What can CO2 do for you?!

Well, it looks like the climate change skeptics are starting to hedge their bets.  Global climate is not changing.  But if it does change, it’ll change for the better.  At least that’s the gist of a book by the Center for the Study of Carbon Dioxide and Global Change entitled “The Many Benefits of Atmospheric CO2 Enrichment”.  The book documents 55 different ways that increasing global CO2 will benefit the world.  Most of this is built on studies documenting increases in plant growth and/or photosynthesis associated with increasing CO2.  If you’re interested you can look at a preview of the book at:

http://www.co2science.org/education/book/2011/55BenefitsofCO2Pamphlet.pdf

While CO2 enrichment can benefit plants and trees in the short term, it’s less clear how they will respond over the long term.  For example, nutrition or water may soon become limiting such that the full CO2 ‘fertilization’ effect is never realized.  Also, it’s likely that certain plants will benefit more from increased CO2 than others: Will exotic invasives gain an additional advantage over natives?  And, of course, if rising CO2 results in increased global temps (which the Center denies) then all bets are off.

 

You can learn more about the Center for the Study of Carbon Dioxide and Global Change at their website http://www.co2science.org/  There is a tab on the homepage where you can donate to support their cause.  Why not?  Exxon/Mobil already has.

Wet trunk – the whole story

We had a flurry of discussion on this over the weekend. The diversity of possible answers shows you how difficult it is to do diagnosis with only some of the information available. That being said, several of you (Gail, Tom, Dave and Jimbo) all had portions of the problem identified. Here’s the whole picture:

As both trunks of this double-leadered tree have continued to expand in girth, they’ve created the perfect conditions for disease to occur in the narrow constriction between the trunks. Though I’m not a pathologist, I would agree with an initial diagnosis of slime flux.

In addition to the poor structure and disease issues, the location of this tree – next to a street, sidewalk, houses, and across the street from a school – simply shouts for removal before it inevitably fails and causes damage or injury.

Nice job – and thanks for doing your homework over the weekend!

Friday puzzle: wet trunk

Another diagnostic question today.  Below you can see the lower portion of a tree trunk whose left half is obviously wet:

What is directly causing the wetness (in other words, what environmental factor), and can you guess what led to this problem indirectly?

I’ll eliminate some of the obvious possibilities:  it’s not from dog pee, nor is it from a directional sprinkler.  And the answer to the second question is not in this close up photo, but will be revealed on Monday.

Why do I torment you like this?  Well, if nothing else, it gives you an idea of what distance diagnosis can be like – which is what we tend to do more and more, thanks to the internet and digital cameras.  Someone will send a photo of a plant problem and expect us to figure it out, but the answer may lie outside the field of view.

In any case, have fun!

Building a House of Straw — With Brix!

Before I get into the meat of this issue I wanted to mention that, a couple of weeks ago, Purdue came out with a statement which basically supported a post that I had previously written – one where I stated that there’s not a lot of good evidence that using Roundup leads to sudden death syndrome in soybeans. Yeah me! Well, not really – that’s not the way science works. While it is nice that other scientists agree with my conclusion, that doesn’t mean that Round-up isn’t affecting soybeans – it just means that there’s no evidence of it right now. Science doesn’t stop because a few scientists agree.

Same with compost tea – Linda and I have both posted about compost tea and we agree that, at this point, there’s no reason to use it. But science doesn’t stop, and it wouldn’t be completely surprising if, someday, someone comes up with a compost tea type product which is actually reliably useful.

Now on to the flavor of the day! Brix. So, what is brix you ask? Brix is a measurement of solids in a water (usually these solids are sugars). It’s easy to test brix by using something called a refractometer which measure how light bends when it passes through a thin film of water. We use brix in foods to tell how sweet they are. We just take a little sample of sap or juice, put it on a refractometer and bang, we know about how much sugar we have (actually, as I mentioned earlier, any dissolved solid, not just sugar, can alter measurements, as can non-solids, like alcohol. But the dominant thing affecting the brix measurement is usually sugar content).

