Seaweed is a wonderful addition to your garden. You can use seaweed you have harvested from your local beach (check whether there are any restrictions preventing this in your local area first though) or you can purchase powdered seaweed or a liquid seaweed extract.
Benefits of Seaweed in your Garden
Seaweed can provide a range of benefits to your garden depending on the form you use.
Powdered Seaweed and Liquid Seaweed Extracts
Powdered seaweed and liquid seaweed are both good sources of potassium (a primary macronutrient), magnesium (a secondary macronutrient) and a variety of micronutrients. They also contain plant growth hormones (also called plant growth factor) which, as their name suggests, improve plant growth.
Seaweed prevents transplant shock and stimulates root growth so it's always good to dose plants with seaweed at or before transplant time. It also increases the ability of plants to withstand environmental extremes such as drought and frost so it's a great tonic to apply in autumn and throughout winter in frosty areas (particularly on slightly tender species or when there is an unusually severe cold snap) and during summer in hot areas.
Using Powdered Seaweed and Liquid Seaweed Extracts
Powdered seaweed can be incorporated into the soil before planting and used as a side dressing when required. In this respect, it is much like any other solid fertiliser you might use on your garden.
Liquid seaweed extracts need to be diluted (follow the instructions provided by the supplier) and can be used like any other liquid fertiliser and/or as a foliar spray. Seedlings and established plants can also be soaked in seaweed solution prior to transplanting (just half fill a bucket with the diluted solution and leave plants to soak for 15 minutes or until bubbles are no longer released from the potting mix if they are in pots). The solution can then be used to water in the plants when they're in their new position.
Raw seaweed bestows the same benefits as other forms of seaweed but if you can obtain seaweed straight from the ocean, it also makes a great soil conditioner and is a good form of organic matter so it attracts worms.
Preparing Raw Seaweed
Because seaweed comes from the ocean, it can be quite salty and too much salt can be bad for your soil and plants. So to use seaweed straight from the ocean you'll want to wash it thoroughly to remove the salt. You may also want to chop it up so that it breaks down more quickly in your soil but that's optional.