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11 Benefits of Seaweed Fertilizers and How to Use It

I have studied organic gardening for 60 years and raised many large gardens. I have read Organic Garden Magazine most of my life


1. Seaweed Used for Centuries to Fertilize Garden Soil

2. Benefits of Seaweed Fertilizers

3. How to Use Seaweed Fertilizers

4. Patio Container Gardening

5. Different Preparations of Seaweed Fertilizers

6. Conclusion: Many Good Benefits to Seaweed Fertilizers

Seaweed has been used as a fertilizer in different parts of the world for centuries.

Seaweed has been used as a fertilizer in different parts of the world for centuries.

Seaweed Fertilizer Is Not New

The use of seaweed in the garden soil is nothing new. In fact, seaweed as a fertilizer has been around for centuries. Dulse and kelp have been used on the west coast of Ireland since before the thirteenth century. It has also been used in past history in the Channel Islands, Scotland, and the Falkland Islands. For good reason, too. There are many benefits to using seaweed as a fertilizer.

Benefits of Seaweed Fertiliser

Seaweed Fertilizers benefit your garden harvest in many ways because of the many nutrients, trace minerals and natural plant hormones in seaweed.

1. many fruits become sweeter

2. veggies are less prone to softening and often grow larger

3. increases the number of flowers on flowering plants

4. increases plant resistance to disease

5. cut flowers stay fresh longer

6. encourages root growth, both in rate and mass

7. fruits and veggies survive longer post-harvest if treated with seaweed pre-harvest

8. seaweed has more than seventy trace minerals and ready to use nutrients

9. contains hormones to encourage plant growth

10. discourages pests

11. there is no evidence of problems with salt from seaweed like when sea salt fertilizers are used improperly.

How to Use Seaweed Fertilizer

Seaweed fertilizer can be used in many different ways.

1. As a seed inoculant, liquid seaweed fertilizer increases and accelerates germination, and enhances the rapid development of a healthy root system. Soak the seeds in liquid seaweed fertilizer overnight before planting. Use a solution of two ounces of liquid seaweed concentrate in a gallon of water.

2. To decrease transplant shock, spray the roots with liquid seaweed before transplanting. Use a solution of two ounces of liquid seaweed concentrate in a gallon of water.

3. To fertilize your garden, use a half cup of liquid seaweed per 1000 square feet every month for eight months during the growing season. Skip during the 4 months of winter. Mix the liquid seaweed one third cup per gallon of water. This solution mixes well with liquid fish and molasses, or EM, compost tea and mycorrhizal fungi.

4. Seaweed has a neutral to slightly alkaline ph and can help neutralize acidic soil--a good thing for seaside gardens which are often acidic.

5. Kelp fertilizer is typically applied to the leaves in a diluted mixture by a hand sprayer. As the plant absorbs the sunlight, it will absorb the foliar application as well. While you can apply a kelp extract directly to the soil, foliar feeding directly to the leaves has proven to be twenty times more effective. Use 1/3 cup of liquid seaweed per gallon of water.

6. If your plants wilt or lose their color, adding the recommended amount of kelp extract will improve the health and appearance of the plants within the day. One spring a late frost hit my husband Lonnie's large garden and his young plants. Early in the morning before the sun was up he ran out to check his plants. They were all bowed over. He quickly took some seaweed extract solution and drenched each plant before the sun hit the garden. All his plants pulled out of the frosted wilt and survived.

7. Liquid seaweed can be used in hydroponic systems to preserve seedlings. Kelp extract ensures the water bed is fit for growth before it is able to host growth-necessary bacteria which takes 4-6 weeks to form.

8. My husband knows his plants are being fed enough when his plants are a dark blue green. He does not settle for the light green plants. He says his plants are hungry when they are just an average green. When he feeds properly with seaweed and fish emulsion fertilizer, his plants are a dark blue green.

For patio container gardening apply seaweed fertilizer weekly through the growing season.

For patio container gardening apply seaweed fertilizer weekly through the growing season.

Tips for Patio Container Gardening

Here are six tips for the best use of seaweed fertilizer for container gardening.

1. Use seaweed fertilizer combined with fish emulsion or a normal balanced fertilizer. Seaweed does not contain hefty amounts of sodium, phosphorus, or potassium. These minerals need to be supplemented. Seaweed is beneficial because of growth hormones, enzymes, and trace minerals not found in other fertilizers.

2. Apply the fertilizer weekly through the growing season. For herbs and perennials, apply bi-monthly. Feed your containers monthly or not at all in the winter. In the early spring and late autumn, feed half solution.

3. For granular fertilzer, usually a small handful suffices, sprinkled around the plant and forked in.

4. You can buy fortified seaweed where NPK is added. If using a feed of this type, you don't need to supplement.

5. For container gardening, you don't need to foliar spray or mist. Exception is in an emergency if a plant shows signs of nutrient deficiency.

6. Liquid seaweed is better for container gardening than kelp meal. Kelp meal needs to be broken down by soil microbes, which are much less in a container media.

One of the many brands available of seaweed and fish emulsion combination

One of the many brands available of seaweed and fish emulsion combination

Different Preparations of Seaweed Fertilizers

Seaweed can be used straight from the ocean and applied to your garden, or even DIY and prepare it as a storable fertilizer yourself. Instructions can be found on the internet. Getting seaweed directly from the ocean is not available to the majority of people, so I will not cover it here. Different preparations of seaweed are available in stores where most of us will be getting our seaweed fertilizers.

Kelp seaweed products come in several forms, including dried meal, powders, liquids and enzymatically digested formulas. These fertilizers are used primarily for the micronutrients and growth hormones they provide. Seaweed is a poor source of sodium, phosphorus and potassium. It may be combined with fish fertilizers,which boost the nitrogen. Fish formulas often have an objectionable smell, but the odor soon dissipates.

There is no danger in too much salt with seaweed fertilizing like there is with sea salt fertilizing. With sea salt fertilizing be sure and follow instructions.

While meal products are limited to soil applications due to insolubility, foliar feedings or root zone applications through drip lines are possible with liquid seaweed

Some forms of bottled liquid seaweed extract.

Some forms of bottled liquid seaweed extract.

Many Good Benefits to Seaweed Fertilizers

Seaweed fertilizers are a natural source of a broad range of nutrients that are good for plants and improving your garden soil. Plus most seaweed fertilizers are organic. Seaweed will make for strong, bountiful gardens. We had a friend who had two large pine trees that were dying from the base and working up. She told my husband about it and he recommended a seaweed fertilizer mix. Over a weeks time they put 2 gallons of seaweed and water mix over the root zone of each tree. Then they watched as the trees gradually came back to life and started growing again. I hope you, too, will experiment with many of these tips.

How to Foliar Spray with Seaweed and/or Fish Emulsion

Further Reading








Seaweed will make for a beautiful garden and an abundant harvest.

Seaweed will make for a beautiful garden and an abundant harvest.

Are you now interested in seaweed fertilizers?

© 2019 Doneta Wrate


Doneta Wrate (author) from Michigan on April 19, 2019:

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