Though it isn’t exactly mainstream, there is something out there called brix based gardening. Basically, the goal of brix based gardening is to increase the brix of the food we eat. Increasing the brix means increasing the sugar. The theory is that the higher the brix of a food the better it is – in terms of taste, resistance to insects, resistance to disease, healthiness.  The list goes on and on.

The biggest problem with arguing that gardening based on brix is a bad idea is that there is a nugget of truth in brix based gardening. Moreso than compost tea (in my opinion), brix has proven itself useful in certain situations.  Particularly in wine making, brix is used to quantify the sugar content of your grapes so that you can predict the sweetness of the wine you will produce (it will also help tell what level of alcohol you’ll get). As time goes on at the end of the season grapes increase their sugar content, so grapes are picked according to when the brix is right for the wine you want to produce.  Another grain of truth is that with higher brix you’ll get less insect pressure. This stands to reason, at least to some extent, because insects are usually looking for nitrogen rather than sugar.

But along with the little grain of truth comes some BS. For example, the idea that eating a food with a higher brix reading means that you’re eating a healthier food is just silly. It just means that you’re eating a sweeter food. The idea that higher sugar levels mean a healthier plant is also silly. In fact, one of the most significant things which can make brix go up is putting the plant under drought stress. Under drought stress, with less water, the concentration of sugars in sap naturally increases (because there’s less water to dilute it). Raisins are sweeter than grapes! Furthermore, the variety of the plant which you grow has an extreme effect on brix. Chardonnay grapes may have a low brix (around 21), a late harvest Riesling may have a brix of 42!

I have seen an inordinate amount of gobbledygook about mixing different fertilizers to get the perfect ratio of nutrients to increase brix. First, it’s important to realize that fertilizers can alter sugar content. For example, fertilizing heavily with nitrogen will increase growth of the plant but will usually decrease sugar concentration (hence brix). Indeed, from what I’ve seen, nitrogen seems to be the biggest player in sugar content.

That said, calcium and phosphorus based fertilizers seem to be the favorites among brix based gardeners – but from what I can find research hasn’t actually shown that these fertilizers increase brix on anything approaching a reliable basis. Another common recommendation is a molasses based fertilizer – once again, research on molasses doesn’t seem to show that it can do much to increase brix. Honestly, it looks to me like those recommending high brix as necessarily a good thing for us and our plants and then offering methods to do it are putting a scientific veneer on witchcraft – at least until further research comes along. I am sure that those favoring brix-based gardening will disagree with me – if you do and you read this I would welcome seeing some published papers which support your claims.

Parking tickets, compost tea, and pseudoscience in the Ivory Tower

Back in November 2009, Jeff posted an educational and amusing commentary about Harvard’s use of compost tea. Much vigorous discussion followed, and we’ll return to that topic in a moment. But first, I’d like to tell you about my morning yesterday.

In September of 2010, I received a ticket for parking longer than 2 hours in a restricted zone. Now, there was no way I committed this infraction; I had hard core proof that could not be rationally challenged. So, armed with my husband’s affidavit as to my whereabouts, as well as a dated receipt showing I was at the post office at the time when I was apparently parked several miles away, I went to court to challenge the ticket. During our briefing, the sitting magistrate told us we would need to provide a “preponderance of the evidence” to win our respective cases. For me, it was an anticlimactic turn of events, as the citing officer (whom I’d subpoenaed) did not show up, so the ticket was dismissed for lack of evidence.

And thus we return to today’s subject – use of compost tea without a “preponderance of the evidence.” Jeff took Harvard to task for buying into this “bullpucky”, I think he called it, and now Berkeley has decided to drink the Kool-Aid. One of my dear colleagues at University of Washington forwarded me a link announcing that Berkeley Botanic Gardens was adopting compost tea as an “eco-friendly fertilizing method.”

As the article reports, compost tea is being used

1) as a disease suppressant
2) to provide nutrients, and
3) to reduce the amount of water needed.

