Bert Cregg

Up, up, and away…

First, let me cue the 5^th Dimension.

I got a call the other day from the owner of a local hot air balloon company. They specialize in fall color rides and he wanted to include some info from me about the state of fall color in Michigan this year. Despite our concerns following this summer’s heat and drought, it turns out this year has been very good for fall color. I think our color has been a bit more variable than usual with some trees turning early and I’m noticing many maples are dropping pretty leaves quickly once they hit peak. Nevertheless, nature is giving us a great show. And if you’ve got a little extra spending money, there’s probably no better way to see it than from a beautiful balloon…

Photos: Scott Lorenz, Westwind Balloon Co.

</d

When all else fails…

As someone who has had a foot in Horticulture and a foot in Forestry throughout most of my career, people often ask me to compare the two disciplines. One of the truisms that applies in both cases is, “When all else fails, blame the nursery.” I’ve seen this following seedling die-offs in industrial forest plantations and I’ve seen it many, many times after street tree or landscape planting failures. In fact, if you believe some people, tree nurseries are responsible for every plague and pestilence to ever afflict mankind. Are some tree failures related to things that happened in the nursery? Of course. But there are lots of things that can go wrong between a nursery and a tree’s final destination; and even more things that can go wrong after it’s planted.

I know a lot of people don’t believe this, but nursery growers want their trees to survive and grow well after they leave their care. Growing trees is like making cars and any other business. You need satisfied customers if you expect to have repeat business. The best growers are always looking at their production practices for ways to improve their product. Last week I visited Korson’s tree farm in central Michigan. Korson’s grows Christmas trees and B & B landscape conifers. Rex Korson, the owner, has been concerned over the impact of root loss during transplanting of landscape trees. So much so, in fact, that he is conducting his own trial on root pruning.

For those that are not familiar, root pruning of B & B trees is usually done a couple years before harvest by using a tree spade to severe tree roots. The spade used for pruning is slightly smaller than the one used for harvest, so that new roots stimulated by pruning are harvested with the root ball. Does it work? I did a root pruning trial a few years back to see if it could improve survival of fall-planted oaks and had mixed results. For Rex’s trees, however, the initial results were pretty impressive. In the first photo below are root systems of Norway spruce trees dug with a 30” tree spade. The second photo shows the root systems of trees dug with the 30” spade that had been root-pruned last October with a 24” tree spade. The response in one-year’s time was dramatic. At this point there no out-planting data but, other factors being equal, increasing the amount of roots harvested with the tree should increase transplant success.

I should hasten to point out that Rex is not alone. I work with many other growers in the state that are constantly tinkering with this or that in their production systems; sometimes on their own, sometimes with university specialists or extension educators. I’m not so Pollyanna to think that everything is always rosy in the nursery world but most growers, especially the better ones, are aware of the issues out there and are working to build a better tree.

Spruce dug with 30″ spade without root pruning

Norway spruce root-pruned in Oct 2011 with a 24″ spade and dug Oct 2012 with a 30″ spade.

Close up of new fine roots

Tree spade mounted on excavator for root pruning. With this system an operator can root prune 8 trees in 5 minutes.

</d

Gone but not forgotten…

Got to spend Friday in the field in northern Michigan visiting growers and seeing some neat stuff: Great fall color, some natural concolor x Fraser fir hybrids and some awesome root systems produced by root pruning. Unfortunately, like the dog that ate the homework, my camera decided not to part with the images. I am tracking down replacements and will post an update on Friday.</d

The wackiness continues

It seems like every year we end up talking about ‘weird’ weather; either it’s extreme heat, extreme cold, too much rain, not enough rain, and on and on. Here in the upper Midwest and other parts of the central US, however, 2012 is clearly a year to remember. Our winter was fairly unremarkable until we hit 8 days over 75 deg. in mid-March. This pushed our growing degree days up at least 3 weeks and set the stage for widespread late-freeze damage in April, wiping out the state’s cherry, peach, and plum crops. Summer turned out warm and dry, highlighted by record-setting heat in July.

Weekly average high temperatures from MSU Hort Farm weather station: 2012 versus average of 15 previous years.

Now that we’ve seen some relief from summer’s drought and heat, we’re experiencing one more weather-related phenomenon: stress flowering. At my place I had lilacs and azaleas start to flower in August. We have also had reports of crabapples flowering in the eastern part of the state. Trolling around the web, I ran across a photo of magnolias blooming this month in Kansas City.

