I Buried Bananas and Fish Under My Tomatoes. Here's What Happened...

22 September 2025, written by Benedict Vanheems

There’s a long tradition of burying stuff under plants to give them a boost: compost and fertilizers for sure, but…fish and bananas?

Lots of gardeners swear by burying these beneath fruiting vegetables like tomatoes, but does it really work and – crucially – will you get a bigger harvest? That’s exactly what I wanted to find out this spring, and now I’m going to reveal the results of my gardening experiment! But first, let’s hop back to the start…

The Fish and Banana Experiment

My experiment was carried out on three tomato plants, all the same age and the same variety to enable me to fairly compare the results; the only variable was what was planted beneath them.

Underneath tomato one I planted some fish (in this case a few tins of sardines); beneath tomato two, overripe bananas; and then the third tomato was our control, with nothing buried beneath it, so we have a standard tomato to compare against.

I planted the tomatoes in my greenhouse. They could equally go outside, but I wanted to reduce the chances of foxes or other animals digging up the fish. This happened to me last year, so I know it’s a risk!

Planting holes with fish in one, bananas in the second, and nothing in the third — Three holes for three tomatoes, one laced with fish, one with bananas, one with nothing. What will be the results?

The soil had been improved earlier in the season with plenty of well-rotted compost along with a few handfuls of bonemeal for good measure, which should help with root development to help settle the plants in. This meant the soil had been improved with some general nutrition, but it won’t last all season, and I anticipated seeing a pronounced influence courtesy of those bananas and fish. I planted each tomato nice and deep, in a hole twice as deep as the depth of the pots they were currently growing in, and about 18in to 2ft (45-60 cm) apart.

I chose sardines to go under my first tomato because this is what most people will have access to, but if you can find old fish heads and bones, all the better! If your sardines are in brine or oil, start by thoroughly washing them to rinse off the worst of the salt and oil.

Fish is rich in all the main plant nutrients – nitrogen, phosphorous and potassium – which are essential for sustained, healthy growth. The fish should rot down gradually over time, slowly releasing their nutrients to fuel growth and, hopefully, plenty of fruits! There’s also the benefit of calcium in the bones themselves, which should help to avoid issues such as blossom end rot. This technique has a long history, with the Native Americans known to have used fish as fertilizer, for example burying fish along with corn seeds to enrich the soil and speed plant growth.

Next, I covered the fish with a few inches of soil. Then I removed the lowest leaves from the tomato, because they would get buried when planting deeply, and planted it. The buried part of the stem should go on to produce additional roots, which will help to anchor the plant in place and suck up more nutrients. Nice one!

Cut-up bananas — Cutting up fruit to plant beneath tomatoes. Has Ben gone bananas?

Next, the banana-fed tomato plant. It would take much longer for the bananas to break down if I put them in whole, so I cut them up into smaller rounds. Like the fish, bananas are full of goodness – significantly potassium, which is the number-one nutrient to encourage prolific flower and fruit development. It’s often recommended to lay banana skins around tomato plants because of this, and many gardeners swear by steeping skins in water to produce a potassium-enriched liquid for watering onto their plants.

As before, I put the bananas into the bottom of the hole then covered with a few inches of soil before removing the lowest leaves of the tomato plant and planting it deeply.

And then, finally, the control tomato. I planted it at the same depth as our other two, but didn’t bury anything underneath this one.

With them all planted, I thoroughly watered them all in and thrust in their supports of sturdy bamboo canes. And then I waited…

Ripening tomatoes — After two months, all three tomato plants had ripening fruits

8 Weeks After Planting

After eight weeks, during which the tomatoes were not fed, only watered, all three plants looked pretty much the same. In fact, if anything, it looked like the tomato with the fish beneath it was lagging behind the others – possibly because the fish hadn’t broken down yet, and is a little bit harsh on the young roots.

The good news is that all three of tomato plants had fruits developing, no doubt aided by the unbroken stretch of warm, sunny weather we had.

Ripe tomatoes — Tomato plants nourished with fish scraps were the first to start ripening

10 Weeks After Planting

After 10 weeks, I harvested my first tomatoes. The tomato with the fish beneath started ripening first, but the others weren’t far behind.

First Picking

Fish: 338g (11.9oz)
Banana: 285g (10.1oz)
Control: 353g (12.5oz)

The banana tomato was lagging at this early stage, but I’d say it’s still a respectable first picking for all the tomato plants.

Over the course of the next month or so I continued to pick and weigh the tomatoes. The second picking was remarkable for how evenly distributed the ripe tomatoes where across all three plants. But by the next picking, just two weeks on, the fish and control tomatoes had slowed right down, leaving the banana tomato to dramatically jump ahead, making up for its slower start earlier in the summer.

The Results

The banana tomato made a slow start, perhaps because it took a while for the banana to start decomposing. But it then massively caught up, producing an average of 28% more tomatoes than the fish and control tomatoes.

I expected more from the fish, but the lack of discernible results may be down to a few things. Perhaps there simply wasn’t enough fish in a few tins of sardines to have much of an impact. If I was to try fish again, I’d aim to use lots of fish scraps from the fishmongers. Or, perhaps even better, simply apply fish in the form of a fish fertilizer. I made some this summer in fact, and have been very pleased with the results elsewhere in the garden.

Final Pickings

Fish: 908g (2 lb)
Banana: 1,225g (2 lb 11 oz)
Control: 1,005g (2 lb 3 oz))

Will I plant bananas beneath tomatoes again? Do you know what, yes, I think I will! It’s an easy, plant-based, low-impact and, crucially, very affordable way to give tomatoes a bit of a boost, as we’ve seen – though I’d still apply my usual liquid tomato feeds for completeness.

Ben with tomatoes — Bananas really do help grow more tomatoes!

Bananas, it seems, really can help tomatoes grow stronger and produce more fruits – and maybe fish can too, though my little experiment didn’t show that this time.

At the end I dug up the tomatoes and took a look to see what was left beneath. And do you know what? There was nothing – not a scrap! So it looks like both fish and bananas became thoroughly incorporated into the soil and their nutrients were taken up by the tomatoes.

So there we have it. Bananas, it seems, really can help tomatoes grow stronger and produce more fruits – and maybe fish can too, though my little experiment didn’t show that this time.