Uncategorized – Page 48 – The Garden Professors™

Who you gonna call?

As I noted last week, this has been a long winter in Michigan – OK, Jeff, no chortling from the frozen tundra of Minnesota… Most gardeners in this area have only been able to do their spring yard and garden clean-ups in fits and starts as the weather allows. We’re finally warming up a bit this week but now strong storms are in the forecast. One of the things gardeners will want to do is to size up any winter damage that has occurred since they put things to bed last fall. Although our winter was long, it was otherwise unremarkable with few temperature extremes – low or high – that would likely cause problems. In fact, aside from some heavy snow in February, the winter of 2010-11 was probably the closest thing we’ve had to a ‘normal’ winter in the 11 years I’ve lived in Michigan. Nevertheless, we will still be taking numerous extension calls on what we would consider ‘typical’ winter damage to trees and shrubs.

In this neighborhood not too far from my house, deer have declared open season on arborvitae.

One of the biggest issues we face is wildlife damage. The two biggest sources of problems are small mammals and deer. Small mammals such as mice, rabbits, squirrels and voles cause damage mainly by gnawing on trunks and branches. Despite their small size, these animals can kill trees by removing bark and underlying tissue around the circumference of a tree trunk, a process referred to as ‘girdling’. If a large portion of trunk circumference has been girdled, trees are unable to move energy reserves between roots and shoots, and will eventually die. Deer can cause extensive damage to trees and shrubs due to feeding and also through rubbing their antlers. Deer feeding is often indicated by a ‘browse line’ based on how high deer can reach. Rub damage from deer antlers can cause major deformation to trunks and can even kill trees by girdling. I was in a new subdivision in the East Lansing area this weekend and well over half of the trees on the tree lawns will need to be replaced due to extensive deer rub damage.

At least half of the trees in this entire subdivision will need to be replaced due to deer-rub damage.

Dealing with wildlife damage is a complex issue and varies with local conditions and wildlife pressure. Fortunately, wildlife experts from several universities (Cornell, Clemson, Nebraska, Utah State) have organized the Internet Center for Wildlife Damage Management. http://icwdm.org/ This site is one of the best resources I have run across for assessing and dealing with wildlife damage issues. If you’re in a position where you have to deal with wildlife damage or advise clients about damage, this is a useful site to add to your bookmarks.

Invasive plants, politics and science

I’ve had a hectic week (taxes! financial aid!) and haven’t had a chance to think about posting. Fortunately, yet another colleague just sent me an interesting link that’s worth sharing and discussing.

For those of you who aren’t familiar with how Master Gardener programs work, they are built on volunteers who receive training in garden-related sciences and then contribute a significant number of hours to outreach education. Many MGs work in plant clinics, and others volunteer in public gardens. Regardless of where they spend their volunteer hours, they are always representing their sponsoring university and therefore dispense advice and follow practices based on the best available science.

This will help explain why the Master Gardeners who volunteered at the Racine Zoo felt they had to resign their volunteer positions.

(Note that the zoo is losing out on 1300+ hours/year of donated garden upkeep, but the zoo president and CEO is confident that the zoo staff can pick that up. Wonder if he’ll be out there weeding and watering?)

Interesting and useful web site about invasive insect pests

Just heard about this from a colleague. This website has a link to a great image gallery of exotic insect pests. Though it’s primarily geared towards forest pests, the urban forest is just as susceptible.

Invasion of the killer earthworms

It sounds like a B-grade horror movie. Millions of earthworms, moving silently beneath soil, wreaking havoc until the entire planet is uninhabitable. Sound a little far-fetched? Not to ecologists that study northern hardwood forests. While most of us grew up thinking earthworms were ubiquitous, turns out they are not native in parts of North America that were covered with ice during the last glacial period. Most of us also grew up thinking that earthworms where the good guys/girls (they’re hermaphroditic), churning up compacted soil and leaving nutrient-rich castings behind. In many northern hardwood forests, however, exotic earthworms, have become invasive and ecologists believe they are having profound effect on ecosystems.

I have to admit I hadn’t paid that much attention to the invasive earthworm issue but I attended a seminar last week by Dr. Lee Frelich, Director of the Center for Forest Ecology at the University of Minnesota. Dr. Frelich’s seminar touched on several areas of research, almost all of it extremely depressing, related to climate change and invasive species. He and his colleagues have documented significant changes in soil ecosystem processes and plant succession associated with increasing populations of earthworms. Nightcrawlers, in particular, cause a lot of problems because they consume fresh leaf litter causing it to decompose at a much faster rate compared to un-invaded ecosystems. The net result of these soil changes is that few trees or shrubs can reproduce in the understory. Over time this may lead to a very different looking forest than exists there today.

Of course, we may end up with a very different forest in any event, given some of the climate change scenarios Dr. Frelich presented. One worst-case model predicted the climate of the Boundary Waters area of Minnesota would resemble that of present-day Oklahoma City by the end of the century. But I try not to worry; I figure by that point I’ll be food for the earthworms anyway.