Magnolia flowering in mid-September. Source: Kansas City Star

So, what’s going on? Severe heat and drought can cause plants to go into a state of eco-dormancy. Typically we define “true” dormancy as a state where plants won’t grow, even when environmental conditions are favorable. Eco-dormancy represent the flip-side; plants should be growing but can’t due to severe environmental stress. In some cases the stress can induce flowering, such as we’ve seen this year. We have also seen examples of trees that have re-flushed, sending our new leaves after shedding leaves during the peak of the drought.

Will any of this cause long-term problems for trees and shrubs? Probably not. Stress flowing tends to be sporadic so most flower buds on a tree or shrub are likely to be unaffected. Shoots that re-flush late in the summer may or may not be able to harden off before winter. If not, they will be subject to freeze injury just like shoots that flushed earlier the spring. The main concern for 2012 is the cumulative toll of our environmental extremes.

The new hardiness map’s obsolete! The new hardiness map’s obsolete!

I posted back in January about my excitement about the update of the USDA Hardiness zone map. While I acknowledged some of the shortcomings of the new map, I was excited because it was a big improvement over the old map, both in terms of content (more recent temperature data included) and presentation (interactive search features, better graphics).

Dr. Nir Krakauer, assistant professor of civil engineering in The City College of New York’s Grove School of Engineering, was less impressed, however, and has essentially declared the new hardiness map dead on arrival. Dr. Krakauer conducted his own analysis of climatic data and determined that much of the country is already a half zone to one full zone warmer than the new USDA map. Why the difference? The USDA zone estimates were based on a simple average of annual minimum temperatures from the past thirty years. Dr. Krakuar’s applied a regression analysis to account for more recent warming. One of the key observations of the new analysis is that winter minimum temperatures are warming much faster than average temperatures, leading to the new hardiness zone projections.

So, what do we do with this information? All of the limitations that we associate with hardiness ratings still apply. Most landscapes experience micro-climates that may be slightly colder or warmer than the surrounding area. Plus, winter hardiness is just one piece of information in plant selection (we also need to also consider sun exposure, pest pressure, soil factors – drainage, soil pH, and so on). Most importantly, average temperatures don’t kill plants, extreme temperatures do. So whether we look at long-term averages or try to account for the most recent trends; the extreme 1 year in 5 or 1 year in 10 is what will cause issues. For example, if Krakuar’s projection is right and we’re a zone warmer on average, then the greater Lansing area is now zone 6b (0 to -5 deg. F). We’ve been colder than that in 2 out of the last 4 years.

The press release that accompanies Dr. Krakuar’s study starts with an attention-getting line: “Gardeners and landscapers may want to rethink their fall tree plantings.” But really things haven’t changed that much from the past. How homeowners and landscapers use zone information is still a matter of risk tolerance. If I chose a zone 5 plant and we’ve really warmed to zone 6, I’ve lost nothing. If I gamble and plant zone 6 plants and we drop back down to -10 or -15 deg. I may be looking for replacements. And, of course, there’s the tendency of many gardeners to ‘push their zone’, so we may have folks trying to grow zone 7 plants in Lansing. Which is fine – as long as people understand the risk. Actually I think a better approach to hardiness zones may be a probability rating: Are you willing to take a 1 in 10 chance your plant won’t make it? 1 in 4? 50-50? As new climate data are added to the model, garden centers could post and update the odds, sort of like the latest line at a sports book in Vegas. Those that want the ‘tried and true’ can stick with the old zone 5’s; those that want to live on the edge can pay their money and take their chances.

The good, the bad, and the ugly. A reply.

Ginny Stibolt of the Florida Native Plant Society recently posted Native Plant Issues: The good, the bad and the ugly, featuring me as the ugly. I posted a reply on her post, which I include here. To keep things in context, I encourage you to read her post first.

Enjoy your weekend!

Hi Ginny:

Some comments and a few points of clarification.

On the first item, as a Federal agency the USDA is bound by the Executive Order on Invasive Species which defines natives as species that occur in an ecosystem “other than as a result of an introduction”. I suspect they tried to simplify the language for the National Planting day release when they substituted ‘naturally occurring’.

On the Arbor Day Foundation, I am fairly certain they use contract nurseries in various locations for their tree sales. In any event, they have plenty of trained foresters on their staff that understand the importance of provenance and they would not send trees from northern seed sources to Florida or vice versa. But I certainly can’t fault the idea of supporting the Arbor Foundation, declining their trees, and buying trees from a local nursery.

