10 Best Liquid Seaweed Fertilizer of 2025

Tested and Reviewed: Top 10 Liquid Seaweed Fertilizer deals with expert ratings from 8.1 to a perfect 10

March 2026 Edition

Editor's Choice

9.7

GS Plant Foods

GS Plant Foods Liquid Kelp Fertilizer – Suitable for Organic Growing, OMRI Listed Seaweed Concentrate for Lawns, Gardens & Soil - 1 Gallon (Makes Up To 800+ Gallons)

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Editor's bottom line:

“This liquid seaweed fertilizer is the best one we tested. In terms of quality, brand and price, we couldn't ask for more.”

Main Highlights

Organic Materials Review Institute Listed for Organic Use- Certified for use in organic gardening and farming, this natural seaweed extract fertilizer made from Ascophyllum Nodosum provides a balanced source of trace minerals and organic compounds that nourish plants and soil.
Supports Soil Health & Nutrient Availability- Helps maintain favorable soil conditions and assists in nutrient uptake from the soil, contributing to healthy, productive plants.
Suitable for All Types of Plants- Safe and effective for vegetables, fruits, ornamentals, lawns, trees, and shrubsused by home gardeners and commercial growers as part of a regular fertility program.
Simple, Flexible Application- Mix 2 ounces of concentrate per gallon of water and apply to soil or foliage with a sprayer, watering can, or hose-end sprayer. One gallon of solution treats up to 1,000 sq. ft.
Trusted Quality from GS Plant Foods- We take pride in producing sustainable, high-quality organic fertilizers that are easy to use and compatible with any growing system. Consistent performance backed by a satisfaction commitment.

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9.5

Blue Planet Nutrients

Liquid Kelp Seaweed Fertilizer Concentrate - Blue Planet Nutrients Ascophyllum Nodosum Liquid Seaweed Supplement - Makes 470 Gallons - Quart (32 oz)

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Main Highlights

Explosive Root & Plant Vitality: Premium liquid kelp concentrate derived from Ascophyllum nodosum seaweed delivers natural growth hormones, trace minerals, and amino acids for stronger roots and lush foliage in every garden.
Makes Up to 470 Gallons from One Quart: Super-concentrated liquid seaweed fertilizer use just ½2 tsp per gallon (2.510 ml) in soil, hydroponic, coco coir, or aeroponic systems and turn one quart into up to 470 gallons of ready-to-use plant food.
Stress & Drought Defense: Seaweed extract boosts natural resistance to heat, cold, transplant shock, and drought while improving nutrient uptake perfect for vegetables, flowers, herbs, fruit trees, and houseplants.
Safe From Seedling to Harvest & Every Application Method: Use as root drench, foliar spray, reservoir additive, or transplant soak 100 % soluble, non-clogging, and gentle enough for clones and seedlings yet powerful through flowering and fruiting.
Trusted by Thousands of Growers: 4.7 Stars from 3,570+ Verified Reviews Made from Organic Ascophyllum Nodosum Seaweed, Vegan, and Proven in Hydro, Soil, and Outdoor Gardens Nationwide.

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9.5

Bloom City

Bloom City Organic Liquid Seaweed and Kelp Fertilizer Supplement, Quart (32 oz) Concentrated Makes 180 Gallons

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Main Highlights

FULLY ORGANIC SEAWEED AND KELP: A seven species blend of Ascophyllum Nodosum, Palmaria Palmata, Ecklonia Maxima, Laminaria Saccharina, Chlorella Vulgaris, Arthrospira Platensis, and Chondrus Crispus.
EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelps unique processing techniques give the cleanest possible kelp extract. Get all the benefits of natural kelp enzymes and hormones without the non-nutritious fibrous pulp that gives other kelps their thick, brackish appearance. You can see the difference.
SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, its that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
FORMULATED AND MADE IN THE USA: Designed by botanists and plant chemists. Bloom City chooses only the highest quality ingredient sources and manufacturing methods to create the worlds best craft growing nutrient systems

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9.2

FoxFarm

FoxFarm Bushdoctor Kelp Me Kelp You Fertilizer, Liquid Seaweed Extract for Plants, Vegetables, & Flowers - Promotes Root Growth & Soil Health - Perfect for Hydroponics & Soil, NPK 0.5-0-0.5 (Quart)

