Knock It Off – Page 2 – The Garden Professors™

Buzz words are not evidence

I made this little image to try and make a point, not about Bt or GMOs or organic agriculture (all important topics for another day), but about the use of buzz words. I’m tired of the way words like “chemical” and “natural” get thrown around to try and make things sound bad or good. Neither of them are particularly useful terms because the definition of chemical is so broad as to cover just about anything, and “Natural” is more-or-less meaningless and entirely subjective.

So, my simple plea is to not let emotionally loaded buzz words sway you, but dig into the actual research and evidence to make decisions about what you think is good or bad.

Joseph Tychonievich

Rogues gallery

You know the word “rogue” as a noun and adjective, and probably from when Sarah Palin “went rogue” during her time as vice presidental candidate.

But you may not know that it also a verb. That’s the way I use it most often. I rogue plants and I complain — often — about seed producers not doing enough roguing.

To rogue means to weed out inferior or off-type plants. It is a critical part of producing and maintaining seed selections of plants. Whenever you are growing fields of plants for seed production, be it tomatoes or zinnias or corn, you get off types. Chance mutations, seedlings produced from errant grains of pollen from another variety, or just change of the diversity within the population. So one has to rogue — walk through the fields and pull out flowers that are the wrong color, corn plants that aren’t yielding enough, all the unexpected variants to keep the variety true to type.

The annoying thing is that a lot of seed producers cut corners — particularly, it seems, for annual flower seed — and don’t bother. The results can be very frustrating.

The worst are flowers in mixed colors. Maintaining a good mix of multiple colors requires careful roguing to ensure one color — due to greater vigor or just chance — doesn’t come to dominate. Lots of companies just don’t seem to bother.

Last year I bought a packet of Zinnia ‘State Fair’, an old, and wonderful seed strain, which was supposed to come in the full mix of zinnia flower colors.

I got pink. That’s all. Just pink. My whole row was pink. Not my favorite color of zinnia. Clearly the pink plants slowly came to dominate the fields of whoever is producing these seeds, and instead of roguing out some to bring the color mix back into balance, they just let them go rogue, and I got stuck with just one color.

The ‘State Fair’ zinnias were also supposed to be double, like this.

They weren’t. Single flowered forms will almost always come to dominate seed strains unless rogued out because they’re easier for insects to pollinate and thus tend to produce more seed. Clearly no one bothered, because every plant I sowed out gave me just a single row of showy petals.

I’ve had similar experiences with countless other varieties of seed annuals. The picture looks great on the packet, but sow them out and mostly what I get are rogues, not the variety I was after. The lack of roguing is a plague… bad enough that a friend in the horticulture industry once mentioned casually to me that, of course, cosmos varieties are only worth growing when they are first introduced. A few years without good roguing, and their desirable characteristics are mostly lost.

So more roguing please. I love growing big blowsy annual flowers from seed. I’m tired of them all going rogue.

Another unnecessary tree failure

The end of August brought an unseasonable rain- and windstorm to the Puget Sound region. We had some spectacular tree failures which I missed seeing as I was out of town. But one of our Facebook group members, Grace Hensley, was on the ball and took some great photos of a fallen purple-leafed plum. The first thing you see is the complete lack of a stabilizing root system.

"Rootless" purple leafed plum — “Rootless” purple leafed plum

Now look at the base of the trunk, which is actually a massive circling root that has girdled the trunk over time.

A big wooden donut — A big wooden doughnut

By now you must be able to see the orange twine extending from the base of the tree to the soil. Yes, those are the remains of the balled-and-burlapped clay root ball that was planted many years ago. Commercial landscapers will assure you that tree roots can grow through the burlap and establish. And this is sometimes true, as in this case.

But what doesn’t happen when the whole B&B mass is plopped into the ground is that circling woody roots aren’t discovered and corrected. Over the decades what started as a small circling root grew bigger and bigger, slowly squeezing the trunk and preventing it from developing girth at that point. It’s kind of like a blood pressure cuff being pressurized but never released.

Trunk growth was prevented by the girdling root. The broken part here used to be in middle of the wooden doughnut.