I’ve written a lot about compost tea, and I’ve reviewed journal papers on the topic as well. In a scientific nutshell, there is no solid evidence to support use of compost tea, particularly aerated compost tea, in disease suppression. Likewise, there is no evidence to support a nutritional role (I just finished reviewing a manuscript on this topic and the data were unconvincing). Finally, I cannot understand why spraying compost tea onto the leaves of a plant would reduce its water requirements. The “preponderance of evidence” is truly lacking.

Students at Berkeley have the dubious honor of supporting this nonsense through their student fees: $11,000 has been spent on a 300 gallon tank, worm composting bins, and a spray tank.

Whatever happened to using good old compost, and letting nature create its own “tea?” (Compost used as a mulch also helps reduce irrigation needs.)

Lasso those grasses!

While Jeff and Bert were swilling beers and eating burgers last weekend (dang, wish I was there to commiserate!) I was whacking back the last of the perennials and grasses in our home garden.  Tarp after tarp were filled with winter’s debris for compost pile as we fought 25 mph gusts the entire time.  Not ideal conditions.  However, a neat trick I learned years ago came in handy with the grasses.  I’m assuming many of you utilize this technique also – so forgive me if this is a “nothing new” post  Here’s Paul and Dabney, our Hahn Horticulture Garden horticulturists, demonstrating said technique:

Just cut below the web strap or rope with your favorite implement of destruction, and toss the whole bundle on the tarp to get it to the pile. Note that they both have on safety glasses, and Dabney has on gloves.  I can’t stress enough the importance of gloves (and long-sleeved shirts) when handling dried grasses. One of our student workers sliced his finger open to the tune of three stitches last week.  He was cutting down Arundo donax, Paul asked him to put some gloves on, but since 22 year-old guys are indestructible, he blew off the advice. Just saw him working out in the garden today with gloves on, yay!

Weigh in with YOUR garden clean-up tips – ’tis the season (for most of us north of USDA Zone 7 in the northern hemisphere).

Garden Professor Trivia #2: Who’s the tallest GP?

[This could get interesting…Oldest! Weirdest! Heaviest drinker! Most traffic tickets! Most cats! Most obsessed with slugs! etc.]

Keep Calm and Carry On…

This past weekend GP Jeff Gillman and I were in Midland, Michigan for two different conferences and had a chance to catch up over dinner (Boulevard burgers – best in Midland) and a couple of cold Bell’s stout ales.  It was nice to visit with Jeff since we have so much in common but rarely get to see each other.  As you might suspect, our conversation centered on negotiating the perils of the tenure and promotion process at research intensive universities, dealing with bumbling administrators, and, of course, our fellow Garden Professors.  Quick Garden Professor trivia:  Who’s the shortest Garden Professor? (Answer below).

Another item we discussed is how frantically worked up some people about following the various landscaping ‘rules’, especially for tree planting.

I have a program that I do on soil amendments.  I present 6 or 7 examples from about 30 studies that I’ve collected from the literature that show that amending backfill when planting trees provides little, if any, value.  Invariably, 2 or 3 audience members race up to podium after the Q & A, veins popping out of their foreheads.

“You have to add compost/peat/hydrogel/cow manure/take your pick when you plant!” they sputter.

I counter, “No you don’t.  I just showed you a half dozen examples where it didn’t matter; if I had time I could’ve shown you two dozen more.”

The conversation usually turns one of two directions from there.

“Well, I saw a gardening expert on TV and they said you always have to add compost/peat/hydrogel/cow manure/take your pick when you plant.”

The other variation is: “Well, I always add compost/peat/hydrogel/cow manure/take your pick  when I plant trees and shrubs and they do great.”

            “Did you try any without the compost/peat/hydrogel/cow manure/take your pick? ”

“No, why would I? They always do great when I add compost/peat/hydrogel/cow manure/take your pick !”

As part of the soil amendment talk I present some data from a tree planting study which also included a comparison of width of the planting hole (1.2 times the width of root-ball, 2x root-ball width, and 3x root-ball width).  After three years, width of planting hole had no effect on shoot or diameter growth.  At this point in the talk I wait ten seconds before I move on to allow the results to sink in.  By the time the next slide hits the screen half the audience is in a state psychologists refer to as ‘cognitive dissonance’.

