Using Seaweed in the Garden

Early Winter is a great time to put fresh seaweed on your empty beds. I just gather the wet seaweed that washes up on the beach (not the stuff still growing attached to rocks) and lay it out on the beds and let the rain wash it clean. By Spring it will have decomposed into the bed. It can get a bit glutinous and unappealing during this process but unless you are hoping to have quality time hanging out beside it, it's nothing that will bother you. You could also cover with soil.

The above photo is a bag of seaweed I collected on my local beach last week. I tried to avoid the large stems that are often attached as they are slower to break down, although as I am typing I am recalling someone telling me that the stem is the most nutritious part.... not sure if that is a real memory. Seaweed definitely improves the soil. My main vegetable patch in my old house produced its best crops in the season directly after my first application of seaweed. The effect was unmistakable.

And thanks to my penchant for taking photos of the garden constantly, I have before and after photos. The first photo was taken in November and the second photo was taken in the following July:

Not only does applying seaweed cover the bare soil reducing leaching of existing organic matter, it keeps the soil moist and adds nutrients including nitrogen, potassium, phosphate and magnesium. It also contains elements that plants need in small amounts like iron, manganese, copper, boron and zinc, which can be lacking in other fertilisers. It doesn't contain any weed seeds either. You can safely apply fresh seaweed directly as a mulch to your growing crops as well as digging it in to the soil. Opinions vary as to whether you should rinse it first or not. Some people think the salt will deter slugs, others say it might damage certain plants.


This is my new garden where I am just beginning my vegetable patch. I made a few beds last year which produced some beautiful vegetables but I've decided that they are too close to the septic tank for comfort. I'm worried about contamination in the soil from the soakaway. The following photo is the other side of the garden. All I've done here so far is cover three areas with large pieces of carpet to kill off the undergrowth. The carpet has been down two months. One bed has been covered with seaweed this week, and two more to go. For the other two beds I am going to shovel a load of compost from my garden heap on to the bare soil and then cover with seaweed. I am significantly excited writing this. Better get my wellies out tomorrow.