Plant Doctor Archive

Using raw seaweed on the garden

I know a beach where there is a lot of washed-up plant material mixed with broken-down seaweed. It looks like a fine mulch and I used to get bags of it and spread it on the garden. Now I have been told that the sea salt in this mulch is bad for the soil and detrimental to plant growth. Is this true?

Yes, you could end up with a build-up of salts in your garden if you use this washed-up plant material. You may find sensitive plants fail to thrive.

If using seaweed for the garden as a mulch, soak it in fresh water overnight first to wash out the salt.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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