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Oh Dear! Koh Samui Seaweed! :(

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So I took a quick trip down to Samui. All was good.

Had googled a bit about different types of fertilizer, and had read that seaweed and even seashells could make good fertilizer - great source of trace minerals, calcium, etc! While on the beach, saw loads of seaweed, and thought... hmm... perfect to put on my veggie plants. Let's gather some. Couldn't carry it on AirAsia, obviously, so I posted it back home. Box, arrived two days after I did.

Bit nuts, to post seaweed home... I know! But, thought I was going to have a bumper crop of toms. Perhaps I'd found the secret ingredient (then who would be laughing at my crazy idea, eh!):)

I unpacked all my sea goodies, stank to high-heaven.

Washed the salt off carefully, and proceeded to make seaweed tea, and crushed seashell tea.

I let things brew for a few days, then spread lovingly over my tomato plants.

Big mistake?


A couple of days later, the lower leaves on the tomatoes were starting to look funny. Kind of a dark tint to the leaf in places, but overwhlemingly a white/silver speckle to all of them. A week or more later, and the leaves are crispy. The upper, new leaves, look curled under. And all in all, my lovely tomato plants now look very poorly. (attached photos probably show it better)

So, what did I do something wrong? Is it a result of over fertilization, too much calcum? Or something completely different, like a virus or disease that I've given to the plants via the seaweed? Should I pull my tomato plants and start again from scratch!? Or is there a chance they will recover, or at least, still produce fruit?

If anyone has any ideas I'd love to hear.

(I'm not going to be gathereing seaweed from Samui again) LOL



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When you say "then spread lovingly over my tomato plants." do you mean that the brew actually came into contact with the leaves?

If applying a foliar spray it should be a very weak solution. Always better to apply to the soil.

You may not have got as much of the salt out as you think and this could have caused the damage.

Give the plants a bit more time and hopefully the new growth will look better.

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Seaweed extract, not seaweed and usually kelp not just weed. The "real" stuff isn't cheap so there must be more to the process. My guess is you managed to leech out all the salt plus pollutants into you tea. On tomatoes? Nar, don't think so. I'd be planting more seeds, not just in case. You could try drowning the soil around the plants as much as you to leech the salt out....

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Loong, no I put it on the soil, I generally don't foliar spray anything other than the 'pesticide' mix we discussed in another thread - soap, garlic, chilli, onion - when I have an issue with pests.

I think you might be right with the 'salt' idea.

I guess I just didn't wash it thoroughly enough...

I'm going to pull up the worst once, and planting new seeds, whilst trying to rescue some of the lesser damaged ones.

I'm really dissapointed, but I've learnt a great lesson!

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  • 3 weeks later...

Oh no wonder I can't find much sea weed around Samui, now!!! biggrin.png The Post man must have loved you! wink.png

I did a bit of an experiment with this last year, posted on Gardening on the islands thread... I just tried to make a direct link to the bit of discussion, but it won't allow me to do that!!!

But did not do on Toms, they just don't like the warmer nights here, so rarely see tomatoes grown successfully here~ !! sad.png

But basically I just put the "fresh" sea weed directly on the plants.... and no problems ! thumbsup.gif .... I wonder if the tea, mix built up too much salts? Some plants obviously are more "salt tolerant" than others...too...!

Hard to tell from OP images they are a little bit small...so as to see what's going on... If I remember from years back, salts turn the foliage brown and crispy.... looking.... ?

I have not seen locals using seashells, but they do use egg shells and charcoal.... but then too, my neighbours were skeptical about using sea weed!!! .... but the results were good for them too...

(crazy farang at it again! biggrin.png )

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When I did my pesticide permit long ago we were told that if we discovered belatedly that we had applied an overdose, we could solve the problem with activated charcoal. You have to be quick! I think this is sold as a constituent of water filters. Even if it is too late and you have salted the ground, this may be your only way out, along with watering a lot.. Or change it to a depth of ? 50cm? Good luck with that.

I was interested in your question and found:


Too much fertiliser = too much salt...

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i heard mixing into the soil, egg shells and hair are supposed to be good for toms but i can't say i've noticed a difference when i've tried it

Yes, I do this too. Hair/fur is pure nitrogen (my dog loves being brushed...LOL) and egg shells are calcium. I also add banana/potato peels when I have them, and epsom salts very occasionally.

Samuijimmy, I discovered (on another gardening forum) that my problem wasn't the seaweend (I thought it might have been because of the timing) but it was/is actually thrips and Spotted Wilt Virus. :(

I now have all my plants covered in tin foil mulch and netting, and oh my yes, another crazy farang at it again!!! :o Trying desperately to do whatever I can to repel the thrips. :)

The postman, I'm sure, wouldn't have thought I was nuts, as did everyone who saw me collecting the seaweed! LOL But I'm glad to see I'm not the only one! ;)

I didn't realise there was a gardening on the islands thread... I'll try and find it and take a look.

Edited by SundayAfternoon
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