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Main Highlights

SUPERFOOD FOR ALL YOUR PLANTS: Fox Farm seaweed fertilizer for plants is a natural liquid seaweed extract designed to nourish plants, including fruits, vegetables, & flowers. It enhances growth & vitality, as it is perfect for both soil & hydroponic
PURE NORWEGIAN KELP POWER: Made from Ascophyllum nodosum, this organic liquid kelp fertilizer for plants is packed with natural growth-promoting substances. These substances improve soil structure, & enhance root growth, ensuring your garden thrives
GARDEN GREEN WITH CONFIDENCE: Enjoy worry-free gardening with our seaweed plant food, as it is safe for children, pets, & the environment. Supporting sustainable gardening practices without compromising safety, its the eco-friendly choice you can trust
VITAL SUPPLEMENT FOR LUSH GROWTH: This seaweed extract fertilizer is an excellent supplement, not a primary plant nutrient, that enhances your fertilizer routine. It's a valuable addition to your gardening supplies, promoting vigorous & higher yields
EASY TO APPLY FOR ALL SETTING: The use of kelp liquid fertilizer is a breeze, whether you prefer foliar spraying or soil application. Simply mix with water and apply 2-3 times in early spring, then twice after the fruit set for best results

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9.0

Bloom City

Bloom City Organic Liquid Seaweed and Kelp Fertilizer Supplement (128 oz) Concentrated Makes 750 Gallons

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Main Highlights

FULLY ORGANIC SEAWEED AND KELP: A seven species blend of Ascophyllum Nodosum, Palmaria Palmata, Ecklonia Maxima, Laminaria Saccharina, Chlorella Vulgaris, Arthrospira Platensis, and Chondrus Crispus.
EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelps unique processing techniques give the cleanest possible kelp extract. Get all the benefits of natural kelp enzymes and hormones without the non-nutritious fibrous pulp that gives other kelps their thick, brackish appearance. You can see the difference.
SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, its that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
FORMULATED AND MADE IN THE USA: Designed by botanists and plant chemists. Bloom City chooses only the highest quality ingredient sources and manufacturing methods to create the worlds best craft growing nutrient systems

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8.8

Bloom City

Organic Liquid Seaweed and Kelp Fertilizer Supplement by Bloom City, (8 oz) Concentrated Makes 45 Gallons

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Main Highlights

FULLY ORGANIC SEAWEED AND KELP: A seven species blend of Ascophyllum Nodosum, Palmaria Palmata, Ecklonia Maxima, Laminaria Saccharina, Chlorella Vulgaris, Arthrospira Platensis, and Chondrus Crispus.
EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelps unique processing techniques give the cleanest possible kelp extract. Get all the benefits of natural kelp enzymes and hormones without the non-nutritious fibrous pulp that gives other kelps their thick, brackish appearance. You can see the difference.
SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, its that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
FORMULATED AND MADE IN THE USA: Designed by botanists and plant chemists. Bloom City chooses only the highest quality ingredient sources and manufacturing methods to create the worlds best craft growing nutrient systems

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8.6

TPS NUTRIENTS

TPS NUTRIENTS Seaweed Fertilizer for Plants, Premium Organic Liquid Kelp for Gardening, Concentrated Liquid Plant Food 8 oz (250mL)

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Main Highlights

Made with Seaweed-Based Nutrition Formulated to support healthy growth using seaweed-derived plant nutrients.
Supports Root Development & Plant Strength Helps encourage stronger roots and balanced plant growth.
Promotes Overall Plant Vitality Supports foliage health and steady development across plant types.
Ideal for Indoor & Outdoor Use Suitable for houseplants, gardens, containers, and outdoor plantings.
Made in USA

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8.3

Blue Planet Nutrients

Liquid Kelp Seaweed Fertilizer Concentrate (Gallon) - Blue Planet Nutrients Ascophyllum Nodosum Liquid Seaweed Supplement - Makes 1,600+ Gallons - Organic Kelp for All Plants & Gardens

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Main Highlights

Explosive Root & Plant Vitality: Premium liquid kelp concentrate derived from Ascophyllum nodosum seaweed delivers natural growth hormones, trace minerals, and amino acids for stronger roots and lush foliage in every garden.
Makes 1,600+ Gallons from One Gallon Jug: Super-concentrated liquid seaweed fertilizer use just ½2 teaspoons per gallon (2.510 milliliters) in soil, hydroponic, coco coir, or aeroponic systems and turn one gallon into over 1,600 gallons of ready-to-use plant food.
Stress & Drought Defense: Seaweed extract boosts natural resistance to heat, cold, transplant shock, and drought while improving nutrient uptake perfect for vegetables, flowers, herbs, fruit trees, and houseplants.
Safe From Seedling to Harvest & Every Application Method: Use as root drench, foliar spray, reservoir additive, or transplant soak 100 % soluble, non-clogging, pH-neutral, and gentle enough for clones and seedlings yet powerful through flowering and fruiting.
Trusted by Thousands of Growers: 4.7 Stars from 3,570+ Verified Reviews Made from Organic Ascophyllum Nodosum Seaweed, Vegan, and Proven in Hydro, Soil, and Outdoor Gardens Nationwide.

