Are you wondering if using liquid seaweed fertilizer really improves the health of your herbs? Find out the benefits and how to use seaweed to help your herb plants grow stronger and healthier in the garden.
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Seaweed extract is an organic fertilizer that provides micronutrients for your plants. All herbs, even those that don’t need a lot of nitrogen fertilizer, can benefit from seaweed.
And if you live near the ocean, you may be able to make your own seaweed fertilizer.
Benefits Of Using Seaweed Fertilizer
One of the most recommended types of fertilizer for feeding your herbs is seaweed. Not only is it naturally sourced, but it is gentler on our herb plants than most other commercially available products.
Often fertilizer is discussed in terms of the Big Three nutrients: nitrogen, phosphorus, and potassium, or NPK. These are the three numbers that you’ll find on bags of fertilizer. Seaweed has plenty of K and very little of the other two. For example, Fedco Seeds lists their powdered seaweed extract at 0-0-18.
Seaweed also contains many essential micronutrients that aren’t measured in the Big Three numbers.
The Rodale Institute discusses the benefits seaweed can provide to organic farms. The seaweed provides plants with proteins, amino acids, vitamins, sugars, and more that all work together to improve the fertility of the land.
Giving seaweed extract to your herbs (and other plants) will strengthen them against pests and make them better able to fight off disease.
If you compare this to how people need not only proteins and carbs but also vitamins and antioxidants in order to thrive and bounce back from sicknesses, it makes sense.
In my own garden, I’ve also gotten into the habit of spraying plants that I’ve set out early before we get a late frost. Something about the micronutrient boost seems to help them bounce back better from that as well.
How to Use Seaweed to Feed Your Herbs
Liquid seaweed fertilizer can be watered into the soil or sprayed onto leaves. Foliar feeding gives the quickest nutrient boost and the most “bang for your buck,” so I always use seaweed as a foliar feed.
I dilute my seaweed powder according to the instructions on the package. If I’m using a mix with fish emulsion, I mix it outside so that I don’t stink up the house–fish emulsion can have a rather potent smell. In my experience seaweed extract, itself is fairly odorless.
Some sources recommend adding something to help your seaweed extract stick to the plants. Fish emulsion will take care of that if you’re using a mix. Fedco suggests adding ½ teaspoon of soap per gallon of water to plain seaweed to help with sticking. I’ve just used my seaweed spray straight, and I am still satisfied with the results. If you buy a ready-to-use spray it may already contain something to help with sticking.
Rodale’s recommends spraying most herbs with seaweed twice or thrice during the growing season. I tend to spray mine monthly. I also spray with seaweed when I am concerned about pest or disease problems or ahead of frost.
Can You Harvest Your Own Seaweed For The Garden?
If you’re lucky enough to live near the coast, you may be able to harvest your own seaweed for fertilizer. I have a friend in coastal Maine who takes his family to the beach in the fall to rake in seaweed and bring it back to spread as mulch on their garden beds.
Seaweed mulch is best applied in fall, not during the growing season.
You can also use locally harvested seaweed to make liquid seaweed fertilizer. Then you will have your own supply to feed your plants throughout the growing season. Mother Earth News recommends this process:
- Rinse seaweed to remove excess salt
- Pack a bucket as full of rinsed seaweed as you can. Cover with water. Put a lid on.
- Leave for at least eight weeks, stirring every few days.
- Drain and strain the liquid into labeled containers
- Use a ¼ to 1/2 cup of seaweed extract in 2 gallons of water if you’re watering it in at the roots. If you’re foliar feeding, use two tablespoons of seaweed extract to a gallon of water.
Before you do harvest seaweed from the beach, make sure you find out what the local rules and regulations are. Ask what areas are open for public collection and whether there are protected types of seaweed, you should not be harvesting at all. In some areas, you may also need to ask about pollution and contamination. Your county Cooperative Extension can probably help you find this information.
Even if there are no regulations, only harvest seaweed that is lying at the high-tide line, rather than pulling up live rooted seaweed. Always leave more than you take away.
Buying Seaweed Fertilizer
Inlanders like me have to buy seaweed fertilizer instead of harvesting it. I get a powdered seaweed solution which I mix with water as needed and use as a foliar spray.
You can also buy either liquid concentrate or liquid ready-to-use seaweed spray. Make sure you know which you have! Seaweed spray, like any other growth aid, can do more harm than good if you give extremely high doses of it.
Many organic supply stores also offer a mix of seaweed and fish emulsion. The fish emulsion is high in nitrogen and phosphorus (exact values vary depending on the specific preparation).
I use fish/seaweed mix on heavy feeders in the vegetable garden and sometimes also on my basil. Most of my herbs just get straight seaweed without fish, since many of them have better flavor if they don’t get too much nitrogen and phosphorus. [Link to article on fertilizing herbs]
Seaweed is a relatively cheap organic fertilizer whether you buy it or make your own. When applied during the growing season, it can improve the health and resilience of your herb garden.
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