It was a dark and stormy night

It-Was-A-Dark-and-Stormy-Night-from-Snoopy-e1375218659590 chicago nowcom

A wild and wooly night for many of us last night. A powerful line of storms moved through the Midwest yesterday afternoon and evening, spawning numerous tornadoes, primarily in Illinois and Indiana. Here in Michigan we were spared the tornadoes but had to cope with a long night of high winds, gusting up to 70 mph along the Lake Michigan lakeshore.

tornadoes nov 17 2013

The high winds and heavy rains lead to widespread tree damage and power outages. Dealing with a yard full of damaged trees can be an overwhelming and sickening feeling for homeowners. If you are a homeowner or someone who advises homeowners, there are several good resources on the web to assist with the process of assessing storm damage to trees after a storm.


The National Arbor Day Foundation has a storm recovery website that provides practical tips for dealing with storm damaged trees. The website also includes resources for media including press releases and images that are useful for educating the public on steps to take during storm recovery.

The Minnesota Department of Natural Resources also has useful storm recovery information on their website.

For those dealing with storm damaged trees keep these points in mind:

-Stay at least 25 feet away from any downed power lines and contact local authorities to report downed lines.

-Damaged trees and hanging tree limbs are extremely dangerous. Trees that are damaged in storms often have decay or other hidden defect and can drop without warning. Walk around – not under – damaged trees and limbs. Keep children away from damaged trees.

-If you are unsure if you can safely remove a limb or damaged tree, always err on the side of caution and contact a professional arborist or tree service company.

-Be wary of ‘door-knockers’, individuals that descend on storm-ravaged areas that offer to perform tree clean-up or removal. Reputable, professional tree service companies rarely, if ever, solicit business door to door. Working around damaged trees is dangerous work that requires professional training and equipment. Look for arborists that are insured and certified by the International Society of Arboriculture.

Hello Charlotte!

I’m sure you haven’t been wondering where I’ve been for the past five months or so, but just in case you have, I’ve been reshuffling my life and relocating. Where am I now? The family and I have moved to Charlotte, North Carolina where I now work at Central Piedmont Community College. Why? Because we wanted to be closer to family, we wanted a warmer climate, and I wanted to spend more time teaching. That said, I had a great time at the University of Minnesota and have only good things to say about my time there.

The great thing about my new job is that I have the opportunity to teach a diverse student population a broad spectrum of classes. This coming semester I’ll be teaching five classes including Specialty Crops (we’ll be concentrating on hydroponic systems for growing veggies – it’s a great way to learn about what plants need to grow), Plant Propagation (My favorite! Everything from cuttings and seeds to budding and grafting), Greenhouse Management, Applied Plant Science and Plant Materials I. And Hey, if you live near Charlotte, I’d love to see you in one of my classes! CPCC is one of the most affordable schools in the country and the classes are open access – in other words anyone can sign up! Since I don’t have the chance to do as much research as I did in Minnesota, I’ve compensated by having my students conduct experiments in the classes – and we’ve had a lot of fun. We’ve done everything from extracting essential oils using cold fat and steam extractions to rooting cuttings using 2,4 D and spiking the atmosphere with carbon dioxide using soda bottles. I’ll be posting about all of these projects in the coming weeks. Meanwhile, it looks like vinegar based BBQ with fried okra for dinner!

My favorite on-line conifer resources

Posted by Bert Cregg

I just wrapped up putting together a species profile on grand fir (Abies grandis) for Great Lakes Christmas Tree Journal, which is the professional trade publication of the Michigan Christmas Tree Association. I do a lot of articles and presentations on conifers and while I draw on my personal experience and background as much as possible, invariably I’ll need to consult some references. Here are some resources that may come in handy if you need to develop a presentation or article or just want to know more about conifers.

Silvics of North America
Silvics is a forestry term that refers to the “study of the life history and characteristics of forest trees especially as they occur in stands and with particular reference to environmental influences.” Back in the day, just about every forester worth their salt had a weathered and dog-eared copy of Silvics of North America on the bookshelf. Today it is available on-line. Silvics contains lots of basic information about trees species; where they grow, how fast they grow, common best problems, and their genetics. Silvics also includes range maps from Dr. Elbert Little, which are a handy reference when you need to know whether or not a species in native in particular location.

gymno database
Gymnosperm database
Chris Earle’s website is a botanical tour de force. It covers all gymnosperms, not just conifers but, of course, conifers make up the biggest portion of the site. The Gymnosperm database includes species descriptions for essentially every conifer in the world. Many species descriptions also include images. Earle discusses taxonomy of conifers, which for many species, is taking more plot twists these days than an episode of ‘Law and Order’. There are often interesting tidbits under enthnobotany for many species. Bottom line, you can look up just about any conifer species you know on the database and learn something you didn’t know.

