Those of you who were Twin Peaks fans will recognize the title quote. And while my topic is not quite as scary as being stalked by Bob, the fact that plant sentience continues to rear its irritating head in legitimate scientific venues makes me want to curl up in a ball and whimper. Here’s what made me cringe: “Sound Garden: Can Plants Actually Talk and Hear?”
I posted on this topic a few years ago, and I’d invite you to read it and the accompanying comments. I’m still not a fan of anthropomorphizing plants, and I still think word choices matter, especially when you are trying to educate people about science.
It’s disappointing that some scientists are deliberately using anthropomorphic language when discussing plant physiology. The cynical side of me says it’s a great way to get press coverage.
This past week I was in Alnarp, Sweden to present at the International Urban Tree Diversity Conference. Lots of interesting talks, posters and field tours. Much more to discuss than I can fit into a blog post, but if you’re interested you can read the presentation abstracts.
One of the best features of the conference is that the presenters and participants included not only arborists and urban forester but also landscape architects and urban planners. This might not sound too remarkable but these groups are not always on the same page. While urban foresters are on board with the need to diversify urban and community forests; species diversity can be at odds with uniformity, which is a key element in landscape design. For example, a common application of uniformity in design is the installation of alle’s – long, uniform monoculture plantings along a street or path.
The aesthetic appeal of an alle’ is undeniable and seemingly universal. We saw many examples in our tours in Malmo and Copenhagen, but alle’s can found almost anywhere mankind has planted trees.
The dilemma, of course, is that any monoculture planting runs the risk of catastrophic failure, especially in an era of increased global trade and potential introduction of destructive exotic pests.
Simply planting a random mix of species leads to a menagerie effect – one of these, one of those – that most eyes find unsatisfactory.
One of the challenges addressed at the conference is how to meet the design and aesthetic objectives of uniformity while still achieving diverse landscape. There are no simple solutions and like most compromises, not everyone will be completely satisfied. But at least we are getting to the point where all sides of the discussion are being heard and creative minds are melding the science and the art that will produce the desired aesthetic and diversity.
Life is full of surprises. A case in point is some recent work on our Social Media Designed Tree Establishment Study (SoMe-Ded-TrEeS). One of the objectives of the project was to determine the impact of root-ball manipulations to remove circling roots on container-grown trees. When we planted the trees (‘Bloodgood plane trees in 25 gal. containers) two years ago, we ‘shaved’ the outer roots on one-third of the trees, ‘teased’ apart the circling roots on one-third, and planted the rest as-is (‘pop and drop’ in Linda’s vernacular).
Two weeks ago our campus nursery staff dug 12 of the trees for us using their tree spade – four from each of the three groups. We then borrowed an air-spade from MSU Campus Infrastructure and Planning and we excavated the root-balls to determine the amount of new root growth into the surrounding soil. (‘We’ meaning my technician Dana Ellison and Nicole Rowley, one of our new undergraduate research assistants)
The results of the root exam were a surprise to me. Going in to this exercise my expectation was that the roots that were ‘teased’ to remove girdling roots would fare the best – and they did have visibly fewer circling roots and more new root growth than the ‘pop and drop’. But the biggest surprise was the marked improvement in rooting of the ‘shaved’ roots.
To be honest, I had some reservations about the shaving treatment. Just based on geometry alone, shaving off the bottom and outer 1” of roots around a 25 gal. tree removes over 20% of the roots; and this proportion is even greater is you consider the proportion of fine, absorbing roots. In the sampled trees, however, shaving essentially eliminated all circling roots. Even more impressive was the amount of new root growth out of the bottom of the root-balls. NOTE: In the photos below the red-dashed lines indicate the approximate dimensions of the roots when the trees were planted two years ago.
We (again meaning Dana and Nicole) trimmed all the roots that extended beyond the original root-ball and separated roots based on whether they came from the side or the bottom of the root-ball. They (the roots, not Dana and Nicole) are in the process of drying in the lab and will be weighed shortly. Based on the volume of material in the bags, however, it is clear the shaved trees will be the ‘winners’. Another example of why it pays to keep an open mind when doing research.
As spring slowly makes it appearance in the Midwest, homeowners and landscapers are likely to continue discovering damage from our record-breaking winter. While brutally cold temperatures and heavy snow loads took their toll in many areas, some of the most severe damage that occurred to landscape trees and shrubs this winter was caused by mammals.
Our long, harsh winter resulted in heavy feeding damage by deer, rabbits and voles, also called field mice. Depending on the age and type of plant and which animal was feeding on it, mammal damage can range from light pruning to death of a tree or shrub. Developing a strategy to deal with animal damage requires proper identification of the offender. Here are clues to identifying mammal damage.
Voles or field mice are small rodents that gnaw on tree and shrub stems. Voles do not hibernate and are active throughout the winter under snow, so feeding damage that occurred near ground-line when the ground was covered with snow is likely vole damage. Although they are small, voles can wreak a lot of havoc. They can easily kill small trees or branches on larger trees by girdling stems, or removing the bark around the entire circumference.
During the winter, deer feed on the ends of many types of trees and shrubs. Evergreens, especially arborvitae, are among their favorites. In most landscapes in this area, a “browse line” is a common feature on arborvitae. Eastern white pine, maples, birch, dogwoods and viburnums are also favored trees deer browse. This winter, I received reports of deer browsing on secondary species, such as Austrian pine, reflecting the severity of the winter.
Rabbits can cause damage that may resemble feeding by either voles or deer. Like deer, rabbits will chew the ends off of deciduous trees and shrubs. A close inspection of the end point will often indicate the culprit: rabbits typically leave a clean, angled bite mark, whereas deer tear or break stems, leaving a rough edge. Like voles, rabbits can also girdle stems of trees and shrubs. In winters with heavy snow cover like this one, the height of the damage can provide a clue; vole damage will extend down to the soil surface, while rabbits work above the snow-line.
