Seaweed products – perfect for your garden

Gardeners have always been aware of just how good seaweed and seaweed products are for the garden – used much like any other plant tonic and an organic alternative to synthetic fertilisers

You don’t have to live by the seashore to have the benefits of seaweed in your garden. There are many dried and liquid forms available of this traditional fertiliser.

Seaweed has been used as a soil improver and plant feed for centuries, and of course was most used in coastal areas, where it could be just picked up from the beach. There are old photographs of the beach near the gardens of Heligan, with horse-driven carts being loaded up with seaweed to take back up to the gardens. But there is no public right to do this. If you plan to gather seaweed in this way, check first with the local council or the landowner, if known. Some beaches are designated as sites of special scientific interest or as a special area of conservation.

If you have access to fresh seaweed, it is a useful substitute for farmyard manure, and does not need to be rotted down  before use. It’s best dug in fresh before it has time to dry, to one or two spades’ depth beneath the surface. There is not enough salt in seaweed to damage crops or soil, and any salt will leach out with rainfall or watering as it is highly soluble. You can add it to the compost heap, mixing it with woody or fibrous material such as prunings or paper so that it does not become slimy as it would with only a mix of vegetable scraps or lawn clippings. It could be used as a mulch, but as it smells and tends to be slimy, it’s probably better to dig it in.

It contains several useful plant nutrients including nitrogen, potassium, phosphate and magnesium. It’s also a common additive to fertilisers, both organic and nonorganic types. It contains the trace elements often lacking in commonly used fertilisers such as blood, fish and bone or other commercial brands.

If you garden organically and want to avoid using synthetic fertilisers, then seaweed-based products could be your choice. Seaweed and seaweed fertilisers are usually a sustainable and renewable source of nutrients.

There is a selection of seaweed products to choose from these days. Some can be applied as foliar feeds, when the nutrients are sprayed on to the foliage of a plant and taken up through the leaves.

Fresh seaweed and products made from it are not considered to be true fertilisers as their plant nutrient content is not guaranteed or standardised. But there are a number of garden fertiliser products that contain additional seaweed extracts.

Dried seaweed products include seaweed meal from crushed and dried seaweed, powdered seaweed extract produced by boiling and evaporating off the liquid to leave a concentrated solid extract that is made into powder, and liquid seaweed extract made from fresh seaweed through water extraction.

There are fortified seaweed products, usually available in liquid form that contain additional nitrogen, phosphorous and potassium. Calcified seaweed is made from naturally occurring beds of calcified and coralline algae. Some sources are more sustainable and renewable than others, so you may like to get more information from the manufacturer. Used in the garden it is an alternative to garden lime (although more expensive), with added trace elements and plant nutrients. Always read the label for instructions.

Seaweed facts

• Seaweed products can be used much like any kind of plant tonic
• Organic alternative to synthetic fertilisers
• Dug in fresh, it is like any other soil conditioner
• Fresh seaweed does not have to be rotted down like horse manure
• Can be put on the compost heap with added paper and prunings
• Make sure you have permission if you want to take a quantity of seaweed from a beach