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8.1

Maxicrop

Maxicrop Liquid Seaweed (Kelp Extract, 32 Oz

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Main Highlights

Pure seaweed extracts initiate cell growth and vigorous root and stem growth
Trace elements that Maxi crop Liquid Seaweed contains are important as activators of enzyme systems
Maxi Crop's basic is a pure 100% seaweed extract

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8.1

Neptune's Harvest

Neptune's Harvest Fish & Seaweed Liquid Fertilizer (2-3-1) - 18oz Pint - Plant Food for Garden - Indoor & Outdoor Organic Plant Fertilizer for Vegetables, Flowers, Fruit, Trees & Lawns

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Main Highlights

Combined for Maximum Growth: Neptunes Harvest Fish & Seaweed organic fertilizer is an organic all-purpose liquid plant food formulated with 75% fish and 25% seaweed for a perfect blend of nutrients; this organic plant fertilizer delivers consistent feeding as a liquid fertilizer and plant food for vegetables, flowers, trees, lawns, and indoor plants, supporting balanced growth throughout the growing season and is safe for kids and pets
Power of Fish & Seaweed: This fish & seaweed organic plant fertilizer uses hydrolyzed fish and seaweed to supply essential nutrients in a balanced, plant-ready form; the organic all-purpose liquid fertilizer improves flavor and nutritional value of produce, brings out bright color in flowers, and supports strong plant development, making it a reliable liquid fertilizer for gardens, lawns, and indoor plants
How to Use: This organic all-purpose liquid plant food is easy to use and highly efficient, requiring only 1 oz. per gallon of water; the liquid fertilizer can be applied as a soil drench or foliar feed and is excellent for transplants and established plants; for indoor plants, mix 1 tablespoon per gallon of water and feed weekly; for outdoor plants, mix 1/8 cup per gallon of water and apply every 1-2 weeks; this organic liquid fertilizer fits seamlessly into multiple gardening routines
Supports Soil Performance: This fish & seaweed fertilizer builds organic matter, feeds beneficial bacteria and microbes, and improves soil structure over time; soil becomes looser, retains moisture, drains better, and supports healthier roots; this organic fish fertilizer is OMRI Listed, sequesters carbon, and helps plants become less susceptible to insects and disease while improving long-term soil quality
Package Contents: Neptune's Harvest Fish & Seaweed Liquid Fertilizer (2-3-1) - 18oz Pint (Pack of 1)

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Our Best Overall Choice

Best Choice

9.7

GS Plant Foods

GS Plant Foods Liquid Kelp Fertilizer – Suitable for Organic Growing, OMRI Listed Seaweed Concentrate for Lawns, Gardens & Soil - 1 Gallon (Makes Up To 800+ Gallons)

Free Shipping

Editor's bottom line:

“This is the best one we tested. In terms of quality, brand and price, we couldn't ask for more.”

Main Highlights

Organic Materials Review Institute Listed for Organic Use- Certified for use in organic gardening and farming, this natural seaweed extract fertilizer made from Ascophyllum Nodosum provides a balanced source of trace minerals and organic compounds that nourish plants and soil.
Supports Soil Health & Nutrient Availability- Helps maintain favorable soil conditions and assists in nutrient uptake from the soil, contributing to healthy, productive plants.
Suitable for All Types of Plants- Safe and effective for vegetables, fruits, ornamentals, lawns, trees, and shrubsused by home gardeners and commercial growers as part of a regular fertility program.
Simple, Flexible Application- Mix 2 ounces of concentrate per gallon of water and apply to soil or foliage with a sprayer, watering can, or hose-end sprayer. One gallon of solution treats up to 1,000 sq. ft.
Trusted Quality from GS Plant Foods- We take pride in producing sustainable, high-quality organic fertilizers that are easy to use and compatible with any growing system. Consistent performance backed by a satisfaction commitment.

Show Price

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