Updated: January 23, 2020
The most common reason why gardeners fail with raising seedlings indoors is the dreaded dampening-off.
Cruelly, it strikes in the early stages causing the stems to shrivel and the young seedlings to topple over and die. One morning you wake up and your plants are no longer upright.
The cause is a microbial imbalance that allows a plant pathogen, frequently Pythium ultimum, to infect the plant.
After pondering this for a while, a thought occurred to me. Garden diseases result from imbalances of one kind or another. Is that the cause with dampening-off?
If true, what if I could use compost tea to maintain microbial balance? Would this reduce the chance of dampening-off.
Typically, gardeners use compost tea to increase the number of good microbes and create a balance between good and evil. So then, why wouldn’t compost tea work to improve overall seedling health and provide protection from dampening-off pathogens?
Let’s take a sec to get the legal words out of the way. This article may contain affiliate links. That means if you click and buy from my partners, I will make a tiny amount of money. This in no way affects my recommendations.
Grass is always greener under the compost tumbler
My interest in compost tea first started when I noticed that the grass under my compost tumbler grew lush and green. The rainwater washed through the composter and created a great plant elixir.
My wife heard me marvel at my unintended success with growing grass under the compost tumbler and bought me the necessary equipment for a homemade compost tea brewer for my birthday.
I supplied the very finished, homemade compost.
Now there’s a sexy birthday gift!
Brewing compost tea
Compost tea recipes are very easy to follow:
Step 1. Mix mature compost with water.
Step 2. Add food (molasses) for the microbes.
Step 3. Incubate while adding air to the liquid for 24 hours.
You’ll need to use a fish tank air pump to pump air into the solution. The hope is that the the good microbes exponentially multiply in this ideal environment
Here is a video from organic gardener Howard Garret that shows how it’s done:
A while back I used my new birthday gift to brew up a couple batches of tea. Then, I applied it to my plants in the garden.
The funny thing was that I didn’t see much if any improvement. I used it for both foliar feeding and as a soil drench, as the experts recommended. I chalked up the lack of success to the original compost not being “hot” enough with microbial activity.
Although it didn’t much help with my mature plants, it might still help with my seedlings. Right?
Compost tea on seedlings
It turns out that a 2004 study conducted by researchers from Oregon State University and the USDA Agriculture Research Service looked specifically at using compost tea on seedlings. The question they looked at was: Can you use tea to ward off dampening-off.
Unfortunately, the study results are no longer available. I suspect that someone lobbied to remove it from the Internet.
The researchers conducted the study on cucumber seedlings that had been intentionally infected with Pythium ultimum. They tested a number of types of compost made from a variety of original materials as well as a number of tea additives. Their testing methods used some of the best equipment possible to see if any of the teas would consistently suppress dampening-off.
The study showed that only compost tea made with the additives of kelp and humic acid were shown to consistently reduce dampening-off. None of the other formulations worked consistently.
The more startling conclusion was that tea made with molasses “inconsistently suppressed damping-off.”
This probably had to do with the residual molasses that was in the tea, which could have actually feed the pathogens. Also, the study concluded that diluting the compost tea, often recommended for seedlings, reduced any positive impact from the formulations.
Although many backyard gardeners can brew a good batch of compost tea, few can recreate the exacting methods required for success with dampening-off and seedlings.
More specifically, I would use your compost tea on mature plants and not on seedlings. And, even with mature plants, expect inconsistent results.
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