Why might seaweed and kelp be good for the garden?
Seaweed and kelp contain potassium, loads of trace elements, growth hormones and enzymes. It is believed that seaweed helps free up nitrogen in the soil that could be stuck from a lack of nutrient balance.
Where do I find seaweed and kelp?
At the seashore, at the grocery store or Asian market.
If convenient, I always try to collect a little seaweed after a trip to the beach. Once dried it stores wonderfully. Now that I’m caring for the school garden, I can always use seaweed for anything we’re growing.
Have you tried a healthy snack of dried seaweed? I thought my daughter would love it at school and failed to test it before I put it into her lunchbox. She hated it so I used it on my plants.
Which plants may benefit from seaweed and kelp?
I have a favorite – potatoes. Any plants that flower or fruit will get a kick out of seaweed’s growth enhancers and trace minerals. The image below shows potatoes at school planted in inexpensive polypropylene grow bags. The row closest to the raised bed was amended with seaweed and kelp. The four bags lagging behind did not have seaweed added at planting time.
I also like to fertilize my asparagus with seaweed. Asparagus has three stages of growth: harvest, fern and dormancy. In spring before spears emerge, I top dress the soil with kelp or drench it with kelp tea. Later on when it’s in the fern stage, I use fish. See the Fish Recipes for more advice.
Combine seaweed with…
Fish fertilizer or other materials rich in nitrogen such as alfalfa and composted chicken manure work well alongside seaweed. Do not over-apply nitrogen on plants that are about to blossom or go dormant.
There’s a misconception that seaweed contains too much salt to be put in the garden without rinsing. The salt in the seaweed contains nutrients and unless you are collecting truckloads of it and concentrating application in one area, year after year, the salt will not harm your garden – it may actually help.
Scientists have concluded that collecting a shopping bag of seaweed on the beach will not harm the environment or upset the ecosystem. The best place to collect seaweed is below the high tide line. The stuff sitting on drier land, up on the berm for example, gives wildlife protection and therefore should be left alone. That’s why I collect newly emerged seaweed and kelp. And I only collect small amounts at a time from areas that I assume are not polluted. To read more about the impact of large-scale seaweed and kelp harvesting, visit the Bibliography and look under the topic Seaweed.
Seaweed and Kelp Soil Amendment and Mulch Recipe
Collect a small amount of seaweed and/or kelp on the beach from below the high tide line. Use it fresh or dried, both types will improve our soil and feed microbes. Unless you know your soil is too salty, you do not need to wash seaweed before use.
Chop or cut it up if possible – the smaller the pieces, the more surface area available for soil microbes to work. I use 3 handfuls in every planting hole – that’s if I have enough.
Another option is to use it as a mulch. Large kelp leaves should be chopped or cut up first, otherwise the leaves won’t let enough air in.
Here’s a picture of one of my amazing tomato plants grown in an inexpensive plastic (polypropylene) grow bag. I got over 25 heirloom fruits from one plant. That’s incredible to me because heirlooms usually need a lot more space. I added kelp and eggshells to the planting hole, and amended with alfalfa pellets (alfalfa early in growth only).
Seaweed and Kelp Soil Drench Recipe
Let seaweed sit in a container with water for a day or two.
If you want to contain the seaweed for ease of use, place a few handfuls into a mesh bag or place whole pieces on the bottom of a bucket with a brick or rock on top.
For a 5-gallon bucket, I would use 4-5 handfuls of seaweed or kelp. Add water and let it steep for a day or two. Water your plants as usual around the drip line and put the solids in your compost or a planting hole.
You have the option of drying seaweed in the sun to keep for future use.
Seaweed and Kelp Quick Tips
- When applying liquid fertilizers as a soil drench, it’s best to water the soil first so that when you use the soil drench it will disperse properly into the soil.
- I never soak seaweed or other materials for weeks because I don’t think the stench, growth of bad bacteria and potential health concerns outweigh nutritional benefits. A solution created in two days may be weaker than one created in a couple of weeks, but in my opinion it’s still beneficial and a lot safer.