farther from the road, slower traffic, some up on the berms etc. Make great GP fodder, but I didn’t have a decent camera or the guts to pull over and do phone photos in rush hour.”

Unaffected pears upslope and away from salt exposure

Indeed I had seen the trees. As Susan noted, the sides of the trees facing the highway were fried, the opposite sides were in full bloom. I got a few photos over the weekend but the effect was a little less striking than earlier in the week when the trees had blooms but hadn’t begun the leaf out.

Pear trees in the line of fire

The planting illustrates a classic example of wrong tree-wrong place. Interestingly there are several crabapples that were installed as part of the same planting project that seem to be doing well. Selecting trees for exposure to deicing salt is a dicey proposition since, like this example, most of our information is anecdotal. Where the effects of deicing salt on plants have been systematically examined, the studies may focus on only soil exposure or only aerial deposition; whereas trees in the real world get it with both barrels.

Eastern white pine after one winter at a rest area along I-96 east of Lansing. An ideal proving ground for salt tolerant plants.

Ironically a colleague of mine in our department and I put together a proposal several years ago for our state Department of Transportation (MDOT) to identify salt tolerant plants for roadside plantings. Our plan was to install a series of replicated plantings of perennials (trees, shrubs, herbaceous perennials) at highway rest areas throughout the state. We would then correlate plant performance with degree salt exposure and identify plants that could survive, grow and maintain their aesthetic value under the highest salt loads. Initial discussions were positive until the proposal worked its way up the chain of command. Finally it was determined – I am not making this up – that MDOT could not participate in a project on indentifying plants that were tolerant of deicing salts because that means they would have to admit that salt was causing a problem. OK; just don’t tell the trees on US 127…

In our studies we rate plants on a scale of 1 (alive) to 5 (dead). These are class 4 (wish they were dead…)

Random acts of horticultural violence

I’ve been traveling in Europe the past few days working on a project with some colleagues in the Czech Republic. While we typically think of our friends in Europe as being more progressive and cultured than us, it appears there are still a few areas where they have a ways to go – such as banning smoking from restaurants and bars – and in learning about the art and science of Arboriculture. (And before the hate mail from Europe starts pouring in; yes, I realize we can find plenty of scenes like this in the US – just hoped I’d find better on this side of the pond).

I’m not a big Forsythia fan, but really…?

Not sure what the desired outcome is here.

This is a black locust near Prague castle. Black locust, which is native to North America, was introduced to Europe for forestry planting in the 19^th Century. The trees were extremely well adapted and have become invasive in many parts of Europe, out-competing native trees and suppressing the development of understory plants. This particular specimen is one of the oldest in the Czech Republic, which presumably is the reason it has been allowed to linger on. A good example of when a tree’s quality of life has run its course. It truly pained me to look at this tree. And, of course, in the U.S. the tree would probably have been long gone due to liability concerns.

The tree is mostly hollow and was once cabled together. The cables were removed after the tree lost its tops in a storm 20 years ago.

It appears that the tree’s principle function these days is feeding woodpeckers.

OK, in the interest of international diplomacy, something Europeans get right is pollarding. In the U.S. what is passed off as pollarding is usually just topping. But when it’s done right (in this case with horseschestnut) and in the right setting (Prague Royal Gardens) it can create a striking effect.

Spring fever: Conifer style

We finally got a reprieve from our wet, cold weather. Just in time for the annual inspection of the conifer troops at the Harper Collection of Dwarf and Unusual Conifers at MSU’s Hidden Lake Gardens. One of the interesting things about making repeated trips to a conifer collection like this is that different conifers stand out each time. Whether due to lighting, background foliage, your mood, whatever; it seems like there are different stars each time.

Here are some of today’s standouts.

Pinus contorta var. latifolia ‘Chief Joseph’
‘Chief Joseph’ lodgepole pine. Discovered in the wild near Joseph, Oregon where Chief Joseph, leader of the Nez Pierce once lived.

Abies concolor ‘Blue cloak’
‘Blue cloak’ concolor fir (white fir for people living on the West coast). One of the most intense blue forms of color fir – rivals virtually any Colorado blue spruce.

Sciadopitys verticillata ‘Joe Kozy’
‘Joe Kozy’ Japanese umbrella pine. Sciadopitys is one of the most primitive forms of conifers with fossils dating back over 230 million years. This cultivar was selected for its fastigiate growth by Sidney Waxman at the University of Connecticut.

And, of course, they always look great when you put them together. For more info on these and other conifers check out the American Conifer Society Conifer database.

It’s raining, it’s pouring, it’s a good time for a site assessment…

April is turning out to be a soggy month for most of Michigan and our surrounding states. While most homeowners are inclined to hunker down indoors and keep an eye on their sump pumps on these dark, dreary days; our current run of wet weather is a good opportunity to take a stroll around your property and make some notes. In particular, note any areas where water is accumulating.

Poor drainage is one of the most common sites factors that limit landscape tree and shrub survival and growth. Sites that retain water for more than a day or too after rains stop are especially problematic. The challenge with wet areas is we usually wait to plant trees and shrubs until things are high and dry and it’s easy to forget where the wet spots are.

There are two primary strategies for establishing healthy trees and shrubs in flood-prone spots. First, determine if the problem can be corrected. In some cases homeowners may be able to re-direct water flow from downspouts or other sources to keep water form accumulating in one spot. Again, these kinds of problems are easiest to spot if you go out when it’s raining. Re-grading the area or installing drain tiles are other options but these are usually require skills and equipment beyond the average do-it-yourselfer.

If correcting the drainage issue is not an option, the second strategy is to plant trees or shrubs that are tolerant of flooding. Plants vary widely in their tolerance of soil flooding and, not surprisingly, trees and shrubs that grow naturally along riverbanks and other low areas are usually the most tolerant.

