Author: Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

Why I dislike rootgrafted plants

I’m pretty much a live-and-let-live person in terms of plant choices (as long as they’re not invasive).  But I’m becoming convinced that oddities grafted onto hardy rootstocks are poor choices, because the rootstock always seems to win.  I posted one of these several months ago (see October 28, 2009 ), but just today have just found the poster tree for my anti-rootgraft movement.

A little backstory.  I’m currently out at the Washington coast, trying to get some writing and seminars done without disruption.  Today I had to make a trip into Aberdeen, the horrors of which will have to wait for another post.  Before going back to my retreat, I tried to renew my enthusiasm for life by seeking out bad plants.  I was well rewarded.

I have to give my daughter Charlotte credit for spotting these lovelies.  There were two of these $50 Betula pendula ‘Youngii’ trees available.  I felt like I’d stumbled upon the next winner of “America’s Next Top Model.”  I took pictures from every angle, full shots and close-ups, for your viewing enjoyment.

Note that the “unusual deciduous tree with pendulous branches” is a grafted tree, evidenced by the differences in girth at the grafting point.  You’ll also note the appearance of vigorous watersprouts emerging from below the graft.  (The bamboo stake to the left lost it function years ago, but is still adds an unexpected pop to the overall composition.)

And here she is in her full beauty!  The “S” curve of the scion is bisected longitudinally by two watersprouts, forming a giant $!  I do have to agree with the tag at this point – it certainly is “an excellent accent or specimen plant” for the Island of Misfit Grafts.

Finally, please enjoy yet a final reason I don’t like grafts:

(Hint:  Note the glue glob.)

Better Red than Dead!!!

David, one of our newer readers, asked why his red-stemmed roses seem to be more cold hardy than the green-stemmed cultivars.  So today’s blog will be dedicated to a brief discussion of why it’s better to be red than dead.

The brilliant red, blue, and purple colors seen in flowers and fruits are due to anthocyanins (and the closely related betacyanins).  These water-soluble, non-photosynthetic pigments are also commonly found in stems, leaves and other vegetative tissues.  In 1999 I wrote a review article exploring the reasons that leaves and stems might turn red.  A few years later I wrote another review, more specifically looking at how anthocyanins might influence plant water relations.  (This last phrase is plant physiology-geek jargon, and I have to admit that the class I took on this topic during my PhD work was the hardest, and probably most hated, of all the classes I took.  And now it’s turned out to be one of the most valuable.  Go  figure.)

While you hard-core types can read the review articles that I’ve hot-linked above, what I’ll try to do is summarize my hypothesis for why leaves (and stems) turn red.  Some leaves are red when young, then turn green when older.  Green, deciduous leaves turn red before they fall off in the autumn.  And some plants are genetically programmed to have red leaves all their lives.

The environment can also influence leaf reddening.  Drought, nutrient deficiency or toxicity, salts, heavy metals in soils, cold temperatures, low soil oxygen, whew!  All of these environmental factors have been attributed to temporary reddening.  What do these factors have in common?

It turns out that all of these environmental stresses directly or indirectly affect the ability of plants to take up and/or retain water. Because anthocyanins are water-soluble, they effectively dilute the concentration of water in the plant.  Look at it this way: any limited area will only hold so many water molecules.  A test tube of pure water has the maximum number of water molecules possible.  A test tube of water plus sugar (or salt, or anthocyanins for that matter) will have fewer water molecules, because the other substances take up space, too.  So effectively, anthocyanins reduced the apparent concentration of water in plant tissues.

Why is this important?  Well, anthocyanins in leaves helps reduce water loss, because the concentration of water in the leaves is reduced and evaporation slows down.  They also could serve as antifreeze compounds, allowing red leaves (and stems, David!) to be more cold hardy.  And if anthocyanins aren’t amazing enough already, they also (1) bind and transport sugars during fall leaf color change, (2) protect tissues against high levels of solar radiation, and (3) are natural antioxidants.  (That’s why you’re supposed to eat red fruits!)

I could go on and on, but I hope this might help explain why David’s red stemmed roses might be more cold hardy than the green variety. (And my thanks to my daughter Charlotte for allowing me to use her photos here.)

If I’ve seemed distracted for the last few months, this is why

I just got this today – it releases in February!
Isn’t it a great cover?

And this one came out the week before Christmas – my holiday gift to myself!  (You try riding herd on 21 different authors and see if you like it!)

Getting these books done was a major milestone, and I hope that this year I might have time for some new projects.

Happy New Year!

Foliage fun flaunted!

Not much activity on the Friday quiz!  It was a tricky one.  Take a look at our photos in total:

As you can see, these aren’t plant “problems” in the strictest sense.  (The “landscape” in question is a retail nursery.)  They are cultivated anomalies – little mutations that have been discovered and propagated.  There are several points to this exercise:

1)  Be sure you know your plant material!  Many peope mistakenly assume that plants such as these are diseased, pest-ridden, or lacking some nutrient and need to be “fixed.”  Personally, I don’t care for yellow cultivars; like Lisa B and Deb, I think they look chlorotic.  Without identifying tags, though , it would be hard to know these are not deficient in nitrogen or some other macronutrient.  I guess I would wait until leaves emerge in the spring:  if they were yellow then and stayed yellow, I would presume the plant was a yellow cultivar.

