Daily Survival: Why You Should Bury Fish Heads Under Your Crops This Fall

The first time I buried a fish head in my garden, I did it lazily and shallowly, and the dog had it dug up before dinner. The second attempt went deep. By August that tomato plant stood a foot taller than the ones on either side, carrying fruit heavy enough that I had to stake it twice. Everything else about that bed was identical. Same seedlings, same watering, same compost worked in that spring. The only difference was a bluefish head sitting a foot and a half under the roots, quietly turning itself into plant food.

Farmers figured this out long before fertilizer bags existed, which is why the story about Squanto teaching the Pilgrims to bury fish with their corn still gets told every Thanksgiving. The technique goes back further than that on both sides of the Atlantic, and it runs completely independent of any supply chain.

What’s Actually Inside a Fish Head

Break a fish head down into its parts and you can see why it outperforms most of what comes in a bag. Every piece of it feeds the plant differently, and they release on different schedules, so one head covers a lot of ground.

Nitrogen from the flesh, gills, and brain. Protein means nitrogen, and commercial fish meal runs somewhere around 9 to 10 percent by weight. That puts it in the same league as blood meal and well ahead of finished compost.
Phosphorus and calcium from the skull and jawbones. Bone is calcium phosphate, so you’re burying a slow-release phosphorus source right where the roots will find it. Phosphorus drives flowering and fruiting, and it’s usually what’s missing when a plant grows lush and green but never sets much fruit.
Months of feeding instead of weeks. Bone breaks down far slower than soft tissue, so a single head keeps working long after the flesh is gone.
Oils that feed the soil itself. Fish oils feed bacteria and fungi, which in turn unlock other nutrients already sitting in your ground.
Trace minerals inland soils often lack, including iodine, magnesium, zinc, and selenium. Ocean fish are the better source here, since that’s where those minerals came from.
Amino acids as a mild growth stimulant. As the protein breaks down it releases them straight into the root zone, so you get a small boost on top of the nitrogen.

Potassium is the one gap, since fish is low in it. That’s why it pays to pair your buried heads with wood ash, banana peels, or a bit of kelp if your soil test comes back short.

You know what else you can do with fish heads? You can protect your crops of insect pests with this DIY trap:

Test Your Soil Before You Dig Anything

Before you put a single fish head under your tomatoes, make sure you do the mason jar soil test on that bed first, since it takes twenty minutes and a jar of water and it tells you whether your ground is sand, silt, or clay.

The soil test answer decides how deep the fish goes, since clay traps the salt while sand flushes it straight past your roots.

So once you know what you’re working with, these are the rules that decide whether the fish feeds your plants or ruins the bed:

Twelve to eighteen inches is the target. Anything shallower and something will smell it and dig. Anything deeper and the roots may never reach it.
Keep three to four inches of plain soil between the fish and the roots. Fresh fish decomposing right against a root ball releases ammonia and heat, and young roots will burn. Bury the head, backfill several inches, then set your transplant on top of that buffer.
One head per plant is plenty for anything tomato-sized or larger. Two or three smaller heads work if that’s what you’ve got.
Chop bigger heads in half if you’re dealing with something like a tuna or a big salmon. A whole large head can take most of a season to break down and may go anaerobic and sour instead of decomposing cleanly.
Skip it in soggy ground. Waterlogged soil has no oxygen, so instead of breaking down, the fish just rots and stinks. Raised beds and well-drained ground are where this shines.

If you’re doing a whole row rather than individual plants, dig a trench a foot and a half deep, lay the scraps along the bottom every eighteen inches or so, and backfill. Corn rows take beautifully to this.

Four Crops You Should Never Put Fish Under

Heavy nitrogen feeders are the obvious winners. Tomatoes, corn, squash, pumpkins, cucumbers, peppers, and the whole brassica family all respond hard to a buried head. So do fruit trees and berry canes, though those want the scraps out near the drip line rather than against the trunk.

