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"And the LORD God made ... trees that were pleasing to the eye ..." Gen. 2:9, New International Version.

"Bonsai isn't just something I do; it's part of what I am." Remark to my wife and daughter.

Thursday, June 28, 2012

Indiana, or the Gobi Desert ... ?

     Yes, this post's title does contains some hyperbole; but it's not just hyperbole. Our front lawn looks typical for this part of Indiana right now: brown and dry. The grass blades crunch underfoot. One neighbor takes the time to move a sprinkler around his yard at least once a day; but otherwise, the lawns in the neighborhood are faring no better than ours.

Only the weed grass (lower left) is really thriving!
Neighbors' lawns have gone dormant too.
We've had unusually hot and dry weather for over a month. Today's temperature topped out at 88° F (31° C.) Tomorrow's expected high is 100° F (38° C,) a psychologically significant marker. Summer temperatures above 100° F are nothing new here, but they usually come later. If the heat does get that severe tomorrow, it will the first time for that to happen this early in the year, in the 37 years I've lived here.

Addendum, the following day: today's high was 104° F (40° C,) at 3:45 PM. I believe that's a new local record for the date.

Serissa shoots like this one alert me when extra waterings are needed.
More significant for gardening, bonsai and otherwise, is the lack of rain. Since the beginning of June, we've had four (count 'em, four) days with measurable precipitation. The rainfall on those days added up to a total of .08 inches; not even a tenth of an inch. Like my neighbor with his lawn, I've been putting a lot of effort into watering my trees!

But even a drought can yield unexpected good. I've discovered that serissa (Serissa foetida) has a characteristic that is very useful in dry conditions (but that must be used carefully.) Its non-lignified shoots -- the ones that aren't yet woody -- begin to wilt and droop rather quickly when the plant starts to dry out; before the leaves of anything else I grow. But once the tree is watered, they perk right back up, and without any permanent injury that I have ever observed.

So, serissa has become my "tell-tale" plant, a botanical equivalent of the proverbial canary in the coal mine. It goes without saying that I try not to let anything get to the drooping stage in the first place. But sometimes a day is hotter than expected, or interruptions arise. Any more, when I'm outside in hot weather and in view of my serissas, I glance at them from time to time. If their green shoots are starting to droop, I know I need to water immediately, whether I had expected to or not!

Gmelina philippinensis, a woody climber like bougainvillea.
The quick and full recovery of serissa shoots contrasts with the responses of another plant I grow: Gmelina philippinensis, called "parrot's-beak" from the flower shape. The foliage of Gmelina (the "g" is silent) droops almost as quickly as serissa shoots, but doesn't recover as well. A green shoot on a parrot's-beak that wilts enough to hang limp is probably a goner.

(I know some of you are wondering: the brown moss in the picture is left over from the Fort Wayne display in May; it's serving as a temporary mulch.)

Which brings up a distinction worth mentioning. I know the terms "drought resistance" and "drought tolerance" are often used interchangeably; but I once read a differentiation between the two, and I think it's useful.
  • Drought resistance: the amount of drought a plant can take before it starts to show outward signs of distress, such as wilting foliage or scorched leaves.
  • Drought tolerance: the amount of drought a plant can take before most or all of the plant dies.
There are two thing to keep in mind about these limits. First, they vary from species to species. I've given an example above: serissa wilts more quickly than parrot's-beak. Second, the interval between them also varies from species to species. Some plants wilt quickly, and die quickly after that. Some wilt quickly, but then hang on for quite a while before succumbing. And some plants resist wilting for a long time; but by the time they do wilt, they are at death's door. Needless to say, it's helpful (it might be critical someday) to know just how the species you grow react to drought -- both their resistance and their tolerance.

It's surprising, sometimes, the knowledge that can be brought to light even by a drought.

:-)  :-)  :-)

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