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potted tomato mulched with seaweedSea­weed is the sea’s gift to our edible garden. After a big storm the beaches are laden with detrit­us — a won­der­ful mix of sea­weed, sand, sticks and the odd sand hop­per. A stroll by the sea on a blustery day col­lect­ing sea­weed in a sack might be just the ton­ic you and your garden need.

Sea­weed is a rich source of a wide range of micronu­tri­ents. Think of it as a mul­tiv­it­am­in in your soil’s diet. Many of the nutri­ents are needed by our plants in only minute quant­it­ies but without them they will fail to thrive. If those trace ele­ments aren’t in our veget­ables, they are not in our diets, so we’ll suf­fer too. Sea­weed also con­tains plenty of organ­ic mat­ter, it’s seed-free and as it meshes togeth­er it doesn’t blow around. It rots down fairly slowly, par­tic­u­larly if it dries out, so releases its magic in a gradu­al, sus­tained way.

Choose dry sea­weed, if you get a choice, because it’s light­er and easi­er to carry. I’ve nev­er chopped, washed or sor­ted it, just taken the sandy, salty offer­ings and tossed out any plastic and stones. There are some areas where you aren’t allowed to col­lect sea­weed, includ­ing mar­ine reserves. Apart from these, choose some­where with easy access that will have had onshore winds the night before to heap up rich pick­ings. I pri­or­it­ise my use of sea­weed in five ways:


  1. Potato mulch
Sea­weed mulch keeps pota­toes moist, pro­tects the first shoots from the wind, pre­vents green pota­toes and provides a con­tinu­ous liquid feed. I spread the first lay­er in ‘nests’ around the emer­ging shoots, then add anoth­er lay­er about a month later. The weeds are sup­pressed and the sea­weed doesn’t blow away like some oth­er mulches. When you dig up your pota­toes they come out clean, the soil is full of worms and the pro­cess of dig­ging incor­por­ates the remain­ing sea­weed into the soil to feed your next crop.
  2. Liquid feed
You can make your own liquid fer­til­iser by soak­ing any­thing from fish scraps to horse manure in a bar­rel of rain­wa­ter and using the res­ult­ing liquid or ‘tea’. A litre of sea­weed tea scooped into a 10-litre water­ing can and topped up with water will give an invig­or­at­ing weekly feed for any­thing from seed­lings to strawberries.
  3. Foli­ar feed
Plants absorb nutri­ents through their leaves as well as their roots. Mist­ing with sea­weed tea will both feed them and also seems to increase their res­ist­ance to fungal infec­tions such as blight and mildew.
  4. Slug and snail deterrent
Unwashed sea­weed has proven to be one of the most effect­ive deterrents against slugs and snails that I’ve deployed in my garden. Vul­ner­able seed­lings such as beans, lettuces and corn have sur­vived unscathed when planted into a ring of sea­weed. While a little labor­i­ous to achieve, it’s a worth­while defence if you choose not to use slug pellets.
  5. Com­post
If you’ve got more sea­weed than you can use dir­ectly in your garden, you can add it to your com­post heap. It will com­post best when mixed with oth­er ingredi­ents. I empty the sea­weed tea bar­rel on to the com­post heap at the end of the grow­ing sea­son to make the most of the remain­ing sludge.

There is no such thing as a free feed, but col­lect­ing and using sea­weed tossed up on the sand is about as close as you can get. You get to enjoy the bene­fit of spend­ing time on the beach and your garden gets to bene­fit from the sea’s rich harvest.


potatoes mulched with seaweed (2)

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