In time, the constricted point becomes so unstable that the tree breaks. Look are how small the trunk that’s still in the ground is compared to the trunk of the tree itself. Windstorms are often the final push these failing trees need.

How long before this neighboring tree fails, too?

Commercial landscapers say it’s too costly to remove the twine and burlap and clay surrounding the roots, not to mention doing any of the corrective root pruning that might be needed. It’s easier to just plant the whole thing and cross your fingers that the tree lives past the warranty date. This is what happens when you consider a tree as just another design element rather than a living organism.

As a homeowner, however, you can insist that your trees are planted correctly (if you have someone else do the work). Or you can do it yourself. The bare-root method (sometimes called root washing) is an emerging science and it requires thoughtfulness, but it’s certainly better than the conventional approach in terms of long term tree health.

A new excuse for bad pruning

I spent last week in Orlando at the ISA annual meeting (that’s the International Society for Arboriculture). It’s a great venue for networking with colleagues and hearing about the latest tree research. And once in a while I’ll have a WTF moment. (That stands for Why Trees Fail in case you’re wondering.)

My WTF experience this year revolved around some new terminology and techniques. I learned there are now “environmental arborists” who practice “retrenchment pruning.” In the last few days I’ve tried mightily to find some standard definitions from reputable sources. I don’t know what an environmental arborist is, since it’s not a certification (like an ISA certified arborist) nor is it a university degree program (like urban forestry or environmental horticulture). It seems to be a self-anointed title.

This is what a mature oak should look like. — This is what a mature urban oak should look like.

But the real WTF issue is retrenchment pruning. I looked in vain for published research through my usual data bases and found nothing – other than two articles in Arboricultural Journal (which is not the same as ISA’s journal – Arboriculture and Urban Forestry). Neither of the articles presented experimental evidence to justify this radical approach to pruning trees. Instead, they are more philosophical in nature, with a smattering of ecological theory.

Fortunately, retrenchment pruning methods are easily found on the internet, along with horrific pictures illustrating the results. As described on various websites, retrenchment pruning imitates the natural process of aging. Practitioners remove live branches or partial trunks to reduce the size of the tree and prevent future failure. These aren’t clean cuts, either: they’re “coronet cuts” or “natural fractures.” The rationale described in one of the Arboricultural Journal articles is that these jagged broken branches and trunks “promote specialist habitats and enhance colonisation rates of niche species.” In other words, this technique creates large wounds that are easily colonized by various insects and microbes.

An example of natural fracture pruning (http://www.countytreesurgeons.co.uk/veteran.html)

So apparently we’re expected to ignore the well-established field of woody plant physiology (which happens to be my specialty) and related practical bodies of knowledge (e.g., formal and informal pruning techniques of said woody plants) and start hacking away at mature trees. In doing so, we’re removing live tissue and creating large wounds. This has the effect of both reducing photosynthetic potential of the tree as well as opening it up to possible pest or disease invasion. But nowhere are these possibilities discussed as part of the “natural aging process.” Nor was there mention about how to manage the epicormics shoots that result from improper pruning. And they do need to be managed.

These are epicormic shoots resulting from topping this tree.

I saw some very angry arborists at the ISA meeting who were incensed at the idea that we should deliberately malprune trees. But others seemed quite excited with this new philosophy. To paraphrase one of my plant physiology colleagues, “Give a bad arboricultural practice a catchy name and it magically becomes legitimate.”

The cardboard controversy

I’m not a fan of using corrugated cardboard as a mulch, which like other sheet mulches creates problems for the underlying soil. Long-time readers of this blog may remember several previous posts (1, 2, 3 and 4) on this topic and I won’t belabor the points made in those posts. Instead, today I’m doing to focus on cardboard itself.

First, cardboard is a generic term that can refer to many types of manufactured paper. The box you see delivered to your front door is more properly called corrugated board or containerboard. It consists of two layers of linerboard sandwiching a layer of accordion-like fluting material. The linerboard is made from sheets of pulp that may be coated to improve smoothness (more about this later). The finished linerboard is laminated using adhesives to both sides of the fluting material.

Corrugated boxes are built to be tough. — Corrugated boxes are built tough

These boxes are made to withstand rough handling and to protect the contents from the external environment. It’s tough stuff: while you might be able to bend a piece of corrugated board fairly easily, it’s more difficult to tear it in half. The more heavy duty the box, the more difficult it is to bend or tear its walls.

