02 January 2013

Salt Damage or, an Abiotic Pathogen

Let me explain this post:  I was planning to write about salt damage in houseplants after reading about it in The Ortho Problem Solver book.  We had another instance of salt damage brought to us by someone as well.  During the continuing education class I just finished, there was opportunity for me to write about the same topic in regard to abiotic pathogens.  When I finished writing that one, I noticed that I had already written a completely different post about salt damage.  So here you go - two for one.

One day at the Master Gardener's office I was looking through a book that some mentors recommend - The Ortho Problem Solver.  It's a very large book, and a little overwhelming if you aren't looking for something specific.  I wasn't looking for anything specific, but at least I was concentrating on houseplants.  I started noticing that one symptom kept coming up - leaf tip burn.  It seems to be common in houseplants and there are a couple of causes.

Leaf tip burn is actually a drying out of the tips of leaves, because they are not getting enough water.  Sometimes it's caused by not watering enough or the humidity is too low, but there is a more common reason that most people don't realize - salt damage.  In order for them to stay healthy, we need to fertilize houseplants, anything in pots, because they cannot use their roots to find nutrients on their own.  Fertilizers are mostly salts that are dissolved in water and taken up by the plants, but when there are excess salts, they can burn the roots.  This keeps the roots from taking up enough moisture to feed the entire leaf, resulting in leaf tip burn.

So what can you do?  There are a number of things.  Don't over-fertilize - this will cause a higher buildup of excess salts that may cause damage to the plant.  Another option, and probably something you should do anyway - even if you don't fertilize too much - is to flush the excess salts out of the potted plant.  Water heavily, letting the water drain from the pot - after letting it sit for awhile, repeat again.  Some plants may need a third round of flushing to get rid of most of the salts.

So, keep this in mind when you bring your plants in for the winter.  You may want to make it a part of your plant maintenance, flushing them in the spring when taking them outside in the spring, and the same thing when bringing them inside for the winter.

In this Master Gardener recertification / continuing education course I’ve been taking this month, one of the topics we’re studying is plant pathology - specifically plant pathogens.  What is a plant pathogen?  It is “an organism or an agent capable of causing a disease on a plant.”  There are different types of plant pathogens: biotic and abiotic.  Biotic pathogens are infectious living organisms capable of reproducing and spreading.  Abiotic pathogens are non-living, non-infectious - they cannot reproduce or spread.  It is the latter that I want to talk about today.

Abiotic pathogens tend to be a case of extremes - too much or too little sunlight, moisture, fertilizer, too high or too low of a temperature.  We had an interesting case at the Master Gardener’s office recently involving an abiotic pathogen.  A woman came in with numerous leaf samples from her landscape - most of the leaves had brown, dead edges.  She was very concerned, because this was happening all over her yard.  My first thoughts were either that her yard needed more watering or it could be salt damage, but I’m still new at this, so we started asking her questions.  She said everything was fine when she moved in two years ago.  They watered plenty, using water from a well.  Here was a clue - she lived very near a brackish creek, and if her well was not very deep, she could have salt water in her well.  So we were betting on salt damage as her problem, but we had an agent confirm this.  We think the previous owners probably discovered the high salinity of the well and stopped using it.  Not knowing about the problem, the new owners began using it again when they moved in, which caused this problem - too much salt.

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