Toxic Seed Starting Flats?

gleneco1 at gleneco1 at
Sun Mar 17 20:42:39 EST 2002

I tried to post a series of communications I recently had with the
Winstrip company concerning some problems I have been having with
starting seeds in some of their flats.  The post was too long so I am
breaking it up into several parts and posting again.  There is some
revealing information here.

Marlin Burkholder APS

I have been having some more problems this year with poorly growing
seedlings in reusable molded flats which I had purchased from the
Winstrip company.  I am forwarding a copy of my original inquiry plus
their reply (with their permission). 
Dear sirs:

Last year prior to the plant starting season I soaked all of my seed
starting trays, including my WINSTRIP trays,  in 5.25% sodium
hypochlorite (Clorox) solution diluted 9 parts water to 1 part Clorox in
order to sterilize them.  This was done according to directions I had
repeatedly heard from gardening experts.  The only mistake I may have
made was to leave the flats soaking in the solution for several days
instead of the 15 minutes I have since heard would have been sufficient
to sterilize them.  I had also heard that sodium hypochlorite in solution
breaks down and loses it's germicidal properties within 30 minutes of
exposure to soil particles and or sunlight.  For this reason I didn't
think there was any harm in leaving my flats to soak for an extended

Nearly everything I planted in the sterilized flats did poorly last year.
A typical pattern was that seed which had been planted would germinate,
send up it's first set of leaves, and stop growing.  After a week or more
of waiting and finally wondering why they weren't growing, I would pull
up a few plants and find few or no roots.  Onions, lettuce, and cabbage
plants were most seriously affected.  Tomatoes and peppers were seriously
set back but recovered eventually when I transplanted them out into newer

I had some of this type of problem the year before and always blamed it
on other things like keeping my soil medium too wet, using carried over
planting medium, and contaminated flats, hence the renewed effort last
year to get everything squeaking clean.  I even continued thinking my
problems were caused by other things well up into the growing season
until I read a warning in "Growing for Market" magazine that using sodium
hypochlorite to clean equipment can cause problems.

After the seed starting season was over, I immersed all of my WINSTRIP
trays in a free flowing spring reservoir and left them there for several
months.  Then I scrubbed them down as best I could and left them outdoors
exposed to the elements for the remainder of the year.  Despite all the
efforts to purge them of possible chemical contamination, a white film
persists on parts of some of the trays. I am inclined to think this is
probably hard water lime deposits and nothing to be overly concerned

I started planting again this season optimistic that things would be OK
but all of the onions planted in WINSTRIPs have failed and the lettuce is
not looking good.  Cabbage seems to be growing normally but the broccoli,
though looking healthy now, has not grown past the primary leaf stage and
could be in trouble. Once again the classic symptoms are there: alive but
poorly growing plants with weak roots.  I have both lettuce and onions
now planted in media and containers which have never touched anything
that has ever touched chlorine compounds and will know within a week how
their growth is comparing with my other plantings.

Has anyone in your company ever looked into the possibility of chemical
contamination of the plastics used in your product?  I would be
interested to know the chemical composition of the plastic used in your
trays and whether or not chlorine compounds could impregnate this
material in such a way as to interfere with plant growth a year or more
after the initial contamination had occurred.  If this has indeed
happened, is there a more effective way to purge the flats of this
contamination?  If I have to throw out my WINSTRIP trays, this will be a
considerable economic loss.

Looking forward to your response,

Marlin Burkholder

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