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Can Fish Powder Poison Newly Transplanted Seedlings ?

Swamp Thang

Well-known member
Veteran
I copied and pasted this enquiry that I originally posted elsewhere on the net.

Hello fellow growers. I had some really healthy clones that were beginning to outgrow the plastic cups in which I started them out, so I decided to transplant them into slightly larger containers. Having recently read that fish meal is an ideal organic nutrient that breaks down very slowly over time, I mixed a fair amount of it into the soil that I added to the new larger containers, during the transplant of those seedlings. All these plants are under LED grow lights, with 18 hours light, followed by 6 hours of darkness. The intent was to transfer them outside in the next couple of weeks.

I was very careful to avoid shaking up the roots of the plants as I extracted each one from its cup, and gently seated it in the new container. After back-filling the new containers with my soil and fish powder mix, I watered the plants generously, expecting to see explosive growth over the next few days. To my horror, I checked those transplanted seedlings the next day, and every single last one of them was severely wilted, and clearly in the process of rapidly dying off. The remaining seedlings in their original cups, were thriving, so clearly I made a very serious mistake in my transplanting procedure. Oddly enough, I had previously used small amounts of fish meal and soil to top-dress ALL the plants in their original cups, with NO adverse effects at all.

Having transplanted seedlings from cups directly into the soil on numerous occasions in the past with no adverse reactions or wilted plants, my suspicion immediately focused on the addition of larger quantities of fish meal to the larger containers into which I transplanted these now dying seedlings. I used a fair bit of fish powder specifically because I had read that fish powder is a slow-release nutrient that is perfectly safe for plants at any stage of growth. Is this actually false, such that fish powder actually kills plants when added in larger amounts ?

This sudden wilting of 8 previously robust plants, immediately after transplanting into larger containers, just broke my heart, considering all the effort it took to create the clones, in a process that only runs about a 20% success rate for me, so this has been an enormous setback for my proposed outdoor grow this year. Any advice that will shed some light on this carnage, will be greatly appreciated by this complete noob to indoor seedling startups.
 

chilliwilli

Waterboy
Veteran
I think the large amounts of organic stuff in the soil that start to compost can make some ph swings and other problems. Let the soilmix sit for a while and keep it moist.
 

Swamp Thang

Well-known member
Veteran
I am definitely never going to add fish meal to young plants again. Because I had some weeks earlier added fish meal mixed with worm castings as top dressing for these same seedlings in cups, with the result that the leaves turned a darker green, I got lulled into a false sense of security, thinking that lots of fish powder would be even better for seedlings being transplanted.
 

rod58

Active member
sorry to hear your pain swamp thang ... i've done similar over the years but using fresh worm juice which i too thought would be safe .. nowadays i give them nothing ..
unless they ask nicely !!
 

Swamp Thang

Well-known member
Veteran
I hear ya Rod58. Now I know what it means to "love plants to death". Less is indeed more, as Buzzmobile pointed out. I'll pick up the pieces and chalk this episode down to lessons learned in the school of hard knocks. I'll try and make a few more clones from the surviving plants, and then start again using wiser methods, and keeping it simple.

For now, I'll allow all that fish meal to compost in a bucket, for use very sparingly later on after the transplant to my outdoors patch. I suppose the reason for my having no worries about using fish powder, is on account of my discovering that burying a whole fish alongside growing outdoor plants really boosted their health and growth rates. Now I know that powdered fish is entirely different from fresh fish, and is not suitable for young plants.
 

flylowgethigh

Non-growing Lurker
ICMag Donor
I tried the fish juice thing also but it was in response to fooling myself that I needed food in the soil. All it needed was to get the moisture right, and by adding moisture it needed along with the fish oil, they burned. Aloe, pH, cal-mag (I am under LED) when they need to grow roots is what I say to my self as I go in there thinking I need to water.

That fish trick works good when putting a plant into the ground.
 

Swamp Thang

Well-known member
Veteran
I tried the fish juice thing also but it was in response to fooling myself that I needed food in the soil. All it needed was to get the moisture right, and by adding moisture it needed along with the fish oil, they burned. Aloe, pH, cal-mag (I am under LED) when they need to grow roots is what I say to my self as I go in there thinking I need to water.

That fish trick works good when putting a plant into the ground.

When I buried a whole mackerel beside each of my my plants last year, I noted phenomenal growth and deep rich dark green color to the leaves. The final harvest was unlike any I'd seen before, and that very positive experience with fish soil amendment, was what led me to believe that ALL fish is good for plants, any time.

That assumption about all fish being good plant food, I now know to be wrong. I should never have transplanted all my healthiest plants in one go, because this basic mistake cost me all of the best specimens, leaving just the runts as survivors of the debacle. Good thing I didn't go the whole hog and ruin all my plants, or that would have been the end of thus year's grow season for me. I suppose the moral of this story is to try new ideas with one or two plants at most, and then go for the rest ONLY if there are no problems.
 

flylowgethigh

Non-growing Lurker
ICMag Donor
Or dilute new ideas 10-1and see the effects. I just put a tbsp of some stuff in my water reservoir (about 10 gallons), and it dropped the pH by a whole point. First time I have used pH ^.
 

rod58

Active member
i grow seedlings for a living , or fun ! thousands of vegetable seedlings and i make my own seed raising mixes and over the years
my mixes are getting more and more " bland " . originally i thought that a good , rich mix was the go but no more .
the trick is getting the roots to forage for the very small amounts of nutrients that is in the mix and then start feeding later on .
i do use seasol which is a plant health additive first up and once their at the first true leaf stage then the feeding begins .
don't be in a hurry ! and good luck with your grow ..
 

Swamp Thang

Well-known member
Veteran
i grow seedlings for a living , or fun ! thousands of vegetable seedlings and i make my own seed raising mixes and over the years
my mixes are getting more and more " bland " . originally i thought that a good , rich mix was the go but no more .
the trick is getting the roots to forage for the very small amounts of nutrients that is in the mix and then start feeding later on .
i do use seasol which is a plant health additive first up and once their at the first true leaf stage then the feeding begins .
don't be in a hurry ! and good luck with your grow ..

I wish I'd done some research in this forum before overdosing those seedlings with fish powder. These wise words of experience are much appreciated.
 

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