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I recently bought some green onions from the supermarket and decided to try replanting some of them in a planter box on my balcony. I saved the bottom 4-5 inches of three onions and planted them in Miracle Gro Potting Mix. They seemed to be growing well; in just a couple of weeks, two of them were fairly large and one of those two already had six leaves.

But then I tried harvesting a leaf from one of the onions yesterday, and it smelled very strongly of potting soil. The leaf itself didn't have any soil on it, and I washed it thoroughly before using it, but that didn't get rid of the smell. I used it in some fried rice, and while the other ingredients helped to drown out the soil scent, they couldn't mask it entirely. The dish definitely tasted off. I tried harvesting another leaf from another of the onions today and using it in another batch of fried rice, but it smelled and tasted just like the first.

The scent is unpleasant enough that I can't imagine this is what home-grown onions are supposed to smell like, so I'm guessing that I'm doing something wrong. I've never done any gardening before, though, so I'm not sure what the issue is. Is this not the right kind of soil to use for growing produce? The parts of these onions that I used before planting them tasted perfectly fine, so I don't think there's anything wrong with the onions themselves. And while the soil doesn't smell "good", it also doesn't smell bad for soil, or at least not to my untrained nose. It smells like what I'd expect fertilizer to smell like.

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  • The smell of the leaves was the same as if you opened the potting mix bag and smelled it? I planted garlic and tomatos, the leaves and anything green, smells basically like what it produces (garlic and tomato), I am not sure about green onions though... Would be interesting to test with the same batch, 2 different potting mixes.
    – M.K
    Jun 15, 2023 at 8:31
  • Besides fertilizer, is there anything else in that potting soil (hydrogel, for example)?
    – Jurp
    Jun 15, 2023 at 13:19
  • @M.K Yes, I've compared the smell of the leaves with the remaining bag of potting soil. The leaves smell like a mix of the potting soil and onions, but more soil than onion. Jun 15, 2023 at 19:37
  • @Jurp No, I didn't add anything to the soil other than tap water, and my tap water doesn't smell or taste especially strong. Jun 15, 2023 at 19:38
  • I was wondering if the soilless mix itself, not your water, contained additives other than fertilizer.
    – Jurp
    Jun 15, 2023 at 19:40

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I am a little distrustful of many commercial bagged potting composts. That said, last year I did need to buy some bags of compost for some new raised beds and the organic material that came out of the sweaty bags did smell somewhat peculiar but once left for a few weeks in the sun, that scent went away.

Can I assume that you bought the bag of compost, immediately tipped it into the balcony tub and then planted the spring onion shoots? It is perfectly possible that any organic component possessed some volatile odours that could have transferred to the onion clippings but I am confident it will will leave both the compost and the onions fairly soon and it will not repeat itself.

Just make sure the balcony tub has plenty of drainage in the the bottom so when you water the substrate, it drains through the pot. Do not over-water the substrate and I feel sure your next trimmings will be odour free.

Many commercial composts contain many ingredients but many I have encountered include a fair amount of spent mushroom substrate and the mushroom odours can be quite strong for the first 3 weeks but it soon goes.

if you like Arugula (Rocket) seeds are incredibly cheap, seed well, can even be used as micro greens and would be excellent companions to your spring (green) onions. If you are a keen cook, you might also find that old shop bought purple onions that have begun sprouting are great if buried in the tub and you can crop the green leaves from those too and I would predict that any of the old odours will no longer transfer into your veggies.

You could try another bunch of shop bought green onions, use the tops for food, then pop them into a glass of water on your windowsill for 5 days to let them root a little before planting them in the balcony tub. Then you can compare the difference. Use scissors to cut your greens and taste a tiny 1/4 ins (5mm) piece before using them for cooking to ensure there are no earthy smells or flavours.

Good luck

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  • PS: Have a look on the back of the bag potting mix - it has to by law specify what goes into it and you may have a clue as to what the smell is from the list of ingredients, or not of course knowing many manufacturers.
    – Nikki
    Jun 15, 2023 at 20:20

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