A few crops you should leave out of it:

Root vegetables like carrots and parsnips will fork and split when they hit a rich pocket of decomposing matter.
Beans and peas fix their own nitrogen and don’t need the help. Extra nitrogen just gives you vines with hardly any pods.
Herbs like rosemary, thyme, and oregano actually taste better in poor soil. Feed them heavily and you get big, bland plants.
Garlic and onions can handle moderate feeding but tend to grow soft, poor-storing bulbs if you push nitrogen too hard.

Why Fall Is the Best Time for This

Warm soil breaks a fish head down in roughly four to eight weeks. Cold soil can take months, and in frozen ground nothing happens at all until thaw.

That timing works in your favor if you plan ahead. Bury your scraps in fall, and by the time you’re setting out seedlings the following spring, the soft tissue is gone and the nutrients are already spread through the soil where roots can grab them immediately. Spring burial still works, it just means your plants wait a few weeks before they see the benefit.

8 Things to Do This Fall to Winter Proof Your Garden

Don’t have fish in the fall? Freeze your scraps as you get them. A gallon bag of frozen heads in the back of the chest freezer costs you nothing and gives you a stockpile ready for planting day.

Watch Out for Raccoons and Bears

Anything with a nose is interested in what you just buried, and a raccoon that finds one fish head will come back and work through the rest of your garden methodically. Depth is your first line of defense, but in areas with heavy critter pressure you’ll want backup, and the Three Sisters System handles that problem for you.

A flat rock laid over the spot also works, and so does a square of chicken wire pinned down with landscape staples, since that lets water and roots through while stopping paws. Some homesteaders pack a couple inches of coffee grounds or wood ash over the fish before backfilling, which muddies the scent trail.

Bears are a different conversation. If you’re in bear country, keep fish out of the garden entirely and use a sealed compost tumbler instead, because a bear that learns your garden smells like food becomes a permanent problem.

Turning Scraps Into Liquid Feed

Once your plants are in the ground, you can’t bury things under their roots. That’s when fish scraps become a liquid feed instead.

Fill a bucket about a third of the way with fish heads, guts, and frames, then top it with water and stir in a few tablespoons of molasses to feed the bacteria and cut the smell. Cover it loosely, since it needs to breathe, and park it somewhere far from the house and downwind. Stir it every few days. In two to four weeks, you’ll have a dark, foul liquid that’s finished fermenting.

Dilute it well before using, roughly one part liquid to ten parts water, and pour it at the base of your plants. Some people strain and spray it on leaves, though the smell hangs around for a day or two afterward. What’s left in the bottom of the bucket goes straight into the compost pile or gets buried in an empty bed.

But, as I said before, fish heads are short on potassium, so pair them with this homemade booster fertilizer. You need only six ingredients, costs nothing and takes about ten minutes to make:

Mistakes That Could Kill Your Plants

Piling on too much. Half a dozen heads under one tomato gives you a seven-foot plant with beautiful foliage and almost no fruit. Nitrogen overload pushes leaves at the expense of everything else.
Using heavily salted fish. Salt cod, brined scraps, and anything cured will load sodium into your soil and stunt growth. Fresh or frozen only.
Ignoring saltwater residue in clay soil. Ocean fish carry some salt naturally. Sandy soil flushes it out with rain; heavy clay holds onto it, so go lighter on the quantity if your ground drains poorly.
Burying scraps in a bag. Plastic mesh from the fish counter doesn’t break down and creates a barrier. Everything goes in loose.
Setting the transplant directly on the fish. Worth repeating, because it’s the most common way people lose a seedling doing this.

No Fish Heads? Use This Instead

Wood ash and urine together do most of what a fish head does, and the Rich Earth Institute has field trials showing urine fertilizer matches synthetic fertilizer of the same nitrogen content.

Work a cup or two of wood ash into an empty bed for the potassium and calcium, then hold the urine until your plants are past seedling stage. Their rate for a 10 by 10 bed is 3.5 to 5.5 gallons across the whole season, diluted one part urine to three or five parts water, poured into a furrow four inches from the base and covered with soil.

Never spray it, since urea turns to ammonia gas the moment it hits air. And don’t mix the two in a bucket. Rich Earth says ash makes the ammonia more volatile, so both go in separately.