Pigmented Mulch in Paradise

Just back from a quick vacation to Little Cayman island.  Truly a dot on the map – the whole island is about 7 miles long and a mile wide. Only 150 locals and a couple hundred tourists are on island at any one time.  It’s beyond laid back, with few attractions other than the resident iguanas and red-footed boobies (booby jokes abound).

Airport terminal/post office/fire station.

The big draw is diving – LC is the home to Bloody Bay Wall, one of the most famous dives in the Caribbean.  The reef drops off like a sheer cliff, from 40-60′ to more than 1000′.

All the action is underwater!
(Let me know if you want to see more slightly blurry diving photos.)

“Fascinating, Holly.  But what does this have to do with painted mulch?”

The extent of the landscaping for most yards: conch shells arranged in interesting designs and/or piles. But as we pedaled past a rather upscale condo, I came to a screeching halt. A gorgeous Bismarckia nobilis had caught my eye, but then I saw what was under it. Egad.

Everything comes to Little Cayman by a weekly barge or little prop plane and is wildly expensive. Four-pack of batteries? $15. A six-pack of beer is $20. TWENTY DOLLARS!!!

So, good readers, what we have here is possibly the most expensive mulch on the face of the earth. I can’t even imagine.


Need a lift?

One of the topic groupings for our posts is titled ‘Cool research’.  The subject of today’s post has actually been around for a few years but I still think it’s pretty cool.


When we think of interactions between plants we usual think of negative interactions such as competition for water and nutrients or maybe allelopathy.  But there are cases where plants can benefit each other.  One of these is a phenomenon known as hydraulic lift.    Hydraulic lift is the passive movement of water from roots into soil layers with lower water potential, while other parts of the root system in moister soil layers, usually at depth, are absorbing water.  In essence, plants will large, deep root systems (usually trees) bring soil water from depth to the surface where it can be used by other plants.  Hydraulic lift has largely been observed in arid and semi-arid ecosystems, though it can occur in wetter systems as well.  For me, the research that went into discovering hydraulic lift is as fascinating as the process itself.


One of the key lines of evidence for hydraulic lift comes from studies of stable isotopes.  As you may recall from college or high school chemistry, atoms of each chemical element have a certain number of protons and neutrons, which give it its mass.  A small portion of each element has extra neutrons resulting in a ‘heavy isotope’.  In the case of hydrogen, approximately 1 in 6400 atoms is heavy hydrogen or deuterium (2H).  Interestingly, the amount of 2H in water can vary depending on the source of the water; this ratio is termed an isotopic signature.  By comparing the isotopic signature of ground water and rain water in a given location, researchers can actually tell where certain plants are getting their water.  One of the classic studies in this area was conducted by Todd Dawson at Cornell in the early 1990’s.   Dawson analyzed isotopic signatures of groundwater, rainwater, and water in various plants around sugar maple trees and determined that many herbaceous plants contained a high proportion (up to 60%) of groundwater.  But how do shallow-rooted plants obtain groundwater?  The neighboring maple trees bring it to the surface from ground water as they are hydrating overnight.  An efflux of water from the maple roots results in a localized increase in soil, which can be utilized by other plants: hydraulic lift.


How important in hydraulic lift in most landscapes?  Probably not very.  Demonstrating significant hydraulic lift requires the proper hydrology (shallow ground water accessible to trees or shrubs but not smaller plants) and limited rainfall.  But the importance goes deeper (no pun intended!).  Prior to the advent of stable isotope techniques, many would have been dismissive of the concept of hydraulic lift.    Since 1993 over 100 papers have now been published on the subject.  To me, the ultimate value of Dawson’s work and related studies is showing the importance of keeping an open mind and being receptive to new ideas. 


Why bother having trees?

Sorry to be late with my post this week – I was away reviewing grant proposals.  It was interesting and useful work, but really drains your brain.  So with that being said, my post is long on pictures and short on words.

