Updated: February 4, 2020
I’ve been using Neptune’s Harvest liquid fish and seaweed fertilizer for about 10 years now. So I can tell you with out a doubt that Neptune’s Harvest provides a fast acting boost for your leafy green plants.
This is especially true of tomato plants. It works well when plant growth is stalling due to inadequacies in the soil.
Let’s take a sec to get the legal words out of the way. This article may contain affiliate links. That means if you click and buy from my partners, I will make a tiny amount of money. This in no way affects my recommendations.
But Neptune’s Harvest has some short comings. For example, the Neptune’s Harvest people would have you believe that it smells like a day at the beach. That isn’t exactly true.
That’s not to say that I don’t recommend Neptune’s Harvest. I found that it works exceptionally well, encouraging dark green leaves and leaf growth on a number of my favorite garden plants. In addition to tomatoes, I use it with strawberries, zucchini, cucumbers and more.
How I use Neptune’s Harvest
I use it when I want to encourage growth of both established plants and seedlings (but only after the danger of dampening off has passed). Although, when I use it on seedlings, I dilute it to half strength to avoid burning the tender plants.
As you might expect, Neptune’s Harvest is derived from fish and seaweed. Mostly, it’s used as a fast-acting soil additive that’s mixed into the water when watering your plants.
Related: How to Use Chicken Manure Pellets in Your Garden
Some people apply it directly to plant leaves for foliar feeding. It works primarily because it adds nitrogen in a form that is easy for leafy plants to digest.
From my research, I’ve learned that there are several kinds of liquid fish fertilizer. These include hydrolyzed fish emulsion and fish fertilizer, which are not the same thing. If you want to get into the technical differences between the two, see this page from The Organic Gardener on fish emulsion.
All of these products are OMRI Listed approved for organic gardening.
Neptune’s Harvest also offers both seaweed only fertilizer and a hydrolyzed liquid fish fertilizer.
I found NH’s fish and seaweed mix to be very economical. I paid very little for an 18 ounce bottle that has lasted me about two years. It can be hit or miss finding it at local garden centers and a pretty unlikely find at big box stores.
Normally, I would encourage readers to make their own soil amendments, but just the thought of making fish and seaweed fertilizer turns my stomach. Here’s a video on how one person makes a fish fertilizer and compost tea mixture.
I must say that I found this video of this lady casually talking about something as awful as blending fish in a food processor completely ironic — but also a bit captivating (in a car accident on the highway type of way).
One thing’s for sure, I’ll never try it. My recommendation: don’t do this at home.
Downsides to consider
There’s only a couple of downsides to consider when using the product as directed.
First, don’t get any on you if you can help it because the smell is terrible. Plus, it doesn’t come off easily.
Second, when I used it on tomato and cucumber seedlings, I found that an animal — probably a skunk — dug up the plants thinking that there must be something good’n fishy to eat buried in the ground .
Related: I Shopped for Cold Frame Kits. Here’s a Review of the One I Bought
Let me tell you, it’s kind of sad to see a newly planted seedling pulled out of the ground. So if you have animals around that will enjoy the smell, you might not want to use this fertilizer … or at least use the seaweed only version.
An alternative to Neptune’s that is pretty popular is Alaska Fish Fertilizer. I haven’t tried it, but you may want to look into it. I hesitate to try a product when I can’t easily figure out who manufactures it.
Other articles you might find interesting:
- Transplant Seedlings at Proper Soil Temperatures
- Getting Rid of Gnats on Seedlings
- I Tested the Top 4 Seed Starting Mix Products. This is What I Learned
Suburban Hobby Farmer is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.