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Old May 16, 2017   #13
Cole_Robbie's Avatar
Join Date: Jun 2012
Location: Illinois, zone 6
Posts: 8,206

The organic matter in those fertilizers is there to feed bacteria. In warm weather, it is the beneficial, aerobic bacteria that grow. But in cold weather, anaerobic bacteria like pythium take over. I get stem rot, mostly from fish emulsion. Using any mix that contains worm castings, like Light Warrior, and letting the plants get below about 50 or so, especially when in six-packs, will make them turn yellow and purple, and become permanently stunted. Microdwarfs and PL varieties seem to get it the worst. I toss out several flats of plants every season due to these problems.
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