Managing mammal damage
Managing mammal damage is often difficult and multiple strategies may be needed. Excluding deer with fencing can be highly effective, but is not practical in many instances. Deer repellents can also be effective, but may wear off over time or become less effective as deer become hungrier as winter wears on. Around our place, our dogs to a good job of keeping deer and rabbits at bay, but of course require their own care and feeding.
Reducing weeds and ground cover can help to reduce damage by rodents by eliminating cover from their predators. Trapping may be effective for controlling rabbits, but is usually not practical for voles. Baiting can be used for voles, though care must be taken to avoid poisoning non-target animals. In some situations, erecting raptor perches can also be helpful in keeping rodent populations down.
Ridding an ecosystem of invasive plants is never easy. We can bring in goats to munch on offending plants or force armies of schoolchildren into slavery to pull them out; but, in all likelihood the sneaky little devils (the invasive plants, not the schoolkids) will be re-sprouting and back with a vengeance before we can turn around. For many invasive plant infestations the most practical long-term solution is chemical control – in other words, herbicides. Of course, herbicides have their issues such as drift and potential impacts on non-target plants. And what do you do when you want to get rid of invasive plants in a remote, sensitive ecosystem with limited access? Enter Herbicide Ballistic Technology (HBT). The HBT system uses the same technology as a recreational paint-ball gun but instead of filling the projectiles with paint, the balls are filled with triclopyr, which is commonly used in homeowner products for brush and poison ivy control.
Dr. James Leary at the University of Hawaii has been exploring the use of HBT to control invasive plants in various ecosystems in Hawaii. Most of the time Dr. Leary and his colleague use the standard paintball HBT system, but for the big jobs they call in the heavy artillery – literally. Dr. Leary recently presented a seminar here at MSU on work he and his team have conducted in conjunction with the Maui Invasive Species commission to eliminate populations of Miconia calvacens, one of the most problematic invasive trees in Hawaii. According to the seminar abstract, Dr. Leary reports “Our best utility for HBT deployment on a Hughes 500D helicopter platform featuring real-time capabilities in target elimination. …we have conducted 17 tactical search and destroy mission covering a total net area of 3,888 ha and eliminating 7,463 Miconia targets.”
Clearly the war on invasive has been raised to a different level
One of the most obvious impacts of this winter’s winter is rapidly becoming apparent in Michigan and other parts of the Midwest: winter burn on conifers. The primary symptom of winter burn is needle browning, especially on evergreen conifers in exposed locations. Needles may be damaged by extreme cold or the browning may be associated with winter desiccation as needles lose moisture during brief warm-ups. Winter burn is one of those situations that draws a lot of attention because it can look devastating; yet it often has relatively little long-term impact on plants.
The key to the lasting effects of winter damage on evergreens is the extent to which buds are damaged.
With a little practice it is relatively easy to determine the state of conifers buds. With your thumb and forefinger pull the bud scales from the top of the bud. With a good hand lens or dissecting scope you will be able to see the bud primordia. On healthy buds this will be bright green; on damaged buds the primordia with be brown or black.
I recently examined buds from Douglas-fir trees on campus that had severe needle browning this winter. In several cases, trees had severe needle browning but the buds were fine. These trees will likely put on a normal growth flush this spring and in a year or two it may be difficult to tell they were ever damaged – assuming we don’t have a repeat of this winter’s severe weather.
On some other trees, however, the buds had been killed by this winter extreme cold. This doesn’t mean these trees are dead – they may still form adventitious buds along the stems – but it will certainly set them back and will likely impact their form and symmetry.
Bert’s done some nice posts on his SOcialME DesignED TREE transplant Study (or SOME DED TREES). I’m going to add to the discussion with a new addition to my Preventing Optimization Of Roots DecrEAseD TREE Survival (or POOR DEAD TREES) series.
It took a while, but the prediction I made in 2010 has come true. You’ll have to look at the link to see the whole story, but the bottom line is that this tree lasted only 7 years before succumbing to poor planting practices.
Here is the tree when it was planted in 2007. Note the lack of root flare (planted too deep) but the very obvious presence of orange nylon twine around the roots and the trunk.
Here it is again in 2010. Note the dieback at the top and overall chlorosis.
And here it was yesterday.
Yes, it’s dead – dead and gone. I’m not sure exactly when it was removed, but it lasted less than 7 years. Conifers have lifespans of decades or centuries. There was no excuse for this poor installation, though I keep getting the argument from landscape installers that it costs too much to do it right (i.e., to remove the twine and burlap, if not the clay itself). Keep in mind that warranties only last for a year, so the property owner gets to eat the replacement cost caused by crappy installation practices.
We GP’s may continue to disagree about how much rootballs should be disturbed when planting, but I know that none of us would agree that planting B&B trees intact is a good idea.
I’m sorry I’ve been so quiet, but I am not feeling SPRING. Here in the Blue Ridge of Virginia (Zone 6), March is averaging 10 F below average. Snow and ice is piled up on the north side of buildings. My Herbaceous Landscape Plants class is not impressed by the inch-tall Mertensia and the fact that the only thing we can call a cool-season annual (pansies/violas) is brown mush. All the delightful Zone 7 things I’ve been pushing on people for several years here – er, whoops. This is as far north as I’ve ever lived (please don’t mock me Bert). I’m tired of bales of laundry. Flannel sheets, corduroy, fleece…I am NOT good with winter. I admit I am at my best with only one layer on. And if one more person says “at least we’ll have fewer ticks”…
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.
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.