Seaweed fertilizer: how to maximise this marine magic

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Using seaweed fertilizer for crops and gardens is a centuries-old process. In Scotland it’s known as feannagan and in the Channel Islands as vraicking.

What’s so great about seaweed?

It contains minerals and vitamins such as nitrogen, potassium, phosphate and magnesium which give plants a real boost.

What do these minerals and vitamins actually do?

They stimulate microbes leading to healthier soils and better roots. Fertilizing little and often helps maintain high chlorophyll levels and bolsters a plant’s defences against pests and diseases.

Seaweed fertilizer also helps guard against frost damage and transplant shock.

Which plants can I use it for?

From seeds to lawns, young plants to mature trees, seaweed fertilizer is a universal tonic. It can be used on any plant all year round.

Can I collect my own seaweed?

Coastal gardeners have been collecting this bounty of the sea for centuries. However in the UK there is no public right to collect seaweed unless you own the beach. There are bans in place if it’s a Site of Special Scientific Interest or a special area of conservation. It’s probably best to check with the local council and land owner first.

To make sure it remains sustainable never rip seaweed from the rocks. Just collect strands that have washed up. They can be heavier than you think! Then leave the seaweed out in the rain for a few months to wash away the salt before using on your garden.

Alys Fowler has more information on harvesting in her Want to boost your soil? Get seaweed article.

How much seaweed fertilizer will I need?

  • Feeding to the roots: 40 – 50 ml per gallon of water
  • Spraying on leaves: 10 – 20 ml per gallon of water

What seaweed fertilizer products are available?

We stock Maxicrop, sold in 40 countries for more than 50 years. Soil-Association approved, the range includes:

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