One of the things that bugs us GP types is poor plant placement.  Why bother planting a tree if you’re not going to allow it to grow naturally?  Here are some photos to mull over the weekend.  While I have lots of bad pruning pictures, these ones are chosen specifically because the trees were obviously poor choices for either site usage or size.

Because my sense of humor seems to have been left at the grant reviewing venue, I can’t think of amusing captions for these pictures.  But I’ll bet you can!  Just submit them in the comments sections, and I’ll repost the photos later next week with your contributions.

Photo #1

Photo #2

Photo #3

Photo #4

Photo #5

Balanced Fertilizer and Peak Phosphorus

When I first started reading extension recommendations for plants around 15 years ago now, I read a lot about “balanced fertilizers”.  Today I still see balanced fertilizers recommended, but not nearly as frequently, which is a good thing.

At this point you may be asking yourself “what is a balanced fertilizer?”  A balanced fertilizer is one that has three numbers on its label which are the same — such as a 10-10-10 or a 14-14-14 (Nitrogen, Phosphorus and Potassium are the three nutrients indicated by
these numbers).  Although it might seem like equal numbers would mean equal amounts of these nutrients, these numbers actually indicate percent Nitrogen, percent P expressed as P2O5 (in other words, if you took all of the phosphorus present in the fertilizer, made it into P2O5 and then added it back to the fertilizer and figured out what percent of the fertilizer that made up — that would be the second number) and percent potassium expressed as K2O (basically the same as the phosphorus example you saw previously).

But here’s the problem.  The amount of phosphorus, and often potassium, that is added when you use a balanced fertilizer is typically out of line with the amount that the plant needs.  This is because fertilizers are usually applied based on the amount of nitrogen that a plant needs.  The reason that a balanced fertilizer was usually recommended was that phosphorus and potassium levels in these fertilizers is high enough that they provide all of those elements that a plant needed without being toxic to the plant.  The problem is that, while the levels of these nutrients added might not be toxic, they are in excess of what is usually needed.

OK, so we’re adding excess phosphorus and potassium, what’s the problem?  Well, for the potassium the problem isn’t usually that big a deal.  In fact, a fertilizer bag with the first and third numbers equal may be what’s called for in many cases — fruits and nuts in particular often like a higher level of potassium.  Additionally, the world has a pretty big store of potassium so we’re not likely to run out any time soon.  Phosphorus, on the other hand, is a little bit different.

Phosphorus is a bit more hard to find in large quantity than either of the other elements in a bag of fertilizer.  Because of this it is often the element that limits the growth of plants, for example algae.  When phosphorus runs off into a lake or other body of water it can allow algae to go crazy and use up all of the oxygen in the water killing fish and other creatures (actually it’s the dead algae that do this — bacteria use oxygen while breaking the algae down).  Most of you are familiar with this and know that it’s the reason why Minnesota and now Wisconsin have banned the use of phosphorus fertilizers on lawns without a soil test.

But here’s what you may not know.  Most of the phosphorus which we use for fertilizers comes from rock phosphate.  Rock phosphate is mined in only a few places around the world, Florida being one.  Just as it is a foregone conclusion that we will run out of oil someday, it is also a foregone, but lesser known, conclusion that we will run out of rock phosphate.  Estimates are that we will reach “Peak Phosphorus” (in other words maximum phosphorus production.) in 20 years or so and that we will run out in 50 – 100 years.  Here’s an interesting article on the situation  http://www.foreignpolicy.com/articles/2010/04/20/peak_phosphorus

So conserve our natural resources and skip the balanced fertilizer.  When asked for a general use fertilizer recommendation I usually recommend something with a ratio of roughly 5-1-2, with a higher potassium content if you’re growing fruits or nuts.

Restoration ecologists – you need us! Part 2.

Last month Linda posted on the need for horticultural knowledge for those trying to restore native habitats or at least establish native plants. There seems to be a pervasive notion that if we plant natives all we have to do is stick them in the ground and walk away. They’re native, right?  Don’t need irrigation; don’t need fertilizer; all that good jazz.   Well, often there is lot more to it than that.


