How to Make Effective Use of Seaweed-Based Plant Food

Seaweed-based plant food typically comes in either a liquid form or a dried form. The fertilizer is organic and has naturally high levels of copper, iron, boron, zinc and manganese, which are all good supplements for soil. Seaweed plant food is applied either as a spray or sprinkled over the surface of the soil. However, gardeners must use caution not to overapply it, since the fertilizer will stunt plant development in excessive amounts.

Things You'll Need

  • Fertilizer spreader
  • Granular seaweed fertilizer
  • Tiller, rake or hoe
  • Water
  • Garden sprayer
  • Liquid seaweed fertilizer


  1. Granular Application

    • 1

      Monitor the ground in the planting area starting in the early spring to determine when it thaws completely. Plan to apply granular seaweed plant food as soon as the ground is workable so that it breaks down enough in time for planting.

    • 2

      Fill a fertilizer spreader with 1 pound of seaweed-meal plant food for every 100 square feet of planting area. Push the spreader over the area to apply the seaweed. If you are applying it to a preplanted bed or smaller area, simply sprinkle it over the soil evenly using your hands.

    • 3

      Work the seaweed plant food into the soil using a tiller for unplanted areas or a rake or hoe for those with plants.

    • 4

      Water the soil to a 3- or 4-inch depth to begin dissolving the seaweed into the ground.

    Foliar Spray Application

    • 5

      Open a garden sprayer and fill it with 1 gallon of water and ¼ tablespoon of liquid seaweed concentrate.

    • 6

      Close the sprayer and shake the tank for 30 seconds to mix the solution.

    • 7

      Spray the seaweed plant food on all stem and leaf surfaces of the plants until they are saturated.

    • 8

      Open the sprayer after all leaves are wet and pour any remaining liquid into the soil at the base of each plant.

    • 9

      Repeat the foliar spray every two weeks throughout the remainder of the growing season.

Tips & Warnings

  • If desired, you can also add seaweed-based plant food to your compost pile to supplement it prior to placing the compost into your garden.
  • You can also soak seeds in liquid seaweed fertilizer for 20 minutes prior to planting to enhance their germination and growth.
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  • Photo Credit David De Lossy/Photodisc/Getty Images

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