Free Seaweed Fertilizer

Consider using seaweed or pond weed as a garden soil amendment

REGULAR readers of SHF know by now that I hate to pay for garden soil amendments like bagged compost or fertilizer. One way I’ve found to get good, free fertilizer is to harvest seaweed for your garden or compost pile.

If you live near the coast, seaweed can be free for the taking. If you don’t, pond or lake weed can provide some of the same benefits of seaweed fertilizer.

Too much salt

When the subject of seaweed fertilizer comes up, many gardeners are concerned that it will add too much salt to the soil. My experience has shown that even if you add seaweed regularly, this is not the case, especially if you compost the seaweed first. Composting dilutes the salt as the seaweed combines with other materials. It also lets the salt leach off naturally.

That said, there is one important consideration when it comes to seaweed and salt. Worms don’t like salt. When I add seaweed to a compost pile, worms disappear. They probably find it toxic. So if you want to encourage worms, keep seaweed to a minimum.

Another important point is that seaweed breaks down very fast in the compost pile and, if your seaweed has sand in it, you probably will see pockets of sand in your compost where the seaweed has decomposed but the sand remains. Keep in mind that some sand in your garden is not bad. It will help drainage and add missing nutrients, but some people suggest taking only seaweed that has little to no sand mixed with it.

Speaking of compost piles, seaweed makes for a great compost pile activator. Experts believe this is because it naturally promotes microbial life. One possible reason for this is that some seaweed is very high in nitrogen and many compost piles lack the necessary amount nitrogen to keep a compost pile humming.

Seaweed Fertilizer

Many gardeners don’t know that seaweed fertilizer will discourage worms from staying in your soil.

Seaweed fertilizer at a glance

  • Inhibits certain insects and pests
  • Increases flower production & yield
  • Protects plants from frost
  • Increases root mass
  • Promotes better soil texture
  • Acts as a compost activator
  • Mulches with no weed seeds

According to noted farmer and author Eliot Coleman, seaweed improves sandy soil by adding the glue that helps bind soil particles together. Of course, if sand is included with the seaweed, this will counteract the seaweed’s binding properties.

Coleman especially likes seaweed for plants like tomatoes and potatoes. He adds it directly to the soil in fall and leaves it exposed to the elements all winter. Then, he mixes it with the soil, adding organic matter to his clay soil and stimulating microbial activity. This is the traditional approach used by gardeners on the Maine coast.

Bigger roots

Some researchers have found that seaweed extract helps plants grow larger root systems. For example, tomato plants on seaweed extract grew 80 percent more root mass than untreated plants. In addition, seaweed extract helped to improve the cold tolerance of tomato plants. They endured temperatures as low as 29 degrees Fahrenheit.

This is why some experts believe that adding seaweed to a planting hole for potatoes, tomatoes, asparagus or rhubarb is an excellent way to supply seaweed fertilizer to the roots, thereby giving these plants a good start.

Other expert growers believe that seaweed prevents slugs and other soft-bodied pests because it forms small razor-like edges in the soil after it dries. Salt may also plays a role in pest prevention. If worms don’t like the salt, it’s probably true of other small creatures.

Too far from the coast

If you don’t have easy access to seaweed or pond weed, the next best thing is store-bought liquid seaweed extract. Of course buying liquid seaweed fertilizer isn’t free, but it has some advantages. Probably the best one is that’s it’s very easy to apply. Another is that you can use it for foliar feeding as well as a soil amendment.

Keep in mind, however, that some seaweed extracts are mixed with fish solutions. These combined products can be very effective fertilizers, but there can be problems. My own experience is that skunks and other creatures will pull plants right out of the ground when they smell a fish buried under your plants. You will want to make sure you have adequate fencing if you use a liquid fertilizer that includes fish.

Take these precautions when using seaweed fertilizer

  • Never use live seaweed – You may damage the ecosystem. Use only dead seaweed. Exception: You can use live pond weed if it is an invasive species, such as milfoil, but you must be sure not to spread it to uninfected areas and knowing good pond weed from bad is pretty near impossible.
  • Make sure it’s legal – Harvesting seaweed is not allowed in some areas. If you are unsure, check with authorities.
  • Use pond weed – If you want to encourage earthworms, don’t use seaweed. Salt from the seaweed drives worms away.

Have you used seaweed in your garden? How has it turned out for you? Let us know by commenting below.

Articles you might enjoy:

1. 5 Gardening Ideas from Building Soils Naturally
2. Product Review: Neptune’s Harvest Fertilizer
3. Comfrey Mulch for Strawberries

Article Name
Using Free Seaweed Fertilizer in Your Garden
Article on harvesting and using seaweed fertilizer or pond weed in your fruit and vegetable garden. But DON'T use it if you want to encourage earthworms.



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