[Market-farming] Organic fertilizer in seed starting medium?

Shoemaker, William H wshoemak at illinois.edu
Fri Apr 8 20:50:38 EDT 2016

William H. Shoemaker

Retired fruit and vegetable horticulturist

University of Illinois

wshoemak at illinois.edu<mailto:wshoemak at illinois.edu>

From: Market-farming [market-farming-bounces at lists.ibiblio.org] on behalf of Marlin Burkholder [burkholders at glenecofarm.com]
Sent: Friday, April 08, 2016 7:41 PM
To: Market Farming
Subject: [Market-farming] Organic fertilizer in seed starting medium?

Looks like I have done it again!

A year or too ago I posted on MF about have trouble getting seeds started after mixing an organic based fertilizer (Plant Tone I think) into potting soil I was using for seed starting and for pricking week old seedlings over into grow out flats.  Plants would germinate satisfactorily, then stop growing.  After a week or two of wondering why the slow to no growth I would check a few seedlings and find few to no roots.  As I recall someone mentioned that plant proteins contained in some organic fertilizers can be toxic.

The first time it happened about five years prior to the time I last posted about it, I had used a premixed OMRI approved “ready to plant into” medium bought at a local garden center.  Every thing I planted into that stuff failed and I got my money back when I went back to the garden center and bitched.

The time I used Plant Tone I mixed according to instructions on the bag, about a 1/2 to one cup into about a cubic foot of medium.  I assumed that organic materials are more forgiving of less than precise mixing procedure but apparently got bit.  Last year I decided for the next go round to use nothing but chemical salt based materials, Miracle Grow or something similar, and got along better.

Well guess what!  I succumbed to temptation again and bought a five pound bag this spring to use in my starting mixes.  You know, it had kelp, bone meal, alfalfa meal, fish meal, micorizae, several other beneficial organisms whose names I can’t remember etc.--all the good stuff, along with the promise that the plants would love it!  When two seedling flats of peppers tanked, I blamed it on a small amount of germination mix I had left in an aluminum baking pan for about a week which I had used to cover seeds.  The one I had covered with material other than what was in the aluminum pan did not have impressive germination, but the seeds that did come up were healthy.  Then the tomato seedlings I had pricked over into to grow out flats started to go down hill.  A watering with Miller’s Nutri Leaf didn’t revive them.  This afternoon I repotted 180 plants into clean potting soil watered with nothing but Nutri Leaf.  I will do the other half of my tomato seedlings on Monday and hope for better luck.  After over 20 years of plant starting this thing is getting embarrassing and extremely frustrating.

Is it wrong to use fertilizer in seed starting mix?

Marlin Burkholder

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