So let’s now consider using this tough material in your garden as a mulch. It may be coated as mentioned earlier to improve smoothness. That’s going to prevent it from absorbing moisture. The coating also reduces the ability for gases to move between the soil and the atmosphere. In fact, smoothness is measured using an air leak method – the smoothest materials have the least air leakage.

Photo credit vizpix at Flickr — Photo credit: vizpix at Flickr

A garden or landscape mulched with cardboard (or heaven forbid several layers of cardboard as part of the science-free lasagna mulch method) is now covered with a tough, relatively gas- and water-impermeable material that will take some time to break down. It’s hardly a mulch that’s going to nurture soil life.

But cardboard mulch fans swear that they find more earthworms under cardboard than anywhere else in their garden. This is almost always the first response I get from gardeners who don’t believe that cardboard causes problems. And this is where it’s important to consider earthworm behavior.

Photo credit: Kurt B. on Flicker — Photo credit: Kurt B. on Flickr

We’ve all observed that earthworms crawl to the soil surface during heavy rains; this is due in part to water filling their burrows and reducing oxygen availability (Chuang and Chen demonstrated this nicely in 2008). Likewise, the reduction in oxygen movement from the atmosphere into cardboard-covered soil would cause worms to crawl upwards in an effort to find oxygen at the soil surface.

So don’t assume your lasagna mulching draws earthworms to your garden. It’s more likely that you’re smothering their habitat.

***An update on cardboard gas permeability. We’ve just published an article comparing diffusion rates of different mulches. You can find the article here but it is behind a paywall. Here is a graphic comparing diffusion rates of various mulches. This is a logarithmic scale.
Now, until cardboard proponents publish evidence to the contrary, it’s pretty obvious that cardboard mulch interferes with gas diffusion.

***And another update on how our blog works. This post, by far, is the most popular. It generates a lot of comments. All comments must be approved before they’re posted, and I don’t approve comments that are derogatory or promote a belief in the absense of supporting science. If you want your comment to be published, be polite and provide evidence to support your statements. Otherwise, you are wasting your time.

***Another update on cardboard in your garden: A recent paper reports on PFAs (aka “forever chemicals”) in various products used for poultry bedding (among other things). Cardboard was one of the worst. The article is behind a paywall but I have access to it and was able to find the table shown here. So if you need yet another argument to NOT use cardboard as a mulch (like in “lasagna gardening), maybe “keep forever chemicals out of your garden” will do it.

**Look at the top line for shredded cardboard and then the last column which has the PFAs data. Not to mention all the other contaminants listed.**

Out of the bottle and into the bag

Last week I was having lunch with my mom at our favorite nearby nursery/café. After failing to resist the grilled cheese sandwich (3 cheeses! And buttery panini bread!), we walked off lunch in the garden supply part of the nursery. Normally I’m on my best behavior when I’m shopping with my mom (i.e. I don’t take photos of things I’m going to take to task on the blog). But like the 3-cheese grilled sandwich I was unable to resist the bags of biodynamic compost.

Biodynamic compost is now available at garden centers

Long-time readers of the blog may remember my earlier column and post on biodynamics. Since I wrote the original column over 10 years ago I’ve watched biodynamic marketing move from boutique wines to coffee, tea, tomato sauce…and now to garden products. Really expensive garden products, as in $19.99 for one cubic foot of compost.

An "untapped source of power and majesty" makes this compost different. — An “untapped source of power and majesty” makes this compost different.

What makes this bag of compost worth $19.99? One has to assume it’s the biodynamic preparations used to treat the compost. They’re referred to in the label under “concentrations of yarrow” and so on. Do these preparations make a difference? The label suggests it might be to restore the soil’s vitality. Is there validity to this claim?

It's doubtful that all of these ingredients are locally available. And why are so many materials needed? — It’s doubtful that all of these ingredients are locally available. And why are so many materials needed?

In 2013 I published a review of the scientific literature on biodynamics, specifically looking at whether biodynamic preparations have a measurable impact on anything they’re applied to. In a nutshell, the answer is no. (Though this article is behind a paywall, I can send a pdf to you by email if you’d like to read it.)

