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

Lunar control? Or lunacy?

Yesterday one of my dear skeptical colleagues sent me a link to a new article on lunar influences on plants (you can find it here).  Briefly, the authors argue that scientific evidence supports the concept of a lunar cycle influence on plants.  Interspersed within the discussion are references to seasonal and daily plant cycles, along with legitimate references to these verifiable phenomena.  (Had these references to circadian and diurnal rhythms been left out, the literature citations would have been rather paltry.)  Plants depend on these daily and seasonal cues for a variety of physiological and behavioral activities; lunar cycles have little obvious relevance to plants.  Nevertheless, “planting by the moon” is a belief system that has existed since ancient times.

This article is a great example of how pseudoscience insinuates itself with legitimate science.  Many of the references used as evidence for lunar effects on plants are of nebulous quality as they haven’t been reviewed by the scientific community; these include self-published books or lectures.  Furthermore, for every article that claims a lunar effect, I can find another discounting it entirely.  That being said, there are some legitimate papers indirectly linking lunar cycles with plant biochemistry.  Coincidentally, the lead author of one of these articles is a close friend and colleague whose research credentials are impeccable.

Here’s where the fascinating and complex nature of species interactions helps explain conflicting data.  Lunar cycles do affect certain species, including some herbivorous insects which are dependent on moonlight for feeding.  During the full moon, such insects feed more heavily and affected plant populations retaliate by altering the digestibility of their tissues. It’s likely that these biochemical changes have been erroneously attributed to direct lunar influence rather than herbivore defense.

To demonstrate direct lunar influence, one would need to study plants in an herbivore-free, controlled environment so that the only variable under consideration was lunar cycle.  Under such controlled conditions, would the same changes be noted over time if plants weren’t eaten by moon-managed insects?  Would you see changes if you modified the lunar cycle to make it longer or shorter (again without insects)?  Positive and repeated results would be necessary to establishing a role for lunar control.

As with so many other mystical explanations of natural phenomena, the real story is infinitely richer and more satisfying.

UPDATE: A peer-reviewed literature review on this topic has just been published. It’s well worth reading.

Friday geography answer

As several of our astute readers knew, the photo from Friday was taken on the west coast of the Salton Sea in California.  Specifically, it’s at Salton Sea Beach, a nearly deserted region that I managed to make more picturesque through careful photography.  Here’s another picture of the same beach:

There were few plants at Salton Sea Beach – a palm tree here and there – and only a few waterfowl like these pelicans:

The Salton Sea is really the Salton Sink – it’s a low area that has occasionally and naturally filled with water.  Given the high rate of evaporation in the region, the lakebed became highly saline over the centuries.

So what does this all have to do with a gardening website?  Well, the reason the Sea exists today is because of natural flooding combined with agricultural development.  Initially the Sea was seen as a boon to tourism, so spots like Salton Sea Beach and Salton City (near curiously named Squeaky Springs) became tourist destinations.  But as agricultural runoff began to change the nature of the Sea, fish populations failed and so did the tourism industry.

You can see the algal bloom where runoff meets the sea (check out this Google map here).  These desert valleys have been used for conventional agricultural production for many decades, and the results are seen in a sea full of fertilizers and pesticides.

In any case, a visit to the Salton Sea is both fascinating and depressing.  It’s well worth the effort.

Friday geography quiz!

Like last week’s, today’s quiz is a little different.  (I haven’t forgotten about last week’s question – just haven’t gotten a good answer yet!  Never fear!)  In any case, you know I spent some time in Palm Desert CA last week.  On one of our day trips, I took the following picture (we are looking east):

So here’s the question:  where are we?  (It was a day trip, so not terribly far from Palm Desert.)  You can ask questions that I may or may not answer.  Monday’s answer will tell you lots more about this “accidental” landscape!

Thieves purr

Today I found a cool website – it’s an anagram generator (http://wordsmith.org/anagram/).  The title of today’s post is the first of the 553 anagrams generated from the word SUPERthrive.

I’ve been getting free samples of SUPERthrive for a long, long time.   For those of you living on a remote desert island, SUPERthrive is a product invented and sold by “Dr. John A. A. Thomson (in 27 different title Who’s Who Directories),” according to one of the promotional flyers.  The same flyer features Nick Federoff (“ ‘Most Listened-to’ Radio Garden Expert”), who says of Dr. Thomson “he has saved far more trees than anyone else in the world.”

Space constraints and my patience limit how many of the product claims I can include.  Here’s one from the package:  “Dozens of the world’s science miracles in each drop!”  Well, what are these science miracles?  The only identified compounds on the label are Vitamin B-1 (which plants make themselves, and which I’ve written about here), and NAA, an artificial auxin used as a rooting hormone.   The rest are mysteriously referred to as “crystalline compounds of C, H, O.”

Since this product has been around since 1940, there should be plenty of documented research on its efficacy.  But thorough searches of the plant science databases turned up only two:  one on growing hydroponic orchids (where SUPERthrive is used as part of the experimental protocol but not as a treatment) and one on rooting stem cuttings of Intsia bijuga, an Indo-Pacific tree in the pea family.  Sadly, SUPERthrive was not as effective in promoting rooting as were traditional rooting hormones (IBA and NAA).  An online research report from TAMU found SUPERthrive to have no effect on cotton.  Even California Science Fair participant Chingiz R. Bigalimov was disappointed that SUPERthrive did not enhance rooting of narcissus bulbs.

Why would Dr. Thomson, who “by 1979 had received a Ph.D in biochemistry and nutrition, and a Doctor of Arts in biochemistry and horticulture,” claim that SUPERthrive is a “billions-proven extra-life-maker” without the science to back this up?   I tried to find more information on Dr. Thomson’s doctoral research at Columbia Pacific University (an unaccredited distance learning school in California), but it had been closed by court order in 2000 for, among other things, failing to employ duly qualified faculty and failing to meet various requirements for issuing PhD degrees.