For more info on the earthworms that ate Minnesota, check out these links, if you dare…

http://www.scientificamerican.com/article.cfm?id=invasive-earthworms-denude-forests

http://www.dnr.state.mn.us/invasives/terrestrialanimals/earthworms/index.html

California Flower, Food and Garden Show

I’m giving two talks at the California Flower, Food and Garden Show in Sacramento today and tomorrow: details are linked here. It would be great to meet some of our California readers in person if you plan on being there.

I’ll try to take some photos and share my thoughts about the show on upcoming posts. Maybe I’ll even find my Friday quiz topic lurking there!

Rain barrels

A few weeks ago one of our readers, landscape architect Owen Dell, sent me a link to his blog where he takes on rain barrels. It’s a great analysis of the (im)practicalities of rain barrels and it got me to wondering how many of our readers (and my GP colleagues) use these as supplemental sources of irrigation water?

I have two in our back yard that were made from old olive oil containers retrofitted for collecting and dispensing water. They’re hooked together so that when one fills, the rain is diverted to the second.

We use this water pretty much for watering container plants, especially those on our south-facing front porch that require watering every other day during the summer. The barrels each hold 55 gallons and are always full during the winter and spring. We drain them almost dry over the summer, but even a brief rain results in several gallons collected.

So I think they’re a pretty good deal, since we use relatively little water from the hose to keep our container plants happy. But Owen brings up some valid points in his analysis, as do commenters on his blog.

What do you all think?

Is local always better?

As those that have followed the blog for awhile are aware, among my pet peeves are some of the naïve statements that are repeated ad nauseam by proponents of native plants for landscaping. You know the usual litany: natives don’t need water, don’t need fertilizer, resistant to insects, resistant to diseases, yada, yada… According to the dogma, native plants possess these traits because they’ve evolved here and they belong here. I hasten to point out; I have nothing against natives and think we ought to plant more of them whenever they are an appropriate choice. The problem, of course, with the typical native company line is that these statements are so obviously nonsensical they undermine the credibility of native plant advocates. Adaptations to resist environmental stress, for example, are a function natural selection and evolution. There are lots of droughty environments in the world; why should we assume that only local plants will be adapted to drought? Then there is the obvious problem of disturbed environments. Why should we assume that trees that have evolved in native woodlands will be good street trees? In fact, often they’re not.

Torryea taxifolia

But a new and potentially contentious argument is emerging in the ‘Is native better?’ discussion: Assisted migration. The basic premise of assisted migration (also referred to as assisted colonization) is that climate is changing faster than many organisms, especially long-lived organisms like trees, can evolve. Therefore to prevent species extinctions we should pro-actively move species (typically northward in the Northern hemisphere) so they will be in a better place as the world gets warmer. Sound far-fetched? Some of this is already occurring. In Florida a group called the Torreya Guardians has already taken it upon themselves to establish populations of a threatened conifer, Torreya taxifolia, in the southern Appalachians, outside of its native range in the panhandle of Florida. http://www.torreyaguardians.org/ In British Columbia, the provincial forest service is beginning to incorporate climate change scenarios into its tree improvement and development plans; trying to identify seed sources and species adapted to climates predicted throughout the 21^st century.http://www.msnbc.msn.com/id/32012170/ns/us_news-environment/

Is local better? Foresters often see significant growth gains by moving seed sources northward. Will climate change increase this effect?

Clearly assisted migration is a controversial topic fraught with all kinds of uncertainties. Is climate really changing? How fast will it change? What about unintended consequences? Could the assisted species out-compete a local species that would’ve been OK otherwise? And then there are those who might wonder aloud about the hypocrisy of embracing species movements when they’re done by conservation biologists but not by horticulturists.

Cold enough for ya?

Like many people we spent the past couple days digging out from the massive snowstorm that swept across a large swath of the country. This was definitely a made-for-TV-weather event as national and local TV weatherfolks took up their positions and gave us breathless live-remotes of the “Blizzard of 2011”.

40 mph wind + 1 little crack = a barn full of snow.

Almost as predictable as video footage of snow-ploughs on the streets and locals snow-blowing sidewalks; climate change skeptics are using the recent round of winter weather as proof that global warming is a hoax and that there’s really nothing to worry about except the economics of ‘cap and trade’. Just google “climate change skeptics blizzard” and you’ll get the idea.

Bob and Quincy were unfazed by the sub-zero wind-chills.

The problem, of course, is that climate patterns don’t move in a strictly linear trajectory and looking at one extreme event doesn’t prove anything one way or the other. Even looking a few years time sequence may not present the full picture. Deroy Murdock used the illustration below to argue in the National Review Online that there is no link between rising CO2 and increasing temperatures.

But looking at a broader timescale tells a different story. While there are year to year fluctuations a clearer association between rising CO2 and global temperature begins to emerge.

The figure above was taken from an article by Stamhoff et al. 2007, “Recent Climate Observations Compared to Projections” (Science 316 (4): 709). The dashed lines represent the ranges predicted by a major climate model starting in 1990 – the solid line represents what actually happened. As shown in the figure, climate models have been fairly accurate overall and, if anything, have been conservative in predicting climate change; especially with regard to changes in sea level.