Don’t let packaging and magical words sway you. Compost made with local materials like bark or agricultural wastes and certified by the US Composting Council is reasonably priced and sustainable.

Stuck in the middle with you

Clowns to the left of me,

Jokers to the right, here I am,

Stuck in the middle with you

More than once in the past couple months I’ve come close to pulling the plug on FaceBook. What started as a fun and easy way to keep up with family and friends back home and stalk old girlfriends has devolved into an infinite do-loop of whininess, acrimony and vitriol over GMO’s, organic food, vaccines, and President Obama. Of course, I brought a lot of this on myself based on the virtual company I choose to keep. While my allegiances generally align with groups such as GMOLOL, GMOskepti-forum, and the Genetic Literacy Project, more and more I find myself just as appalled by their tactics and rhetoric as I am by those of the anti-GMO side. I have many thoughtful and intelligent friends that think GMO’s should be labeled or even banned and I’m fairly certain none of them want poor African children to go blind.

Quick aside here: Raise your hand if you have ever changed your mind on an important issue based on an internet meme.

The problem in this type of discourse is that everything has become an all or nothing game. If you concede even the slightest point to the other side, you have become a wishy-washy capitulator. But the underlying problem is the answer in science is often “It depends.” In the GP blog and elsewhere, much has been made of the Pew Research poll that showed the biggest opinion gap between the scientists and the public was over GMO safety. Had I been polled, I would have agreed that GMO’s are generally safe. But that doesn’t mean I don’t think there are concerns. Heavy agricultural use of glyphosate is leading to the development of Round-up resistant weeds. Likewise, the potential of GMO crops out-crossing with native plants cannot be discounted. Scientists working on GMO’s, of course, are aware of these issues and are constantly working on steps to manage and minimize these risks, but they could still come back someday to bite us in the butt – the risks, not the scientists.

Another problem with controversies on the interwebs is that issues get over-simplified. The endless argument over organic food is just stupid. Saying organic production is better than conventional farming (or vice versa) is like saying Ford is better than Chevrolet: You can’t compare without knowing which model: Pick-ups? Sedans? SUV’s? Or what’s being compared: Gas mileage? Crash safety? Resale value? The same is true with organic vs conventional: What crop? Celery? Apples? Carrots? Lettuce? And what measure? Pesticide residue? Carbon footprint? Food safety? The debate is an interminable game of whack-a-mole. I suspect anyone with access to ‘Web of Science’ and an afternoon to kill could come up with a couple dozen studies to support either side. My personal view is I’ll pay a modest premium for organic produce if it clearly looks better, or in the case of small fruits that I can sample before I buy, tastes better than the conventional counterpart.

The other issue in the social media wars is that we need to admit and accept the limits of our knowledge. The Pew poll and other surveys indicate that most scientists agree that climate is changing due to human activity. Again, I’m with the majority of scientists on this. But only a small portion of those scientists are actually trained in climatology and understand and appreciate the nuances of the Global Circulation Model or the Pacific Decadal Oscillation. What I know with certainty is that CO2 and other greenhouses gasses have risen consistently and dramatically since the Industrial Revolution. How will that impact climate in 100 years? I have no clue beyond what the climate scientists tell me. Do I have any reason to doubt their projections of steady increased temperatures? None beyond the fact the GCM, like all models, is only as reliable as the data and assumptions it is built on. Does this make me a right-wing climate change denier? Hardly. But I am self-aware enough to know what I don’t know.

Bottom-line, even on issues where a vast majority of scientists agree, there are still unanswered questions and areas of uncertainty and always will be. In the meantime, we still have to make policy decision with the information at hand. Talking about these issues intelligently and respectfully will get us further than derision and mockery.

In the meantime, if you open up FaceBook and I’m not there, you’ll know I’ve finally had my fill.

Spec errors mount

For years I subscribed to Consumer Reports. I appreciated their objective approach to product testing and lack of advertising. In their own words, their policy is to “maintain our independence and impartiality… [so that] CU has no agenda other than the interests of consumers.” But recently they’ve veered off the science-based trail – at least the one running through our gardens. Their approach to plant and soil sciences is more pseudo than science. And last year, after 30+ years of loyal membership, I quit my subscription when Consumer Reports began partnering with Dr. Oz (see here for instance ).

