Seaweed Powder & Extract | 100% Soluble Kelp

Organic seaweed powder — 100% soluble Ascophyllum nodosum with tested growth hormones

Seaweed is not a fertiliser in the conventional sense. It supplies very little nitrogen, phosphorus, or potassium. What it delivers — and what no synthetic fertiliser can replicate — is a concentrated package of natural plant growth hormones, complex polysaccharides, and bioactive compounds that prime the plant's own growth and defence systems. This is the difference between feeding a plant and activating it.

This powder is pure Ascophyllum nodosum — the most extensively researched seaweed species in agriculture, with over 70 years of published science behind it. It is not a liquid extract diluted with water and preservatives. It is the whole seaweed, dried and milled to an ultra-fine, fully water-soluble powder that dissolves instantly with no sediment, no clogging, and no residue. Every gram contains the full spectrum of bioactive compounds in their natural ratios: cytokinins, auxins, alginic acid, laminarin, mannitol, fucoidans, betaines, amino acids, and over 60 trace elements.

The growth hormones in this product are laboratory tested — cytokinins verified at <200 ppm and gibberellins at <100 ppm. Most liquid seaweed products on the market do not test or declare hormone content, meaning you cannot know what you are actually applying. This powder delivers consistent, verified biostimulant activity with every application.

What seaweed powder is used for in the garden

• Root development and transplant establishment — cytokinins and auxins stimulate rapid root cell division; applying seaweed at transplanting accelerates root recovery and establishment
• Stress resistance and recovery — betaines, mannitol, and proline act as osmoprotectants that stabilise cell membranes under drought, frost, heat, and salinity stress
• Yield and fruit quality improvement — peer-reviewed meta-analyses report an average 15% yield increase across crops, with improvements in sugar content, vitamin C, and flavour
• Soil biology activation — alginic acid and polysaccharides feed beneficial soil microorganisms, increasing rhizosphere diversity and nutrient cycling
• Seed treatment and germination — soaking seeds in dilute seaweed solution improves germination rates and produces seedlings with stronger root systems
• Foliar nutrient uptake enhancement — alginic acid acts as a natural wetting agent and chelator, improving absorption of any co-applied foliar nutrients
• Disease suppression — triggers systemic acquired resistance (SAR), upregulating defence genes against fungal and bacterial pathogens
• Flower set and fruit retention — cytokinin activity delays senescence in flowers and developing fruitlets, improving fruit set rates

Why powder rather than liquid seaweed?

The science of seaweed biostimulation: how Ascophyllum nodosum activates plant growth and defence

Why Ascophyllum nodosum is not an ordinary seaweed

Of the thousands of seaweed species in the world's oceans, Ascophyllum nodosum — the knotted wrack of the cold North Atlantic — is the single most studied species in agricultural science. It grows in the intertidal zone, exposed twice daily to extreme environmental swings: desiccation, UV radiation, freezing, osmotic shock, and mechanical wave stress. To survive this, it has evolved an extraordinarily complex biochemistry rich in protective compounds that happen to be directly useful to land plants when applied as a biostimulant.

Published analyses of dried Ascophyllum nodosum report approximately 28% alginic acid, 11.6% fucoidans, 7.5% mannitol, and 4.5% laminarin as the dominant carbohydrate fractions. The protein content is approximately 5%, and the phenolic content approximately 1.4%. It also contains a full suite of phytohormones — cytokinins (primarily trans-zeatin), auxins, gibberellins, and abscisic acid — in concentrations sufficient to trigger measurable hormonal responses in treated plants.

Six mechanisms of action

How to use seaweed powder: preparation, application rates & guide

Application rates

Step-by-step preparation

1. Measure the powder. 1g is approximately half a level teaspoon. For a standard 10-litre watering can, measure 7–8g.
2. Add powder to water and stir. Sprinkle onto the water surface and stir briefly. Dissolves within seconds — no clumps, no straining.
3. Apply immediately or within 24 hours. Root drenches around the base; foliar sprays targeting both leaf surfaces.
4. Combine with other feeds if desired. Fully compatible with all Dr Forest fertilisers. Alginic acid improves uptake of co-applied nutrients.
5. Store dry powder sealed in a cool, dry place. Shelf life of several years. Avoid moisture ingress.

Frequently asked questions about seaweed powder