American Conifer Society Database
The previous two resources deal primarily with conifers in their native environment. The ACS is dedicated to the Horticultural aspects of conifers. The ACS database includes hundreds of species and thousands of cultivars. For Picea abies alone the database includes over 200 cultivars. For each cultivar the site presents information on hardiness zone, growth rate, form, color and other characteristics. Many descriptions also include photos.

How NOT to do an experiment

Over on Facebook I follow some groups who find provocative topics, and today’s “science fair” post was so over the top that I had to share it here.

science fair

Here’s the original post. Now the accompanying text about microwaves is whacky enough on its own (and well worth reading), but my primary interest is with the experiment. This exemplifies why there are basic rules for doing science.

This starts out okay – identical pots, the same type of media (I assume), similar sized plants – but then things go downhill:

1) Replicates are important. There is one treatment and one control, meaning that it’s impossible to run any kind of statistical analysis. Ideally between 10-20 replicates of the control and the experimental treatment are used in this kind of experiment. That’s 20-40 plants total.

2) Variable control is important. Plants in a windowsill are subject to light and temperature gradients. That makes analysis more complicated unless one has an extremely long windowsill so that all plants are treated uniformly. And then our researcher prunes the tops of the plants – yet another variable.

3) Consistency between treatments is important. It appears that the pot on the left is wetter than the one on the right – the media is darker. If it’s not draining well – for whatever reason – then you’ll have a hypoxic root environment. Plants don’t like that.

4) Objectivity is important. It’s difficult (impossible, really) for any researcher to be completely objective. Ideally, the pots would have been watered by another person and then labelled in such a way that the person recording the data would have no clue which was which.

I think it’s really important to get kids excited about science. But it’s just as important giving them guidelines about doing science in a way that advances their own understanding about how the world works. Otherwise, it’s just more fodder for the aluminum hat crowd.

For Mulch

Posted by Bert Cregg

Just a quick note up front that today’s post is a little data heavy, so if you’re still adjusting to this weekend’s time change; be advised.

A few weeks back Jim Urban wrote a post entitled ‘Against mulch’ on the Deep Root blog. The principle reasons he cited for his position were: 1) Mulch floats and can clog drains and releases “lots of phosphorus” as it breaks down, and 2) work by Gilman et al. that suggest that mulch does not reduce evapo-transpiration. We discussed the Gilman et al. paper ad nauseum here already so I’ll stick to the other points.

Most organic mulches float, it’s true. However, if mulch is repeatedly washing from a bed into a drain this suggests a problem with the design as much as anything. Second, I’m not sure what constitutes “lots of phosphorus”. Branch and stem tissue of hardwood trees is about 0.1% P. If we use just the bark as mulch, the P concentration is about 0.2 to 0.3%. Is that ‘lots of phosphorus”? I don’t know. I suppose if you put enough it down and allow it wash into a drain it could be.

So let’s stick to what we do know about landscape mulch. Linda has written the most comprehensive review of mulch out there and it demonstrates the benefits of mulch. Nevertheless I’d like to add some recent observations of my own to the discussion. These come from follow-up measurement on some studies that we have already published on shrubs and conifers. But I think our new data are important because they demonstrate the long-term benefits of much on tree and shrub growth.

2006 Conifer study. In 2006 we installed a trial to compare several different weed control strategies for newly planted conifers. Weed control, either by hand, Vis-pore mulch mats or 3” of coarse wood chips, dramatically increased tree survival.
swmrec mulch survival

After 8 growing seasons, trees that had the wood chip mulch or mulch mats had significantly greater caliper than trees that were not mulched.
swmrec mulch caliper

2004 shrub study. In another trial we compared the effect of various mulch types (wood chips, pine bark, hardwood bark) on growth of common landscape shrubs (golden globe arborvitae, Runyan yew, ‘Tardiva’ hydrangea, cranberrybush viburnum, and arrowwood viburnum). We re-measured heights of the shrubs study a couple of weeks ago (nine growing seasons after installation). To keep things simple here I’ve lumped the mulches together and simply compared mulched vs. un-mulched.

After nine years mulching increased height growth for all shrubs except the arborvitae.
mulch 2013 ht

Even more interesting is that the growth benefit of mulch extends beyond the establishment phase. If we start at age 4 and look at the relative growth rate for the past five years (i.e., growth increment for past 5 years / height at 4 years) we see that mulch continues to provide a growth advantage for all shrubs except the arbs.
mulch RGR

As I said at the outset, a little data heavy today but I think this is an import point. There is a lot of discussion these days about proper planting techniques but I think after-planting care often gets overlooked and mulching is an important part of that. That’s why I’m for much.