So until today I’ve been blissfully unaware of whatever CR has published on gardening and garden products. Then this post appeared on our Garden Professors blog group page ). I’ve included some of the article below along with my italicized comments in brackets.

“Lawn care without the chemicals: rid your yard of weeds and pests with these mostly organic solutions”
“…Here are 10 common weeds and pests that plague homeowners nationwide, along with chemical-free measures [“chemical-free?” Well, we shall see.] that should be effective in bringing them under control. For more information, go to the websites of Beyond Pesticides and the Great Healthy Yard Project. [Neither of these two sites is remotely scientific or objective.]

“Dandelion – what is it? A perennial weed whose common yellow flowers turn to windblown seed. Telltale signs. Though a handful of dandelions is no big deal, a lawn that’s ablaze in yellow has underlying problems that need to be addressed. How to treat. Like many broadleaf weeds, dandelions prefer compacted soil, so going over the lawn with a core aerator (available for rent at home centers) might eradicate them. [Like many broadleaf weeds, dandelions will grow anywhere. That’s why they’re called weeds.] It also helps to correct soil imbalances, especially low calcium.” [I’m curious how CR determined a “soil imbalance.” And did they test their hypothesis experimentally?]

Dandelions obviously suffering in a calcium rich soil

“Barberry – what is it? An invasive shrub with green leaves and yellow flowers, often found in yards near wooded areas. Telltale signs. Left unchecked, the shrub’s dense thickets will start to choke off native trees and plants. How to treat. Cut back the stems and paint their tips with horticultural vinegar or clove oil (repeated -applications may be needed). Burning the tips with a weed torch might also work.” [Yes! Chemical free vinegar and clove oil! By the way, clove oil has NO demonstrated efficacy for this application. And I’m sorry, but “burning the tips” of barberry is just going to stimulate lots of new growth below the damage. Just out of curiosity, how many people have problems with barberry in their lawn?]

I think you’d notice this in your lawn…

“Crabgrass – what is it? An annual weed with a spreading growth habit. It’s common in the Northeast, in lawns with poor soil conditions. Telltale signs. Lots of bald spots, especially after the first freeze, when crabgrass dies off. How to treat. Have your soil tested. Lime or sulfur may be needed to adjust the pH. Aeration is also recommended. Corn-gluten meal, applied in early spring, can be an effective natural pre-emergent herbicide. [Corn gluten meal, applied in early spring in climates where it rains, is an effective fertilizer for crab grass.]

Crabgrass with increasing levels of corn gluten meal.
Courtesy of Tom Cook, Oregon State University.

“Kudzu – what is it? An aggressive climbing vine that’s common in parts of the Southeast and the Midwest. Telltale signs. The thick vine forms a canopy over trees and shrubs, killing them by blocking out sunlight. How to treat. Pull out the vine and, if possible, its taproot. Be sure to bag and destroy the plant or its vines will regerminate. If the root is too thick, paint the stump with horticultural vinegar or clove oil repeatedly, or burn it with a weed torch.” [Ditto the comments for barberry.]

Have fun painting stumps. (Wikimedia)

“Canadian Thistle – what is it? An aggressive creeping perennial weed that’s found throughout the U.S. Telltale signs. Look for outbreaks in vegetable gardens, particularly those with peas and beans. [I have no idea where this little nugget of nonsense came from. It’s a weed! It will grow ANYWHERE! It doesn’t need peas and beans!] How to treat. Repeated hand weeding and tilling of the soil will weaken its extensive root system. [Because tilling the soil is such a great way of suppressing weed seed germination. And it’s really good for your lawn, too.] Planting competitive crops, such as alfalfa and forage grasses, will keep it from returning.” [Yes, do replace your lawn with alfalfa and forage grasses.]

