‘Hello Garden Doctor,
I have heard that dried seaweed collected from the beach can be used as a beneficial addition to the garden. Just wondering if there are any other materials found at the beach or anywhere else that can be used as an organic garden addition?
Very thankful for any of your thoughts on this, Greg’
Natural organic fertiliser is the best way to feed your plants and improve your soil. The sea contains a large spectrum of trace elements in solution, and some of the debris that is washed up on the beach like seaweed, shells and rocks also contain quite a lot of these trace elements. After foraging at the beach on many an occasion I can tell you of quite a few materials that can easily be collected at the beach and recycled into the garden as organic fertiliser. The many types of shell, seaweed, sea sponge, cuttlefish and even pumice stones can all be used in varying ways that will benefit your garden.
Mulching with any of these materials will be beneficial. It will improve the soil, retain water and reduce the weeds. Seaweed is perhaps the best known of natural fertilisers from the sea, though shells have also been used in the garden for thousands of years. You can easily use crushed up seashells as a layer of mulch just like pebbles are used in some gardens. Be sure to thoroughly wash and then soak the shells in a bucket of water as seashells will be encrusted with salt. Pour off the water after two days and then soak the shells again to make sure excess salt has been leached out otherwise this could harm your garden. There is no need to break up small shells, so just collect those ones. You should really be able to find enough small shells pre-crushed by nature.
Collect all the crushed shells and apply a layer over the garden surface. To do this, simply throw or sprinkle the crushed shells out over the site you want to mulch, These shells will provide the soil the minerals and calcium as they decay, providing a good natural slow release fertiliser that is also organic. The great benefit is that the shells decay very slowly, preventing the need to replenish the mulch for at least a few years, and it is good for all types of plants such as flowers, trees, ground covers and many other herbs and vegetables. If at any time you need to compost around your plants, simply rake the seashells aside add compost, and then replace the shells back on top. You can use seashells as a surface mulch of your potted plants such as flowers or succulents, enhancing their appearance. You can also mix the sea shells into the soil and the coarseness will improve the drainage, which would be beneficial for any plant that likes a well-drained soil.
Using cuttlefish or even crushed lobster and crab shells can also be beneficial to the garden. Cuttlefish like all other shells is composed of calcium which is an important element in plant nutrition. After nitrogen, potassium and phosphorus, calcium, magnesium and to lesser extent iron are essential for plant growth. Cuttlefish bone is a pure form of calcium carbonate. Pulverised cuttlefish should be sprinkled around the garden, your pot plants and definitely in the compost. It is soft and easily broken into small pieces if wrapped in a cloth and hit with a hammer or large stone. It is a very useful way to provide a natural organic slow release of organic calcium. Crushed cuttlefish bone is an alkaline substance and is also very useful for neutralising soil acidity.
Pumice stones that can also be found washed up at the beach are also another useful addition to the garden. Pumice stones are very light, airy rocks that float on water. They originate from volcanic regions and contain many beneficial minerals for the garden. They can be broken up into chunks and added to the compost or around the garden as a slow release fertiliser. Pumice is soft and easily crushed. If the rocks are pulverized into dust then the mineral release will be much quicker. Pumice is beneficial for both clay and sand soils, helping to provide aeration in clay soils, and water retention for sandy soils.
Seaweed is the number one gift for your garden, as it contains an abundance of beneficial minerals and trace elements. It’s just too hard to walk by it at the beach and not pick it up. I prefer to take the dried seaweed, because that way you can fit more into your bag, and will be more concentrated in minerals by weight.
Crush it up in your hands or add it whole to your compost and garden beds, it is really one of the best things you can do for your garden. Seaweed is packed with everything that a plant and soil needs. The trace elements contained in the seaweed are transferred to the soil and then into the plant and its fruit. Seaweed is a good way of adding iodine to the soil. Iodine is a very important nutrient for human health, and these days many of the soils used for agriculture and the people eating the produce from them, are deficient. To make seaweed ‘tea’ fertiliser, soak seaweed in a container for a week or two until it begins to resemble the colour of tea. By this time it will contain all the trace elements and nutrients released from the seaweed. This would be far too strong to use on its own, so make sure to dilute a small cup with a full watering can and water it around the garden.
Seaweed itself contains little salt it is the sand attached to it that is quite alkaline and needs to be removed with a good wash. Seaweed can be used around almost any plant except acid loving plants such as strawberries. Sea sponge also contains many of the trace elements and minerals found in seaweed. When added to pot plants or sandy soils sea sponge will retain water (it is a sponge after all!), particularly useful for drought prone areas. Sea sponge is like a natural water crystal, absorbing and retaining moisture in the soil. Some people even use sea sponge as a medium in which to grow herbs without soil!
Put the seaweed, sea sponge, shells, cuttlefish and pumice in the compost as well as in the garden beds. With all of these items collected from the seashore be sure to thoroughly wash or soak them to remove excess salt which may leach out over a few days. All of these materials are a valuable, efficient natural source of fertiliser and mulch. The best bit is you can enjoy a walk along the beach whilst collecting it and it’s also free! With these additions your soil will be better off allowing you to save money and avoid using chemical fertilisers as soil additives or amendments.