On the Google + Hangout discussion no one was ‘booted off’. These were straight and simple technical issues. If people watch the Youtube video, the audio sounds like Neil Armstrong on the moon. This is a new technology for most of us and we are dealing with some growing pains. I would have much preferred even numbers on each side. Having an imbalanced debate can work against the majority, too. As Wilt Chamberlain famously observed, “Nobody roots for Goliath.” That said, we did have a lively and cordial debate and I hope people will bear with the grainy images and tinny audio and take a look.

Kentucky coffeetree

I haven’t watched the video but I don’t think I said there were no natives that could be used as street trees here in Michigan. If I did, I misspoke. That might be true for Linda in the Northwest – if you look at the native tree list for King county you’d be hard pressed to find anything that could be recommended in good conscience as a street tree. We have a few more options here in Michigan. If we were looking for a street tree for Lansing or Detroit the list could include hackberry, honeylocust, Kentucky coffeetree, tulip poplar, swamp white oak, and red maple. But even this list makes urban foresters cringe because they think red maples are already over-planted, tulip poplar is weak-wooded, and hackberry is difficult to transplant. With regards to Mary Wilson’s comments, there is a distinction between street trees and landscape trees. Landscape trees could be anywhere on a residential or commercial landscape where they could receive irrigation or other care so there is broader list, in contrast to street trees found on street sides in tree lawns or tree pits. Street trees are subject to the ‘worst of the worst’ in terms of environmental conditions; minimal rooting volume, compacted soils, road salt, and reflected heat load; but they provided the ‘biggest bang’ in ecosystem services, especially cooling buildings and sidewalks.

Swamp white oak

This has been an interesting discussion and clearly I have touched a nerve. I have to confess I have never been vilified so much in my life, which has been a little discomforting but also strangely flattering. When I met with Jeff and Linda earlier this week Jeff commented, “Wow, I’ve never been able to sit across the table from the devil incarnate before!” Fortunately, I work in academia where we spend most of our days telling one another how stupid the other is. People that seek to avoid criticism generally don’t do well in this line of work. Peer review forces us to critically examine our statements and sharpen our arguments. I was pleased and gratified to see some of the changes proposed for FNPS website and literature – why leave ‘low hanging fruit’ around for critics? While I didn’t appreciate some the comments made about me, if I’ve caused this group and others to strengthen their arguments and re-examine some of their assertions regarding natives, then the slings and arrows I’ve taken these past couple weeks haven’t been in vain.

Fearless fall color predictions

Happy Labor Day! Hopefully everyone had an enjoyable 3-day weekend. Labor day is the unofficial end of summer, which means fall is just around the corner. In fact, fall may be a little early this year around these parts. We are already starting to pick up some fall color – mainly maples, sassafras, and sumac. I usually get some calls from various media outlets asking for predictions on fall color. It’s always a dicey proposition. Weather going into fall is certainly a factor for fall color, but conditions during the fall itself are the final trump card. As I noted, we’re likely to see an early fall here in the Upper Midwest and, if we don’t start getting some decent rain, I suspect it could be a relatively short season as trees begin to drop leaves early due to continuing drought stress. Of course, all this can change relatively quickly if we get into a different weather pattern.

July 28, 2012. Sumac in fall color near DeWitt, MI.

Speaking of fall leaf color, the Fall Color Guy (aka Dr. Howard Neufeld, Appalachian State Department of Biology) has started his annual reports. http://biology.appstate.edu/fall-colors . This site is a great resource if you’re planning on doing some leaf peeping in the Appalachians. And even if you aren’t, I still recommend this site as one of the best on the biology of leaf color.

So, what’s your point?

My recent post on Seattle Public Utilities proposed restriction on the use of non-native plants for landscaping drew the ire of Taryn Evans of the Florida Native Plant Society. Taryn was critical not only of what I had to say but how I said it. She felt that my post was ‘clumsy’ and lacked a clear focus. In my defense, part of the perceived lack of clarity may stem from a lack of context. I alluded to several previous blog posts (including the references to using goats and schoolchildren to control invasives) but didn’t include the links – which are now listed at the end this post.

In terms of my other points, let me state my views as succinctly as possible.

I support promoting the increased use of natives in landscapes as part of an overall effort to increase landscape diversity and stability. Part of this is based on the notion that a diverse landscape –including natives – is buffered against various environmental and biological perturbations. But I also support natives because they provide a linkage to our native environment or sense of place. This second argument, by the way, is adopted by the California Native Plant Society http://www.cnps.org/cnps/about/ but is dismissed by Tallamy who states that his argument for native plants “moves beyond debatable values and ethics and into the world of scientific fact.”

