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Seaweed collects valuable nutrients from the water and rich soil found in freshwater bodies of water such as lakes and ponds. These aquatic plants can transfer some of these nutrients to your garden, helping your plants grow and produce an abundance of fruit or flowers. Take the proper steps to collect, prepare and use the seaweed.

Saltwater vs. Freshwater Seaweed The term seaweed typically is reserved for aquatic plants that grow quickly or invasively. Freshwater and saltwater seaweed often offer many nutrients to your soil such as nitrogen, but freshwater seaweed has an advantage over its ocean counterpart: it doesn't contain salt. Too much salt can change the salinity of your soil and keep your plants from prospering. Because freshwater has little to no salt content, the seaweed that grows there doesn't add salt to your garden.

Finding Freshwater Seaweed Many garden supply stores offer fertilizers that contain seaweed, including foliar sprays and granular fertilizer mixes. However, taking advantage of fresh seaweed means taking a quick trip to your local lake or pond. Many local governments have ordinances that govern how to collect freshwater seaweed -- usually that you can you pick up what has washed ashore. Others have teams who collect the invasive weeds and supply them to gardeners for a small fee, while some let you cut your own from where it grows in the water. Check with local authorities to ensure you're following the proper procedure.

Composting Seaweed Freshwater seaweed works best when composted before adding it to your garden, although you can simply lay the long strands over your soil if you prefer. To compost the seaweed, drain it well or lay it over raised pallets to dry before adding it to your compost pile. If you're adding damp seaweed, mix in substances such as dried leaves, grass or hay to help keep your compost pile at the proper moisture levels. Turn seaweed into the rest of the compost pile and use it in your garden along with your normal composting process.

Applying the Seaweed Compost Seaweed offers the benefit of not containing weed seeds that can germinate on land, so it's a helpful amendment to your garden. But always place seaweed compost in areas that don't run off into nearby freshwater bodies -- it can still contain viable seeds that could spread the invasive species into new lakes and ponds. In garden beds that aren't near water, spread the compost 4 to 6 inches deep around your plants to use as a mulch or turn it into the top few inches of soil as an amendment.