Your new, improved lawn (Wikimedia)

“Fig Buttercup – what is it? A perennial weed with yellow flowers and shiny, dark green leaves. It’s common in many parts of the East, Midwest, and Pacific Northwest. Telltale signs. The weed will start to crowd out other spring-flowering plants. It can also spread rapidly over a lawn, forming a solid blanket in place of your turfgrass. How to treat. Remove small infestations by hand, taking up the entire plant and tubers. For larger outbreaks, apply lemongrass oil or horticultural vinegar once per week when the weeds first emerge. It might take up to six weeks to eradicate.” [Now in addition to pouring vinegar on your lawn, we’ll try lemongrass oil instead of clove oil. Another unsubstantiated application – maybe lemongrass because buttercups are yellow? Makes about as much sense as anything else. It smells nice though.]

Color coordinated weed control

“Phragmites – what is it? An invasive grass species found nationwide, especially in coastal wetlands [where so many of us have lawns]. Telltale signs. Dense weeds can crowd out other plant species without providing value to wildlife. How to treat. Cut back the stalks and cover the area with clear plastic tarps, a process known as solarizing. Then replant the area with native grasses.” [Solarizing pretty much nukes everything that’s covered – not just the weeds. In fact, the rhizomes of this weed are so pernicious I’m not sure that solarization would work. Am still waiting for CR to test their hypothesis in an objective and scientific manner.]

Phragmites rhizome (Wikimedia)

So, Consumer Reports, I’d love to come back to you. But until you start applying your own standard of objective rigor to everything you cover, I’ll have to pass.

A scary Halloween story

Those of you that have followed the blog for a while know that poor tree planting is one of my pet peeves. It drives me crazy to watch tree installers use backhoes to gouge out gigantic holes and then drop in the intact root ball, clay, burlap, twine and all. But this dig-and-dump method (or “cost effective practice” according to installers) of installing trees often dooms them (the trees, not the installers) to a slow and ugly death. So in honor of Halloween, let me share my latest horror story.

Twice a day I drive down this street in NE Seattle. I’ve long admired the row of dead street trees left to remind us all of our own mortality. A few of these Liriodendron have somehow survived though “survival” seems a generous term. They’re more like zombies, slowly losing body parts but somehow still functioning until someone puts them out of their misery.

One lone tree seemed to defy all odds. Until our latest windstorm, which revealed the cause of all this arboricultural agony.

That’s right, there’s the clay-covered rootball, still intact. Only one root has managed to escape into the native soil. There may be others on the opposite side, but by now (several years after installation) there should have been sufficient root establishment to prevent failure.

Several of us have written about bare-rooting trees before, and while there’s still not consensus on the practice I think we would all agree that the tree planting in this case was not acceptable. There are better ways, and yes they take more time (or “not cost effective” according to installers), but planting trees right mean fewer replacements later.

What’s wrong with this picture?

The Seattle Times recently had a front page story on what Seattle’s new waterfront might look like. Back in 2009, the city began work on this project, hiring “rock-star landscape architect James Corner, designer of the celebrated High Line in New York City” to develop the big picture. (Note: I’ve been to the High Line and have posted on it before – it’s fantastic.) As you can see from the linked article from the Times, many of Corner’s architectural renditions for the greenway are presented, including this one:

COURTESY OF JAMES CORNER FIELD OPERATIONS AND CITY OF SEATTLE
An architectural rendering shows what a Pioneer Square beach at the foot of Washington Street could look like.

For those of you not familiar with Seattle’s waterfront, it’s built right next to Puget Sound, a huge inland sea connected at its mouth to the Pacific Ocean. So it was with much surprise that I saw what appear to be Douglas firs (Pseudotsuga menziesii) along the cobbled beach. Douglas firs are not particularly salt tolerant, nor would they be very happy with the tidal action or seasonal storms that will flood the beach on a regular basis. Even if these were not Douglas firs (native to Seattle) but some other salt-tolerant species (mangroves?), it’s doubtful they would look as picturesque as the drawing shows. Neither would the rest of the trees in the area, whose root zones would normally extend far into saline soils under the beach and sound.

Am I being picky? No, I don’t think so. Landscape architects should know better than to use plantings as decorations for their designs, like candy sprinkles on cupcakes. Plants aren’t just design elements. Choosing plants that are appropriate to a site is a science as well as an art.

I can’t believe that in the five years that Seattle’s been working on this project that horticultural science hasn’t been a major component of landscape planning.