Friday fun, part 1

This posting is for Holly, who I am sure is desperately trying to finish her annual review.  I feel your pain!  And I’m going to add to it today.


The poinsettia in these photos is not from this Christmas, but from 2008.  You can see it thriving happily in its office environment.  I’m told by its caretaker Nick (a nongardener) that it has no bugs or other problems, and seems very happy.  And it’s blooming, without the benefit of the extended night period.  (The post-it notes are instructions to its care when Nick is away.)

Apparently SOME people can easily grow poinsettias well past their expected holiday life span.

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.

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!

Friday quiz

Thought we’d take a break from the invasive discussion (I have some throughts I’ll weigh in with on Mon.)  In the meantime, here’s a photo of dwarf Alberta spruce not too far from my boyhood home in Olympia, WA.  I get 2 or 3 of these calls each year; usually with a homehowner exclaiming, “I’ve got a tree growing out of my tree!”.

Friday puzzle solved!

Great discussion over the weekend, with some very astute observations.  If you looked at the brown needles under the tree in Friday’s picture, you may have noticed that some of them weren’t needles:

Not only was this tree planted too deeply, as several of you pointed out, but the burlap and twine were left intact.  It appears the nylon twine has already started to girdle the trunk, based on the trunk swelling just above where the twine is wrapped.

I’ve ranted about this practice already, so I’ll just sigh and move on to the first question – what directly caused the needle drop from the lower part of the tree?  It’s a young tree facing west so the lower half gets plenty of sunlight.  And though needle drop is normal with all conifers, the upper portion of the tree does not show the same drop with its interior needles.  My guess is that ethylene gas is responsible.

Plant roots under stress often release ethylene, a natural plant growth regulator more commonly associated with fruit ripening.  It also induces leaf drop, so as it percolates out of the soil it affects the lower leaves, but dissipates before it reaches leaves higher in the crown.  It’s a common phenomenon with over-watered house plants.

Thanks to all of you who participated in the diagnosis discussion – this is more fun than my 20 years of college teaching!

Friday fun!

It’s the holidays, but this pine tree is feeling anything but merry.  It was installed about a year ago.  While the upper foliage looks lush and green, the lower branches have no new needles and in fact the current needles are dropping:

This is a two part question:

1)  What might be directly responsible for the needle decline on the lower branches?  (Hint:  this is caused by the plant itself.)

2)  What might be the underlying stress causing the needle decline?  (Hint:  this is caused by by people.)

Additional photos on Monday will reveal all!

Friday puzzle answers!

Good speculation on the rhododendron leaf damage!  Jim in Wisconsin zoomed right in on the causes:  the first photo was taken on a year where we had an unseasonable freeze right as leaves were expanding, and the second was taken on a year where we had unseasonably hot weather as leaves were expanding.

In both cases, the ultimate cause of damage is lack of water in rapidly expanding tissues.  Once dormancy is broken, leaf and flower buds are highly sensitive to environmental extremes – they are expanding and are most sensitive to anything that interferes with water content.

During a freeze, leaf tissue water freezes, causing what’s called freeze-induced dehydration.  It’s not the ice that causes the damage, but the lack of liquid water in the cells.  Water freezes in the air spaces between cells, and osmosis draws water out of the cells into these intercellular spaces.  Eventually the cells more or less implode once they’ve lost enough water.

During a hot episode, the roots can’t keep the rapidly expanding leaves fully turgid, and again necrotic areas appear as a result of water loss through transpiration and cellular “implosion.”

So both of these problems are caused by a lack of leaf tissue water – and it’s impossible to tell from looking at them whether it’s from cold or heat or salt or some other stress that reduces water availability.

Bottom line:  keep track of seasonal abnormalities.  It will help you to correctly diagnosis problems that show up some time later.

Post-turkey puzzler

I hope everyone had a great holiday yesterday!  Since I am NOT a shopper, I’m avoiding “Black Friday” and posting another puzzle instead.

Consider this photo:

This is a rhododendron in my own landscape.  The photo was taken in July, though the damage on these new leaves occurred earlier than that.  In Seattle, rhododendron leaf bud break generally occurs in April.

Now consider this problem.  Same plant, different year – and actually a different problem!

So what caused this damage?

Explanations on Monday!