I think all of us GPs would agree that if you like a product and it causes no harm, more power to you.  But please consider these last few caveats, especially if you are a Master Gardener or garden professional:

  • There is no established science supporting the use of SUPERthrive;
  • NAA is an artificial rooting hormone classified by the EPA as a pesticide, making SUPERthrive an unregistered pesticide.  Some states ban the sale of this product.

Think I’ll go play with the anagram maker some more…

Friday quiz – with a twist!

On our hike to Horse Thief Creek, I found this plant nearly ready to bloom:

But I have no idea what it is!  The area is about 3000 ft. in the Santa Rosa Wilderness.  I’ve checked all the wildflower books I have for these deserts and am not having any luck.  It doesn’t help that I can’t see the flowers, of course.

So take your best shots!  I’ll check out all the guesses and come up with a list of best possibilities.  Let’s see if you can help me learn a new plant.

Surviving the desert with beauty and efficiency

I’m away this week for an out-of-state seminar and a little annual leave.   Some of my favorite places to visit this time of year are the high deserts of California.  Today we hiked to Horse Thief Creek, a relatively easy trail in the Santa Rosa Wilderness.  It’s the perfect time of year to see the high desert in bloom, especially with last winter’s substantial rainfall.

In graduate school I became interested in environmental stress physiology, and I still am entranced by the plant kingdom’s ability to overcome nearly every environmental extreme on earth.  Desert ecosystems are particularly harsh, as rainfall is limited to a short period of time, often in the winter or spring.  While many perennials are able to tolerate the subsequent dry season, annual species cannot.  In essence, they escape drought stress altogether by existing only in seed form for most of the year.  Seeds contain relatively little water anyway, and are so protected against environmental extremes that they can remain viable for decades or even centuries.

But back to our desert.  After the rainy season, seeds of annual plants go into overdrive, germinating, growing, setting seed, and dying back all the span of a few weeks.  Thus, the lucky hiker can find an abundance of tiny, brilliant desert annuals when seasons and vacation schedules coincide.

Tomorrow it’s the Salton Sea.  Not sure what we’ll see in terms of plant life, but we’re hoping to catch some of the migratory waterfowl on their journey north.

 

 

 

 

Friday investigation – April Fools!

I didn’t exactly cheat on this one…but it was a mean trick nevertheless.

This is a contorted cultivar of Larix (can’t remember the exact name and I’m out of town this week), hence the twisty needles.  And indeed the tree is senescing.  The newer growth (the second flush of the season) just wasn’t as prepared for fall as the older growth, which is yellowing naturally.  So everything is just peachy with this tree.

Just goes to show you how important it is to know all the details when doing distance diagnosis!

 

Building healthy soils?

I love living in Seattle…but I’m getting increasingly impatient with the City’s “Building Healthy Soils” propaganda.  For years I’ve questioned their recommendation to perpetually amend landscape soil with organic material to no avail.  Let’s see what you all think of their “fact sheet” (which you can read here in its entirety).

“The best way to improve the soil is to add plenty of compost or other organic matter throughout the entire planting area before planting. Thoroughly mixing these materials deep into the soil helps provide water, air and nutrients to plant roots.”

Hmm.  No mention of how to determine IF your soil needs improving; without a soil test, you have no idea what your baseline organic matter level is.

But perhaps this recommendation is only for vegetable gardens and annual beds?  Nope.  In the next paragraph, we’re told to “Mix in organic material before planting lawns, perennials, trees and shrubs.”  We’re given helpful how-to instructions:  “Use a shovel or digging fork to mix amendments into the top 6 to 12 inches of soil. It is important to amend the entire planting bed — not just small holes for each plant. When planting individual trees and shrubs in lawns or existing beds, amend an area at least 3 feet wide, or 3 to 5 times as wide as root balls over 12 inches in diameter. Rototill large areas where digging is impractical.”

Now we’ve got a serious problem.  This practice is recommended for existing beds.  Not only will extensive digging or rototilling destroy any soil structure you might have, it will also take out the roots of any desirable plants in the vicinity).

But let’s continue to ignore reality and go on to the annual recommendations for adding compost to soils.
“Clay soils: 16 cu. feet (.6 cu. yard) = 2 inch layer of compost for new gardens. Use 1 inch per year in established gardens.”
“Sandy soils: 24 cu. feet (.9 cu. yard) = 3 inch layer of compost for new gardens. Use 1 – 2 inches per year in established gardens.”

Is the compost used as a mulch in these existing gardens?  No – the guidelines are prefaced with this instruction:  “Gardens: mix compost to 10- to 12-inch depth.”  (Can’t say this does much for promoting root growth either.)

This document shows a breathtaking lack of understanding of how landscapes function, especially over the long term.  It takes an agricultural practice (annual organic amendment of crop fields) and misapplies it to permanent landscapes.  It is devoid of the research which continues to show that improper soil amendment can cause serious problems such as soil subsidence, perched water tables, and nutrient overloads.  This last point is especially important to anyone living near aquatic ecosystems, since excess nutrients always end up in the water.

Before you plant this year, find out what your soil needs before amending it.  And remember that mulching is the natural (and sustainable) way to add organic matter to the soil.

Devious dandelions

As Austrian reader Johannes explained, the difference in dandelion flower height is due to herbivory – in this case from a lawnmower.  Dandelions are quite adaptable to variable environments (the phenotypic plasticity Johannes also mentioned) and flower heights will increase or decrease depending on these variables. This ensures that the flowers will be accessible to pollinators, yet not decapitated by lawnmowers.  It’s just one of the fascinating traits that make weeds successful!