A case in point.  Over the past couple of years I’ve been watching an unintended experiment near the State Capitol grounds in Olympia, WA.   The State opened up a vista so that the south end of Puget Sound and the Olympic Mountains were visible from the Capitol campus. It’s a lovely view.   As part of the development, a switchback trail was established on the steep hillside to connect the Capitol grounds with the park surrounding Capitol Lake below. A great idea.  Along the trial the hillside was planted with an array of native plants such as Oregon grape, salal, alder, and western redcedar.  Another fine idea.  Now comes the problem.  Near as I can tell, there was no plan for maintaining these native plants.  In fairly short order the hillside has become overrun with grasses, dandelions, and Himalayan blackberries – not exactly the desired effect.  And therein lies the rub.  Everyone is on board to plant natives but who’s on board for the hard work to maintain them.  Keeping weedy species from this planting by hand would take an army volunteers.  Burning is likely out due to the proximity of the Capitol and probably wouldn’t promote the desired species.  The answer?  Most likely a combination of hand-weeding and herbicides.  It is interesting that when the end justifies the means, herbicide is not such a dirty word anymore.  So there you go.   In order to effectively establish and maintain native plants, not only do we need to know about Mahonia aquifolium, Gaultheria shallon, and Alnus rubra; but it also helps to know about glyphosate, flumioxazin, and triclopyr.

Icky Friday puzzle solved

OK, now we know why we usually leave the puzzles to Linda: mine are too easy!  As several folks correctly noted the photo in my yard was an example of the "dog vomit fungus" or, more correctly "dog vomit slime mold" Fuligo septica.  Either way, it’s fairly disgusting and fairly common.  My expereince has been it that it often shows up shortly after I lay dowm some fresh mulch (ground pine bark in this case) and then we get rain and warm temps.  Although sometimes it shows up when I give our dogs too many treats… Hmmm…

Thanks to all those who chimed in with comments and links.  Here’s one more link with some interesting tidbits.

Almost But Not Quite

Today I was reading an interesting gardening website with a wide variety of advice, some good and some not so good.  As I analyzed the website in my mind to figure out why some stuff was good and some stuff was bad it occurred to me that the problem was that a lot of the stuff that the author was recommending was based on testimonials.  And then it occurred to me that many of you out there might not know what a testimonial is and why recommendations based on testimonials shouldn’t be recommended — and then viola! I had a blog post.

A testimonial is testimony presented by one person about their experiences with something.  It’s like when a friend tells you that dryer lint controls slugs in a flowerbed. Don’t laugh, this is a real suggestion on one website!  This person decided that it was appropriate to put dryer lint around their garden, and when they did, slug damage appeared to be reduced.  Good for them.  But is it good for you?  The answer is maybe.

The problem is that this person is missing the two things that we need when assessing whether a particular thing works.  First, we need a a control, and second, we need replication.  Let’s use the dryer lint example.
We have no idea whether, if we hadn’t put out the dryer lint, the slug population might not have dwindled anyway.  To find out whether it might have we need to treat only a portion of our garden with dryer lint and then see if the treated portion has more or less damage than the untreated portion after a few weeks.  The untreated part of the garden is called a control and it is necessary for a good experiment.  But it isn’t the only thing necessary for a good experiment, so is replication.

It is possible that the part of the garden which was treated with the lint had less slug damage than the control portion of the garden for some reason besides the lint — for example, perhaps the area where the lint was applied happened to be further from the sprinker than the other section — and slugs like it moist.   So to combat possible problems like this you need to conduct your experiment more than once.  In other words, you need to replicate your trials.  This might be done by doing this experiment over multiple years, by having other people in your gardening club try it too, or by dividing up sections in your garden into six or so equally sized sections so that three randomly selected sections get treated with lint and three don’t.  Or, best of all, do all of these things — multiple years, multiple gardens, and multiple plots within a garden!  If we did more testing like that I have a funny feeling that we’d have fewer crappy products for sale.

Testimonials are interesting, but don’t get fooled into thinking that they prove anything.  They don’t.  You need control and replication to demonstate that something really works.