I do not support legal restrictions that mandate the use of native plants in landscapes

Here are my concerns:

– The “scientific facts” regarding natives are not universally accepted by ecologists and are subject to debate as well. http://www.nature.com/nature/journal/v474/n7350/full/474153a.html#/ref8 A species’ need for water/nutrients/pesticides is a function of the environment in which the species evolved and not necessarily a native/non-native question. Invasiveness is an undoubtedly an issue, but exotic does not mean invasive. Some will argue that we can hedge our bets and prevent future invasions by planting only natives. And that is a justifiable position – I don’t agree with it – but I accept it as a rational argument. The dilemma with banning all exotics is that we throw the baby out with the bathwater and risk eliminating many useful plants.

– Natives can make great landscape plants in the right place but in many cases they are poor choices, especially in the built environment. Consider some of Tallamy’s recommendations from “Bringing Nature Home”:

Cottonwood. Cottonwoods are banned by many tree ordinances for their mess (cottony seeds and sticky buds) and are weak-wooded.

Maples. Maples are great landscape trees but we need to consider the fact that they are already overplanted in many communities. If we look at street trees and other public trees, maples make 50% or more of the tree population in some cities and towns. Does planting more make sense in these situations?

Ashes. Maybe if you live west of the Rockies, otherwise they’re a non-starter.

Lindens. Lindens have great form, growth rate and color. Unfortunately they are candy to Japanese beetles.

Elms. A handful of Dutch elm disease tolerant cultivars of American elm are available but the vast majority of trees available are Eurasian hybrids.

– Plants, especially trees and shrubs, evolve slowly. If we accept current climate predictions, trees planted today may experience very different climates in their lifetimes than those under which they evolved. The widespread outbreak of pine beetle (a native pest) in the Mountain West that is destroying millions of acres of pines could be an early indicator that changes in climate are already increasing stress levels and reducing the fitness of native trees.

Taryn was also critical of the tone of my post. For me and my co-bloggers this space is the editorial page of our lives. The blog is an opportunity to let our hair down a bit, vent on pet peeves, and sometimes shoot from the hip and play agent provocateur. No one likes to be criticized but it comes with holding our ideas up to public scrutiny and I accept that. I should note, however, that as the native debate moves from advocacy and education to codes and regulation, native advocates need to brace for increased criticisms and have their logical and scientific ducks in a row – which is the take-home theme of my post. Let’s face it, my critique was mild. As seen in the repsones to my post, some are quick to politicize or label the native case as disingenuous. Others would go further still and have labeled nativists as reactionaries and xenophobes (See http://arnoldia.arboretum.harvard.edu/pdf/articles/646.pdf or wade through David Theodoropoulos’s “Invasion Biology: Critique of a Pseudoscience). Obviously this is taking the argument to a ridiculous extent. I’m all for a fair debate where we can question statements and ideas but not motivations.

Earlier posts:

Are natives the answer?

Controlling invasives with schoolchildren

Controlling invasives with goats

Are natives the answer? Revisited

I started to leave a comment on Linda’s Friday post regarding Seattle Public Utilities proposed building codes regarding “Healthy Landscapes” but decided I’d weigh in with a regular post. Linda honed in on the 75% native requirement but there are lots of things to make one scratch their heads in the proposed codes.

Existing invasive plant species shall be removed and no invasive species planted.
No mention of how invasive plants shall be removed. Heavy-duty herbicides? Armies of school children forced into slave labor? Slow-moving ground-fire? Goats?

75% of all new plantings will be native to Western Washington.
So where did 75% come from? Sounds like a number that was pulled out of the air. How is 75% defined? 75% of plants? 75% of the area? And how does this foster “Healthy Landscapes”? If I have a 2 acre landscape and plant an acre and half of salal or Oregon grape I’ve met the requirement of 75% but have I increased species diversity or structural diversity or contributed to a “Healthy Landscape”?

A vegetation plan must be submitted for review.
By whom? What happens if they (whoever ‘they’ are) don’t like it?

Existing native plant species shall be protected whenever possible.
Sounds reasonable but what about existing non-invasive non-natives? Could a homeowner be required to cut down a 40-year-old red maple?

And on and on we could go. Let me state clearly, I’m not against native plants. Quite the opposite – I grew up in western Washington and have a passion for PNW plants since my high school days. Since moving to Michigan I’ve written articles and given talks promoting natives here as well. http://www.hrt.msu.edu/assets/PagePDFs/bert-cregg/GoingNative.pdf

Nonetheless, I think many in the native plant movement hurt their cause by parroting the same old lines without ever critically thinking about what they’re saying. Repeating a lie often enough times does not make it the truth.

