The Oldest Fertilizer Trick in the Book: Why You Should Bury a Fish in Your Garde

There's a good chance you've tossed fish scraps in the trash without a second thought. A leftover salmon head here, some sardine bones there — straight into the bin. But for centuries before synthetic fertilizers even existed, Indigenous farmers across North America knew something we've largely forgotten: that a buried fish is basically a slow-release superfood for your soil.

This isn't some fringe gardening trend or internet rabbit hole oddity. It's one of the oldest agricultural practices on the continent, and it works.

Where This All Comes From

If you went to elementary school in the U.S., there's a decent chance you heard some version of the story about Squanto. He was a Wampanoag man who, in 1621, helped the struggling Pilgrim colonists at Plymouth by teaching them to plant corn — and specifically, to bury a fish alongside each seed. The colonists had been farming soil that was, by many accounts, depleted and sandy. The fish changed everything. According to Indian River Organics, following Squanto's advice, the colonists grew so much maize that it became the centerpiece of the first Thanksgiving.

But this wasn't just a Wampanoag thing. The Mayans did it. The Incas did it. Tribes in the Pacific Northwest buried salmon carcasses in their garden plots. The Romans reportedly used fish in their soil too. The practice is so widespread across independent civilizations that you have to wonder if they were all onto something — and they were.

Traditional Native American growers buried fish under mounded soil and planted the Three Sisters — corn, beans, and squash — directly on top. They didn't need a soil science degree to understand cause and effect: bury a fish, grow a better crop.

What's Actually Happening in the Soil

Here's the science behind why it works, because it's worth understanding.

As the fish slowly decomposes, it feeds the crop throughout the entire growing season. The breakdown process releases four key nutrients that plants are absolutely hungry for:

Nitrogen is the big one. As the protein breaks down in the buried fish, it releases a lot of nitrogen, minerals, and vitamins beneficial to growing vegetables like tomatoes, peppers, and cucumbers. The proteins aid growth of foliage and roots and promote vigorous blooms. If your plants are looking pale and spindly, nitrogen deficiency is often the culprit — and fish delivers it in a slow, steady, burn-free way that synthetic fertilizers can't always replicate.

Phosphorus is essential for flower and fruit development. Without it, your tomato plants might look green and healthy but never set fruit worth eating.

Potassium supports strong root systems and overall plant vigor — the kind of resilience that helps a plant push through a dry week or shrug off a pest problem.

Calcium is the underrated one. Unlike synthetic fertilizers, fish fertilizers may also provide secondary nutrients such as calcium. Plants that receive a balance of primary and secondary nutrients experience strong and steady plant growth, leading to stronger plants that can better withstand disease and pest issues. Calcium deficiency is what causes blossom end rot in tomatoes — that frustrating black patch on the bottom of an otherwise perfect fruit.

The other thing fish does that a bag of synthetic fertilizer cannot is feed the biology in your soil. Worms, fungi, bacteria — all of them thrive when you add organic matter. A living soil is a productive soil, and fish turbocharges that whole ecosystem.

What Kind of Fish Should You Use?

Almost any fish works. The most commonly used species include salmon, trout, herring, and menhaden — but honestly, you don't need to be picky. The fish you don't eat is the fish you bury. Heads, bones, guts, tails — all of it is fair game. If you fish regularly, this is a genuinely fantastic use for the parts that would otherwise go to waste.

Don't feel like you need to run out and buy whole fish for your garden. Leftover bits from cooking work perfectly. A salmon head you weren't going to eat anyway, sardine cans that have been sitting in the back of your pantry — all useful.

How to Actually Do It

This is simpler than it sounds, but there are a few things you want to get right.

What You'll Need

• Fish scraps, whole fish, or fish heads/bones/guts
• A shovel or garden trowel
• Optional: cayenne pepper, chicken wire, or a fenced garden

Step 1: Dig Deep Enough

This is the part most people get wrong. Due to constant issues related to animal pests like raccoons and rats digging up your buried fish fertilizer, you need to bury it at an ideal depth of 1 to 1½ feet down, beside or under each plant. If you've ever had a raccoon tear up your garden at 2 a.m., you'll understand why this matters.

A shallow burial — say, 4 or 5 inches — might seem like enough, but it won't be. Dogs, raccoons, foxes, and cats have noses that can detect buried meat through a foot of dirt. The deeper you go, the safer you are.

Step 2: Place the Fish

Lay the fish (or fish scraps) at the bottom of the hole. If you have a whole fish, you can cut it up a bit to help it decompose faster. If you're doing this at planting time, place the fish at the bottom, then add a few inches of soil on top before placing your seeds or transplants. You don't want your seeds in direct contact with the fish — they need a buffer of soil between them.

Step 3: Cover It Well

Pack the soil back in firmly and mound it slightly over the top. This helps prevent anything from digging down. You can also wrap and bury the fish in newspaper, or even bury it while frozen, so it's well under the surface before it begins to decompose and release any smell. The frozen trick is particularly clever if you want to reduce odor near the surface.

Step 4: Deter Pests

Even with a deep burial, it's smart to take extra precautions. Sprinkle cayenne pepper generously around the planting area — most animals hate the smell and will avoid it. If you have a fenced garden, you're already in good shape. If your garden is fenced so that nothing can dig them up, you can even bury fish heads, guts, and bones at the time of seed planting, or just prior to it.

Some gardeners also lay a piece of chicken wire flat over the burial site for the first couple of weeks until the smell dissipates underground. Low-tech, but effective.

Step 5: Be Patient

The release rate is slow for fish fertilizers compared to other types — which is actually a good thing. You don't need to apply it often. Unlike synthetic fertilizers that dump everything at once and can burn roots, fish breaks down over weeks and months, feeding your plants through the whole growing season.

A Few Things to Keep in Mind

Timing matters. Bury your fish at planting time, or a few weeks before, so decomposition is already underway when your plant's roots reach that depth.

Don't go overboard. One fish or a handful of scraps per plant or per square foot is plenty. More isn't always better — too much organic matter breaking down at once can temporarily pull nitrogen away from plants as the soil bacteria work to process it.

Urban gardens and close neighbors. If you live in a densely packed neighborhood, be smart about odor. A deep burial and the frozen trick will help significantly. The smell, if any, really does stay underground once you get past that first week.

It's a one-time-per-season deal. Unlike liquid fertilizers you apply every few weeks, a buried fish just does its thing slowly through the season. Plant it and forget it.

The Bigger Picture

There's something satisfying about using a practice that's this old. We spend a lot of time chasing the newest gardening products — the latest soil amendment, the trendiest supplement. But here's a technique that the Wampanoag, the Iroquois, the Mayans, and the ancient Romans all figured out independently, with nothing but observation and a willingness to experiment.

And modern soil science confirms they were right. The nutrients are real. The biology is real. The results are real.

As the buried fish slowly decomposed, it would release essential nutrients into the soil to feed the growing plants — a practice so foundational that it now serves as the basis for modern fish emulsion fertilizers.

So the next time you're cleaning a fish, or emptying a tin of sardines into a pasta dish, maybe set the scraps aside. Your garden has a use for them.