How to Make Natural Magnesium & Potassium for Plant Food

Things You'll Need

  • 5-gallon bucket with lid

  • Kelp meal or fresh sea kelp

  • Water

  • Mesh strainer

  • Additional bucket

  • Funnel

  • 2 spray bottles

  • Epsom salts

  • Measuring spoons and cups

All plants need potassium and magnesium to be strong and healthy. Potassium, like nitrogen and phosphorus, is one of the three primary macro-nutrients plants need. Magnesium is a secondary macro-nutrient, meaning that plants do not need nearly as much of it as they do potassium. You can use synthetic fertilizers on your plants, but doing so risks giving the plants too much of a good thing and has environmental impacts. Homemade, natural fertilizers are safer and less expensive to use.

Potassium Plant Food

Step 1

Fill the 5-gallon bucket with about 2 gallons of room temperature water. Add about a pound of sea kelp to the water and cover the bucket.

Step 2

Let the kelp steep for at least two days.

Step 3

Strain the kelp from the water by pouring it through the mesh strainer into the second bucket. Don't throw out the kelp; you can dig it into the soil in your garden or lay it on top of the soil for extra fertilization.

Step 4

Pour the kelp water into a spray bottle, using a funnel to prevent spills.

Step 5

Spray the kelp water directly on the leaves of plants to give them a foliar boost of potassium.

Magnesium Plant Food

Step 1

Pour 1 tsp. of Epsom salts into the bottom of the second spray bottle.

Step 2

Add 1 quart of water to the bottle. Put the lid on the bottle and shake it to dissolve the Epsom salts.

Step 3

Spray the Epsom salt water directly on the flower buds of pepper, tomatoes and other nightshades to encourage fruit set.

Step 4

Double the amount of Epsom salts to 2 tsp. per quart of water and spray on houseplants to fertilize them every month.