So where am I going with this? There are certainly enough climate change debate/Al Gore bashing blogs out there to go around and I don’t want to devolve entirely into that debate, but the simplistic ‘exception proves the rule’ mentality of the skeptics gets a little tiresome. I remember hearing my first talk on global warming at a forest biology conference in the mid-1980’s. The main point that stuck with me then was that increasing global CO2 would not necessarily result in warming every year but that we would see an increase in the frequency and severity of extreme climatic events; droughts, hurricanes, floods, and yes, even blizzards. Even some of the earliest discussions on climate change in the early 1980’s (e.g., Manabe and Stoufer 1980) recognized complex feedbacks in the global climate system that would result in some regions getting wetter while others suffered drought. So while the skeptics may use this weeks’ blizzard as evidence against climate change, increasing frequency of severe weather actually argues for it.

A few other climate facts to ponder:

-Global CO2 is increasing and continues to increase (see top panel in figure above).

– Globally, 12 of the 13 warmest years on record have occurred since 1995.

-Intensity of hurricanes and cyclones is increasing (Webster et al., 2005). While Fox and Friends were happily using the Blizzard of 2011 to debunk climate change; did they notice the most powerful cyclone on record was slamming into Australia?

-Frequency and severity of droughts is increasing worldwide (Burke and Brown, 2006).

-Glaciers are disappearing. If you want to go to Glacier National Park and actually see a glacier, you need to hurry. In 1850 there were 150 glaciers in the park. Today there are 25 and they will likely be gone in 10 years.

Warning: This blog may be hazardous to your health

Following up on Jeff’s post last week regarding blue spruce. Jeff noted, and several posters agreed, that even though blue spruce will eventually have a host of pest problems, for the first 10 years or so it’s a darn good looking landscape conifer. Jeff went on to draw the analogy that choosing a blue spruce is like choosing sexy sports car or gas guzzler over a boring, high MPG sedan. To a certain extent the libertarian in me agrees. If I want to plant a blue spruce in my Michigan backyard or buy a Nissan Titan to commute back and forth to work , by Gawd, that’s nobody’s business but my own. Of course the difference in these situations is that I have EPA reporting to tell me the Titan only gets 12 MPG in the city; for the spruce, people like Jeff, me, and our highly intelligent readers know what we’re getting into from experience and training. But what about the public at large? Maybe what we need are government warning labels for plants. We have them for cigarettes: “Warning: Smoking Causes Lung Cancer, Heart Disease, Emphysema, And May Complicate Pregnancy”, though the European warning, “Smoking kills” is more direct and to the point. We also have warnings for side effects of prescription medications; “may cause nausea, vomiting, headache, hearing loss, oily discharge, an erection lasing four hours, and thoughts of suicide”. Think I’ll take my chances with the disease, thank you.

So what kind of labels do plants need?

Blue spruce: Warning this plant will look great in your yard for 10 years and then fall apart when it becomes a magnet for gall adelgid and loses half its limbs to cyctospora.

Eastern white pine: Caution: This little guy looks like a cute little Christmas right now but in 10 years it can devour your house.

Silver maple: Warning: Don’t blame us when this tree comes crashing though your house during windstorm.

Sweetgum: Caution: Be sure to retain a good attorney for when your neighbors start tripping over gumballs on the sidewalk.

That’s a start. What plants do you think need warning labels?

A comment about home remedies from Catherine Daniels

In case you didn’t see yesterday’s comment that was added to Jeff Gillman’s January 6 post on home remedies, I’ve posted it here. Dr. Catherine Daniels is WSU’s pesticide coordinator:

I’ve enjoyed reading the science-based information on your site. Keep up the good work. As regards home remedies, that is slippery slope, both legally and morally. Having a written definition of what you will or will not accept is helpful, especially if done in advance. Then you can be sure of being consistent and deliberate at least. There are both state and federal laws regarding pesticides, and state laws do vary. The most important thing is to know your state’s interpretation of those laws and to be mindful that with a blog you may be talking to people in state’s where laws are interpreted differently. I mention that for your legal protection. For example, in Washington State, if you talk to a user group (such as the public), and discuss the ways to use a material as a pesticide, it becomes a de facto pesticide recommendation. A legally-liable recommendation. When a researcher publishes information in a journal it’s not directed at a user audience so is not considered a recommendation by the author. If you take it to the public, at least here, it becomes a recommendation you made, unless you insert certain disclaimers. It’s always attractive to try and “help” the public find some easier, faster, cheaper solution to a pest problem. With pesticides and the public, you offer a better service directing them to a tested material which is registered and has a consistent concentration from batch to batch. Having personal safety and storage instructions is important…things that are missing in make-it-yourself squirt bottle solutions. Home remedies encourage people to think that the solution is “safe” (for people, not pests) because it’s made out of everyday ingredients. But as we know, the dose makes the poison. Nicotine is a nerve poison which you wouldn’t want a child to come into contact with accidentally because the squirt bottle wasn’t labelled or put in a safe place. I agree that our role is to educate, not police household cupboards or public pesticide use patterns. But by the same token, because we (educators)are trained to look at the big picture, there are good reasons to consider sticking to a label. Thanks for the opportunity to comment.