Making the most of our free fertiliser

By Richard Wright

Published on Friday, December 07, 2012 - 13:32


Making the most of our free fertiliser

The tide is in but there is plenty of seaweed on the slipway.

GARDENING I MAKE no apology for returning to a perennial gardening theme on this Island of ours which is surrounded by the sea and, more importantly, seaweed.

I regularly promote collection and use of the stuff, which is free and all around us — although it has been pointed out to me that not everyone has the time, energy or indeed a car with a trailer to collect the magical stuff.

At the weekend, predictably, I did not check the tide table and trolled down to my favourite collection spot — only to discover the tide was completely in.

But a useful tip for fellow foragers is the public slip, off St Thomas’s Street in Ryde, is a great catch-point for the stuff, especially after a good blow of wind and heavy seas.

It was tips from a couple of readers which led me in the direction of making a perhaps more practical liquid feed, which also acts as an insect deterrent.

One correspondent led me to the excellent Ventnor Permaculture website (www.ventnorpermaculture., while another said seaweed extract made not only an excellent foliar feed but it sent the whitefly infestation on her tomato plants packing.

Whitefly can be a difficult pest to deter when they reach plague proportions because gardeners, quite rightly, have an in-built aversion to using anything noxious near fruit they are going to eat.

In the past, I’ve used a home-made mix of un-perfumed soap, steering clear of dishwashing liquid, which these days always seems to have more smell than bubbles, and vegetable cooking oil.

One quarter of a bar of soap can be soaked in water for long enough to make it soluble and then combined with one tablespoonful of vegetable cooking oil. Then, mix it into a half gallon of water.

If that water already has a one eighth part of seaweed liquor then you have a double bug deterrent and foliar feed at the same time.

But, how to make the seaweed stuff from a raw material which is rich in trace elements and potassium?

It couldn’t be much easier, and your plants will say a huge thank you for the elixir of life, which will contain scores of different nutrients from which they can benefit.

Part of how to do it came from Ventnor Permaculture a couple of years ago but it is not rocket science.

Fresh and clean seaweed after a storm is the best and it is recommended, although not essential, to give it a good wash before popping it in a bucket. That reduces the salt content of the final mix.

Any size of container will do, depending on how much you want, but the proportions remain the same whatever the size.

Half fill with weed and top up with water and let it stand for three months, giving the potion a stir every now and again.

The longer you leave it up to that three-month ceiling the more you will get out of it. By the time it stops smelling of ammonia, the process is probably complete and a lid helps if it is to be sited close to the house and to prevent evaporation.

At the end of the process, take out the remaining solids, add them to the compost and strain off the remaining liquid.

A household sieve will take out the bigger bits and the remaining solids in suspension will settle, which can be seen if the liquor is stored in old, clear fizzy pop bottles.

It can then be poured off for dilution of about a cup to each gallon of water, although that is not an exact science because there are too many variables. As I have often said before, in its raw state seaweed is especially valuable as mulch around trees, shrubs and roses, where a 6ins layer kills competitor weeds and adds nutrients to the roots.

Added to your compost heap, it adds both goodness and organic structure. Spread direct on the vegetable plot prior to digging, it holds back weeds before being dug in later, when soil conditions allow.

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