This low spot in my yard was a good site for a Baldcypress

There are numerous resources on flood tolerant trees and shrubs on the web. Two of the better resources are from the Morton Arboretum and from Cornell University. Please note the Cornell guide is a large (>6 MB) .pdf file.

These Michigan holly (Ilex verticullata) I planted a couple of years ago a doing fine even though they are periodically flooded each spring.

Wet areas on your property do not have to be a ‘dead zone’, but establishing trees and shrubs in low laying areas takes some planning. The first step in the process is assessing your site and identifying the problem areas. The best way to do this is to put on a raincoat and take a walk in the rain.

Protecting plants from frost

What a difference a year makes. This time last year our growing degree day accumulations were nearly a month ahead of normal and we had already experienced temperatures in the 80’s, with more than a week straight of 70 + deg. temperatures. This year, of course, is a different story. But spring will come eventually. As trees and shrubs begin to leaf out or we get antsy and begin to plant annuals, we need to be prepared for late frosts.

Searching on the internet for ‘plant frost protection’ will yield a wide array of strategies for reducing frost damage. Some strategies such as frost irrigation or wind turbines are mainly geared to commercial horticultural operations such as orchards or nurseries. Other techniques such as a various spray-on products usually provide only a few degrees of protection or are variable in their effectiveness. For homeowners, the most effective technique is the ‘old tried and true’; covering plants loosely with a bed sheet or similar lightweight fabric.

Photo: gardeingadvice.net

When covering plants for frost protection it is important to remember the basic principle at work here. Late frosts typically occur on clear nights. That’s because the lack of cloud cover allows heat from the earth to re-radiate into outer space. By draping a sheet or other lightweight covering over plants, the radiant heat from the ground is trapped, preventing plants from freezing.

I bring this up because I have seen several forms of ‘plant protection bags’ currently on the market. In terms of protection from late frosts, these are more likely to turn out to be plant body bags. Some of these bags are designed to gather at the base; sort of like putting on a coat. This is another example where making analogies between human function and plant function falls apart.

Remember, the point of covering plants is to trap the earth’s heat, not the plant’s heat.

More importantly, frost cover protection needs to be removed each morning as soon as temperatures begin to warm. Late frosts usually occur on clear nights, which means the next morning is typically bright and sunny. Under direct sun, temperatures under frost covers can build quickly, resulting in heat damage to new growth. Yes, going out to drape sheets over plants each evening and then removing them the next morning is a pain but like so many things in life, the tried and true is the safest bet.

WARNING: This post contains graphic content

As many of you know, numerous homeowners and golf courses in the Midwest experienced substantial damage to trees, especially conifers as a result of application of Imprelis, a new turf herbicide that was released by DuPont in fall 2010. If you do a google image search for ‘Imprelis’ you can see lots of photos of the typical damage we observed in summer 2011, when most Imprelis damage became apparent. The usual symptom of Imprelis exposure were brown, twisted and stunted shoots or trees killed outright.

White pine killed by Imprelis – July 2011. Photo: Bert Cregg

Shoot damage – July 2011. Photo: Bert Cregg

Today, however, I received some images from an Extension Educator in southwest Michigan that turned my stomach. So what happens when trees that weren’t killed by Imprelis try to resume growth? The results are not for the feint of heart.

‘Club-like’ shoots – March 2013. Photo: Beth Clawson.

‘Tumor-like’ growths at the ends of shoots – March 2013. Photo: Beth Clawson.

Imprelis damaged shoot cross section – March 2013. Photo: Beth Clawson.

Long winter proves that climate change is a hoax

Just looked at the forecast for the week – Thursday’s forecast high temperature is 32 deg. F. This is a far cry from last year’s record-shattering 86 on the same date. Clearly all this blabbering about climate change is just a bunch of hysterical nonsense.

As sportscaster Lee Corso would say, “Not so fast, my friend…” While winter 2013 can’t compete with winter 2012 in terms of record-breaking warmth, this winter has continued a trend which may have profound implications for landscape and garden plant selections.

As you’ll recall, last winter saw the release of a new USDA Hardiness zone map which indicated that most areas of the US had warmed by at least one-half hardiness zone (5 deg. F) since the previous map was produced 22 years earlier. Hardiness zones are based on average minimum temperatures; in other words, what’s the coldest temperature you’re likely to see in a given winter. As it turns out, minimum temperatures have been warming faster than overall average temperatures. So much so, in fact, that one researcher declared the brand new hardiness map dead on arrival. Nir Krakauer at City College in New York noted that if we look at trends, rather than averages, many areas of the US are already another half a zone warmer than the new USDA map.

Minimum winter temperatures are warming at a much faster rate that average temperatures

Last week I gave a presentation at the Minnesota Shade Tree Shortcourse and pulled together some cold hardiness data for the Twin cities. According to the new USDA map, Minneapolis-St. Paul is now zone 4b (-25 to -20 deg. F). One way to think of this over a long enough time-span, about 1/3rd of their winters should reach a low in that range, 1/3rd should be slightly warmer, and 1/3^rd should be slightly colder.

The new USDA map indicates the Twin cities are in zone 4b

I pulled out the winter weather records for Minneapolis-St. Paul since 2000, including winter 2013. In the past 14 winters temperatures in the Twin cities have dipped to their hardiness zone level exactly once, 2004. All other minimum temps were at least 5 deg. F warmer.

Annual minimum temperatures at Minneapolis-St. Paul airport (MSP) have reached zone 4b levels only once since 2000.

Obviously a 14 year record is not sufficient to build a hardiness map. Nevertheless, if someone tries to use this winter as proof that climate change is hoax; just remember, minimum winter temperatures – the temperatures that serve as a primary limit of which plants can grow where – tell a different story.