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Best seaweed fertilizers - May 2026

Last Updated - May 26, 2026

1
Best Choice

✖
Our rankings are cleverly generated from the algorithmic analysis of thousands of customer reviews about products, brands, merchant’s customer service level, popularity, trends and more. The rankings reflect our opinion and should be a good starting point for shopping.

Bloom City

Bloom City Seaweed and Kelp Fertilizer – Liquid Seaweed Supplement for Stronger Roots, Faster Growth & Improved Stress Tolerance, 1 Gallon

Bloom City

$39.99

More Details
Main highlights
- SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, it’s that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
- 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.
- 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 world’s best craft growing nutrient systems
- FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
- EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelp’s 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.
$39.99
2

✖
Our rankings are cleverly generated from the algorithmic analysis of thousands of customer reviews about products, brands, merchant’s customer service level, popularity, trends and more. The rankings reflect our opinion and should be a good starting point for shopping.

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)

GS Plant Foods

$39.95

More Details
Main highlights
- Promotes Green, Resilient, Thriving Plants – Supports plant vitality under stress conditions like heat, drought, and poor soil quality.
- OMRI Listed & Suitable for Organic Growing – GS Plant Foods kelp fertilizer meets the National Organic Program requirements for use in organic production. Ideal for gardeners, farmers, and home growers.
- Natural Seaweed Extract from Ascophyllum Nodosum – Sourced from one of the most nutrient-rich marine plants, this kelp fertilizer enhances chlorophyll production, root development, and nutrient uptake.
- Feeds from the Roots Up – Encourages strong root systems and improves overall soil health, leading to stronger, more resilient plants.
- Boosts Flowering & Growth – Helps improve plant productivity and bloom quality in vegetables, flowers, lawns, and shrubs.
$39.95
3

✖
Our rankings are cleverly generated from the algorithmic analysis of thousands of customer reviews about products, brands, merchant’s customer service level, popularity, trends and more. The rankings reflect our opinion and should be a good starting point for shopping.

Bloom City

Bloom City Seaweed and Kelp Fertilizer – Liquid Seaweed Supplement for Stronger Roots, Faster Growth & Improved Stress Tolerance, 32 oz

Bloom City

$19.99

More Details
Main highlights
- SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, it’s that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
- 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.
- 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 world’s best craft growing nutrient systems
- FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
- EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelp’s 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.
$19.99
4

✖
Our rankings are cleverly generated from the algorithmic analysis of thousands of customer reviews about products, brands, merchant’s customer service level, popularity, trends and more. The rankings reflect our opinion and should be a good starting point for shopping.

Blue Planet Nutrients

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

Blue Planet Nutrients

$19.95

More Details
Main highlights
- 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.
- 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.
- Makes Up to 470 Gallons from One Quart: Super-concentrated liquid seaweed fertilizer — use just ½–2 tsp per gallon (2.5–10 ml) in soil, hydroponic, coco coir, or aeroponic systems and turn one quart into up to 470 gallons of ready-to-use plant food.
- 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.
$19.95
5
Best Value

✖
Our rankings are cleverly generated from the algorithmic analysis of thousands of customer reviews about products, brands, merchant’s customer service level, popularity, trends and more. The rankings reflect our opinion and should be a good starting point for shopping.

Blue Planet Nutrients

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

Blue Planet Nutrients

$18.95

$19.95
(5% Off)

More Details
Main highlights
- 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.
- 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.
- Makes Up to 470 Gallons from One Quart: Super-concentrated liquid seaweed fertilizer — use just ½–2 tsp per gallon (2.5–10 ml) in soil, hydroponic, coco coir, or aeroponic systems and turn one quart into up to 470 gallons of ready-to-use plant food.
- 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.
$18.95
$19.95 (5% Off)

Best seaweed fertilizers - May 2026

Bloom City Seaweed and Kelp Fertilizer – Liquid Seaweed Supplement for Stronger Roots, Faster Growth & Improved Stress Tolerance, 1 Gallon

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)

Bloom City Seaweed and Kelp Fertilizer – Liquid Seaweed Supplement for Stronger Roots, Faster Growth & Improved Stress Tolerance, 32 oz

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

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

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