Plants wilted

I made a planting mix of compost, perlite and peat and added a blended dry organic fertilizer balanced for growth (as directed). I watered when the soil felt dry two inches below the surface. The plants were doing pretty well, but my friend said he accelerated his plants’ growth rate by fertilizing with fish emulsion fertilizer. I added the fish emulsion to the water once a week. A few hours after the third time I fertilized, the plants all started going limp.
I brought them into my bath tub and ran water through the containers. All 10 survived but they all lost leaves to a varying degree. What happened?

Jessie J,

Montreal, Canada

The plants almost died from over-fertilization.

One of the laws of physics is that a concentrated solution draws water from a dilute solution. Plants draw water from the soil by maintaining a higher level of dissolved salts than the surrounding medium. When you added the third dose of fertilizer the concentration of dissolved salts in the planting medium exceeded the concentration in the plants. The soil drew water from the plants, causing the wilt.

When you ran water through the containers some of the soluble fertilizers drained away. This lowered the concentration of the solution in the planting medium. The solution in the plant was once again more concentrated, and the plants could draw water once again.

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