People just can’t get over it.  Another race to the podium after the talk, “But you have to dig the hole 3 times the width of the ball.”

            “Can if you want to, but I wouldn’t say have to.”

“But, but…”

Clearly, there are things that shouldn’t be done when planting trees, like planting too deep.  But a lot of things we “know” are based on what sounds right, on what feels right; not necessarily on science.  Many practices have worked their way into extension bulletins, fact sheets, and our communal knowledge through sheer repetition.  Often times, these are things that won’t hurt the tree (adding amendments or making a wider planting hole) but make the job harder than it has to be.

Point is, we need to take a deep breath, get a grip, and be careful with absolutes like ‘never’ and ‘always’.  Working with trees is a lot like working for a university; it requires a high tolerance for ambiguity.  Trees are living dynamic organisms that are able to respond and acclimate to their environment.  I’ve stated many times that trees often grow more in spite of us than because of us.  So calm down and carry on.

GP Trivia answer: At a hair over 5’8”, I am the shortest GP.

The roots of the rhody problem

There were several good shots at analyzing Friday’s unhappy rhododendron.  Mature leaf size can be determined by light levels, as both Lisa B and Tom &  Paul suggested.  Moving a plant from a low to high light environment could cause this change in leaf size.  This rhododendron hasn’t been recently transplanted, however, so we can eliminate light levels as a cause.  (And there was no other impediment to light, such as the presence of shading plants.)

Lack of nitrogen was mentioned as well; but a lack of nitrogen would have resulted in chlorosis in newer leaves as well as smaller leaf size.  In this case, the new leaves are not chlorotic.  (The chlorosis on the older leaves is probably a phosphate-induced iron or manganese deficiency.)

Foy alluded to issues with water…and indeed that’s what I believe is happening with this rhododendron.  Plants that exhibit smaller mature leaves in subsequent years are often limited by water.  Full turgor is needed to force leaves to expand fully; without this physical pressure from inside, leaves fail to expand and once cell walls have lignified, leaf expanion ceases. 

Lack of sufficient water during leaf expansion could be related to irrigation, though in our wet spring climate this is rarely a factor.  More likely is a problem with the roots themselves.  Definitive diagnosis would require digging up the plant to find out whether its roots are still encased in clay and burlap (my guess) or if something else is restricting their ability to grow beyond the planting hole. 

Friday puzzle: unhappy rhododendron

Today we have a diagnosis question. Consider this unhappy rhododendron:

While there is more than one problem with this poor thing, the one I’d like you to think about is why the newer leaves are smaller than the old leaves. (They are fully mature.) There are two parts to this question:

1) What is the physiological reason that the leaves are smaller? (In other words, what is directly causing this difference?)
2) Knowing this, what does this tell you about the underlying problem? (This is related to diagnosing what’s happening in the landscape that you could actually see if you knew where to look.)

I hope that’s not too confusing! I’ll monitor the blog over the weekend and add clarification if I need to.

Answer on Monday!

Random thoughts from the NW Flower and Garden Show

Last week was Seattle’s NW Flower and Garden Show. This multi-day extravaganza features display gardens, educational seminars, and many opportunities to spend $$$. I had a little free time one day and shot some pictures, which I present here along with my commentary:

The Good

The “perfect” lawn is no longer just a monoculture of grass.  At least two of the display gardens had flowers scattered for a designer version of ecoturf:

And a very cool repurposing of old heating vent covers as part of a patchwork of groundcovers:

The Questionable

A gorgeous Japanese maple (Acer palmatum), “born” in 1893:

I’m sorry. I have a real problem with digging up 108 year old trees for a garden display. I would be surprised if this tree will survive its relocation, wherever that might be.  (Perhaps there was an explanation for this that I didn’t see, but mature trees should be moved only if absolutely necessary.)

I also wonder about the ethics of digging up a 700 year old alpine spruce (Tsuga mertensiana). I’m a fan of salvaging plants on sites slated for development, but somehow I doubt the Canadian Cascades are being threatened with condos.

And things that make you go hmmmm…


Pot…socks?  Diapers?


Blackberry vines as tree decor