Seaweed and raised vegetable bed

butlerjonny · May 2020

Hi, complete beginner here! I am planning to install a 14” high raised bed over a patch that was previously part of a lawn. I have removed the grass / turf and dug over the patch to remove large stones and some tree roots, which I know is probably not strictly necessary since the raised bed is reasonably deep but I figured it probably wouldn’t do any harm. I’ll be filling the bed with a soil / compost mix. My question is this: I have collected a couple of bags of fresh seaweed from a local beach and I wondered if there is any benefit to laying this down over my patch before I put the raised bed on top? I’m thinking it might help kill off any remaining weeds etc that might be in the soil and also provide nutrients for some of the deeper rooted veg like carrots and parsnips? Or would I be better off to let it rot in the bags and use it later to add to the surface of the raised bed? I’d appreciate any advice. Thanks

fidgetbones · May 2020

It won't kill off weeds. I would give it a quick rinse in clear water then mix it in. Potatoes and beetroot love it.

Braidman · May 2020

Watched an old programme some time ago about western Ireland, some parts were just rocky outcrops, yet the people living there grew ample crops of potatoes and other vegetables without proper soil.

They collected sand and seaweed from the foreshore and grew every thing in it, no worries about it being salty or properly rotted!

The programme makers had a sample plot to show how it was done.

nick615 · May 2020

There's an added benefit to using it 'as is'. The salt content won't damage the soil to any great extent but will deter slugs who don't like salt at all.

butlerjonny · May 2020

Thanks very much for the input. Good to know the slugs are deterred by the salt.

So I think I’ll just mix the seaweed that I have now in to the raised bed as I fill it with soil and compost, and then get some more fresh stuff to use as a mulch whenever I plant out my seedlings in a couple of weeks time.

Really interesting about the West of Ireland spuds. I remember reading about that before, how families had actually “built” a field of fertile soil over several
generations using seaweed and sand, and many managed to survive the Great Famine because of it.

Thanks again

Braidman · May 2020

I believe it was the variety of potato that they all grew was the problem, up to then they did not appear to have a problem, then when the blight struck every plant was affected.

Me, I had to stop growing Desiere and Maris Piper on my plot as I was always getting rotten potatoes due to blight, very seldom are other varietie affected!

The two old chaps on either side of my plot grow desiere and never have a problem with blight!

nick615 · May 2020

I'm told that, here in W Cork 50 years ago, locals would regularly go down to the coast and bring back 'green sand' by horse and cart. Exactly what that was, I've never investigated but it may have involved seaweed in some way. Spuds like Desiree are treated with total contempt as being 'like a bar of soap' - great for we 'blowins' but not floury enough for locals.

jassybarnewell · March 2021

Thanks for tip about seaweed. I live in Greystones. Co Wicklow and right by the sea. That’s a great help

Fire · March 2021

I would personally rinse it.

Skandi · March 2021

@nick615 They might actually mean greensand which is a type of rock deposit. it's very high in minerals so if you have it in your area that is probably what they were collecting.

Allotment Boy · March 2021

My father used seaweed, when stationed in Oban during WW2. He said he grew the best cabbage & potatoes he ever had.

Seaweed and raised vegetable bed

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