2)  Many of these cultivars are not particularly vigorous.  A plant that’s missing much of its foliar chlorophyll does not photosynthesize efficiently and would probably not survive in nature.  In our managed landscapes, however, we can nurture these oddities so they aren’t out-competed by other plants.

3)  Cultivars such as these often revert to the wild form (remember Bert’s quiz last week?).  The natural form (green vs. yellow leaves, or normal vs. dwarf stature, for example) is nearly always more vigrous than the mutation, and given the opportunity plants will outgrow these limitations.  Thus, many cultivars require careful maintenance to remove “sports” before they overtake the plant.

Sunday rant – the evils of chemicals

It’s days like this that I am so grateful to have this blog at my disposal!

It’s 7 am on Sunday and I’m just finishing the paper, drinking Earl Grey tea, and listening to NPR.  Liane Hansen just finished an interview with Martha Stewart, who among other things was discussing healthy eating for the new year.  She’s a proponent of organic food (as are many of us), and mentioned two reasons she doesn’t like conventionally grown produce.  The first – residual pesticides – is a legitimate concern.  But then she stated her second concern that “chemical fertilizers in the soil are taken up and stored in the plant.”

No kidding.

Plants really don’t care (excuse my anthropomorphizing) where their mineral nutrients come from.  Nitrogen in ammonium sulfate is the same element as the nitrogen in cottonseed meal.  The plant uses it for amino acids, chlorophyll, alkaloids, and many, many other compounds.

Martha’s faulty thinking falls into the “organic is safer than chemical” mindset that way too many people hold (you can read a column I wrote about this in 2001 here).  “Chemical” is not intrinsically bad and “organic” is not automatically safe.  This is an emotion-based argument and inspires fear rather than thoughtful discussion.  When someone parrots this mantra, I can’t take them seriously.

I believe that organic methods in production agriculture, ornamental landscapes, and home gardens are superior to conventional practices and support a healthy soil-microbe-plant-animal system.  I also believe that many fertilizers are misused and/or overused – but this includes both conventional and organic varieties.

Gerald Holton, a science historian at Harvard, once stated that “persons living in this modern world who do not know the basic facts that determine their very existence, functioning, and surroundings, are living in a dream world.  Such persons are, in a very real sense, not sane.”

This is the quotation that came to mind this morning.

Friday Foliage Fun!

Take a look at these three closeups of foliage from three different plants in a landscape in Washington state:

 

You’ve been asked to diagnose what’s going on in this landscape that would cause these foliar abnormalities.  (I get photos emailed to me all the time asking these kinds of questions.)  Bugs?  Disease?  Nutrient deficiencies? Environmental conditions?  All of the above?

More photos and answers on Monday!

Invasives! Natives! No, wait, biodynamics

Just had to get your attention there.  We’ve had a great discussion over native and nonnative plants over the last few weeks.  I’m going to completely switch gears and move on to another topic  – biodynamics.

If you’re not familiar with this term, let me refer you to my online column here.  Biodynamics is a set of agricultural practices based on a belief system, not science, but is an increasingly popular approach, especially in the wine industry.  (You can read a discussion of biodynamics in the vineyard in The Skeptical Inquirer here.  This article is engaging as well as accurate – my column is pretty dry by comparison.)

Biodynamics is steeped in mysticism and includes special preparations that are used to treat soils and plants.  Preparation 500, for example, is created by mixing water with manure that has been packed into a cow’s horn and buried for a set amount of time.  Other preparations are more gruesome, requiring a stag’s bladder or cow’s intestine.  A whole certification process has emerged in support of these practices.

While it may be easy to dismiss these practices, it turns out that biodynamic farms or vineyards are generally healthier than conventional systems.  Does this prove a mystical force at work?  Not at all.  Biodynamic systems are also organic – using all of those good practices (low or no till, reduced pesticides, reduced fertilizers, polyculture, etc.) that have been demonstrated to be effective over decades of research.  When comparisons are made between biodynamic and conventional systems, the impact of organic practices are hidden.

The few scientific studies that have compared biodynamic to organic systems – in other words, specifically testing the effectiveness of special preparations – have found no repeatable, significant differences.

Why do I even care about this?  Well, it’s because it’s pseudoscience.  It’s a practice that takes on the mantle of science, but doesn’t stand up to repeated scienific testing.  Belief systems can’t be tested – even the inventor of biodynamics asserted that his methods were “true and correct unto themselves” and didn’t need to be tested.

Apparently simply being organic isn’t sexy enough anymore.

Is there any future for a scientifically-sound gardening magazine?

(You’ll see two posts from me today.  This first one is easier to do at 6 a.m.)

One of the efforts I’ve been involved with is serving as science editor (and writer) for MasterGardener Magazine.  We started this quarterly publication in 2007 (take a look at it online at it here) – not just for Master Gardeners, but for anyone interested in sustainable gardens and landscapes.  Sadly, the publication went to an annual issue last year because of the economic downturn and now may be eliminated altogether.

Yes, this is a Washington state publication so when native plants discussed they are local natives.  But the information itself is applicable no matter where you live.  We had hoped at one time to offer regional issues, so that the magazine would have a local flavor.

Anyway, the publishers are no longer willing to carry a loss on the magazine.  What they really need are advertisers.

Any suggestions out there?  Most useful will be ideas that I can do from my computer or phone.