Let’s critically look at some of the reasons for planting natives according to the Washington State Native Plant Society:

Native plants are adapted to our climate of wet winters and dry summers.
True. But so are lots of non-natives. Adaptedness is a function of the environment in which plants have evolved; whether it’s native or exotic. There are many climates around the world that are similar to the PNW and can produce similarly adapted plants.

Require less water than most non-natives once they are established.
Once again, adaptations such as drought tolerance are a function of the climate under which plants evolved. There are many exotic species that are more drought hardy than western Washington natives and likely to use less water.

Resist native pests and diseases better.
Sometimes. But unfortunately the days of worrying only about native pests are in the distant past. Exotic pests are here and they are here to stay. Dutch elm disease, white pine blister rust, emerald ash borer, chestnut blight, Japanese beetle, the list of exotic pests is long and getting longer. Native does not mean pest-free.

Improve water quality by needing less fertilizer and no pesticides.
OK, here’s where I get confused. The reasoning in Doug Tallamy’s book, Bringing Nature Home, is that native insects don’t feed on exotic plants, therefore if we plant exotics, native food pyramids will collapse and it will be the end of life as we know it. So… if native insects won’t feed on exotic plants, why would exotics require more pesticide use?

Save resources and encourage a sense of Stewardship.
Ok, now maybe we’re getting somewhere. Not sure why stewardship is capitalized here but if they mean a ‘sense of place’ or a ‘connection to the natural environment’ then I can buy it. Many native activists, including Tallamy, run away from this argument – apparently it doesn’t sound scientific enough – but it’s one of the best we have. Washington state has some of the most incredible plants anywhere. They should be celebrated and promoted and planted. In my mind, the biggest reason for planting natives – along with carefully selected non-natives – is to increase overall biodiversity. When I mention biodiversity I am speaking broadly; species diversity, structural diversity, age-class diversity, and landscape diversity. When we look to the future we have no idea what lies ahead. We don’t know what new, exotic diseases or insects are looming on the horizon. Most of us expect climate will change but no one can say with certainty how. Plants cannot evolve as fast as climate will change or as fast as new pest will be introduced. The only way to deal with this uncertainly is to spread the risk through diversity – this includes natives, exotics, and even interspecific hybrids.

It’s Meeting Season

Just flew in from Miami and boy are my arms tired – rim shot. Seriously, I just returned for the annual meeting of the American Society for Horticultural Science (ASHS) in Miami. Always good to wander the halls and renew old acquaintances and take in the latest in Hort science. Judging by the posters and talks here are some of the hot topics at this year’s ASHS meeting.

LED’s
Horticultural applications of Light Emitting Diodes (LED) are receiving a lot of attention these days. There are a couple of reasons for this. One, costs of LEDs are decreasing as manufacturing becomes more efficient. Two, LED’s can be built to generate specific wavelengths of lights. As many folks learned in biology, plants only use specific wavelengths during photosynthesis. Therefore LED’s can be used to only produce the light energy that plants need for photosynthesis – this can greatly increase energy efficiency. Aslo, incandescent light bulbs are being phased out of production. Old fashioned bulbs are not very efficient (they yield about 10% of energy used as light) but the light they do produce is effective for things like phot- period lighting (i.e., daylight extension for greenhouse crops). Since LED’s can be designed to reproduce the same wavelengths using much less energy, they may ultimately be a good substitute for incandescent bulbs.

High tunnels

Lots of interest these days in ‘high tunnels’ for fruit and vegetable production. These are not full-blown greenhouses but simply tall hoop-house structures big enough to grow fruit trees inside. One of the main benefits is season extension; allowing fruit or vegetable harvests earlier or later in the season than would be possible otherwise. This is especially important when we consider the local food movement for colder climates. There are also other, less obvious, benefits such as eliminating cracking of cherries due to rainfall.

Sensor-based irrigation systems

A hot topic, especially for the nursery crowd. There have been rapid advances in the reliability of capacitance probes and while costs are decreasing. In addition, there have been advances in wireless control systems. There are still challenges for nursery growers that have to deal with a diverse array of crop types and container sizes but researchers are definitely on the path of developing sensor-based systems that will automatically turn irrigation on and off in response to real-time soil moisture measurements. This will help to optimize plant growth while minimizing potential leaching of nutrients and chemicals.