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Seaweed / Kelp Fertilizer: Complete Guide

Oregon State Extension

A micronutrient-rich organic supplement made from kelp or seaweed. Very low NPK but packed with trace minerals, growth hormones (cytokinins, auxins), and amino acids. Best used as a supplement alongside primary fertilizer.

Key Facts

1N
0.5P
2K
N 1% Nitrogen: leaf and stem growth
P 0.5% Phosphorus: roots and flowers
K 2% Potassium: health and disease resistance
Learn more about NPK
NPK Ratio
1N
0.5P
2K
N 1% Nitrogen: leaf and stem growth
P 0.5% Phosphorus: roots and flowers
K 2% Potassium: health and disease resistance
Learn more about NPK
Formliquid concentrate
Application Rate1-2 oz per gallon of water as foliar spray or soil drench
Price~$6/lb est.
Release Speedslow
Burn Riskvery low
organicliquid concentrate

What is Seaweed / Kelp Fertilizer Best For?

all plantsstress recoverytransplant shockroot development

When Should You Use Seaweed / Kelp Fertilizer?

Use as a supplement for stress recovery, transplant shock, root development, and overall plant health. Safe for foliar and soil application.

When Should You NOT Use Seaweed / Kelp Fertilizer?

Not a standalone fertilizer. NPK is too low to meet plant needs alone.

Source:Oregon State Extension