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Growing where there has been a bonfire?

Good evening! My fiancé and I bought a house last year with a large (and very overgrown!) garden - we are really excited to have started growing flowers, herbs, fruit and veg. I’ve always loved gardening and the outdoors but it’s the first time I’ve had so much to do and it’s all a learning curve. I thought I’d join the forum for tips, advice and shared experiences.  :)

In our garden is a large heap, almost circular and maybe 4m across at the widest point, where a previous owner had multiple bonfires. The heap was full of complete junk including metal, plastic, glass and wood - we have cleared much of it and are digging it over and using a large magnet to pick up nails, screws and so on. It’s very sterile (no worms!) and the soil is quite grey and red in places, a bit rusty and ashy essentially. Is it safe to grow edible things here? My plan is to clear it as much as possible and then stuff it full of well-rotted horse manure. It gets some morning sun and then late afternoon but is in the shade during the sunniest part of day - was thinking perhaps to plant squashes there? It’s a large space and I’d hate to waste it!

Thank you very much. 


  • WoodgreenWoodgreen Posts: 1,273
    Hello @squidgyholly and welcome to the forum.
    What a good idea, using the magnet!
    Personally, I would not grow edibles there, as there may be toxic residues from whatever has been burned.
    You could use it to grow comfrey to add to your compost heaps/bins or to make a liquid feed. Trying the comfrey will give you some idea of whether or not the soil is fit to grow anything. I don't know if time, weather, and cultivating might eventually reduce any toxins, but if you found that even comfrey wouldn't grow, it may be a case of removing that soil and replacing it with fresh.
    I have come across old bonfire sites here, but not where I've wanted to grow edibles. It has needed compost adding, and mulches, but has improved in texture to grow ornamentals.
    Others may have more advice but I would be cautious about the ground.
  • nick615nick615 Posts: 1,481
    squidgyholly  One ray of hope?  Fire mainly burns UPwards, so the pile you've inherited will be ABOVE the original ground level, pre-fires.  Whilst not ignoring Woodgreen's advice, you may like to see whether you can scrape off the 'heap' and dispose of it somewhere, thereby at least reducing the risk of nasties in the original soil below.  A small mini-skip could be the answer, and thereafter await the arrival of worms to give you a clue?
  • Thanks for your replies! It’s a bit of an awkward spot for a pond but I have a pond in mind for a different area, thanks for the thought.

    A neighbour told me that the previous owner wouldn’t have had bonfires there and so it was likely the owner before that, meaning it was 20+ years ago. I can’t say if that’s true or not though of course! I think you’re right that we probably need to try and dispose of some of the top layer and perhaps avoid the edibles, darn it 🤔 Hadn’t considered comfrey so will look into that! We do have a good compost heap on the go. 

  • Here’s what we are working with.
  • If it really was 20yrs ago and the ground is still sterile with no worms etc that would really put me off growing anything edible there.
  • WoodgreenWoodgreen Posts: 1,273
    It might be an idea to remove the red and grey ashy material if it's still largely intact. If the fires had been merely branches, roots etc it would be a different thing, but people used to burn all manner of 'rubbish', rather than pay for it's removal, not realising the harm it could do to the environment.
    Some of the bonfire sites here are over thirty years old but when I dig there it's not like normal soil until it's been dug well, with compost added (and the remnants of unburned material removed.) I suppose turning the compost in encourages the earthworms.

    Have just seen your photo, and it doesn't look as bad as I'd imagined.
    It's possible some previous occupant burned a dismantled shed there, or old doors from the house ( hence the fixings you found.) But it's impossible to know. The mound looks as though it has soil incorporated into it, but the red/grey description would worry me after all these years.

    Was the heap covered in weeds, grass etc? 
  • When we arrived the heap did have some weeds on it but it also had a lot of larger pieces of junk as well, like broken flower pots, plastic bags and so on which had prevented some parts from growing. There was also chicken wire over some of it too, no idea why! It was also mostly shaded due to two larger trees which sadly had to come down (no longer safe) which were smothering the heap a bit.

    The photo (sorry it's sideways!) is after many hours of sifting through it and removing a lot of stuff, everything from large chunks of metal to hundreds of nails, bolts, bits of broken glass... some scraps of material, drinks cans, shower gel bottles, bits of shoe and more. When I run the magnet through it some particles stick to it, presumably rusty bits, which unnerves me a little bit. I am now finding the odd worm, grub and bug creeping into the outskirts but the middle was quite compacted... now it's loosened up I do think it'll come good. Maybe I just need to be patient? I could try to grow some native wildflowers on it this year but might be a bit shady. 
  • squidgyhollysquidgyholly Posts: 11
    edited April 2022
    Hoping these pics come out the right way around! 
  • WoodgreenWoodgreen Posts: 1,273
    You have done a good job of removing all the rubbish, and I can appreciate why you might want to make use of the soil now.

    I think you'll get plants to grow there if you incorporate as much organic material as you can, but it's a mound, and you may not want to keep that, or scatter it further out over the grass.

    I wouldn't think the particles of rust would be harmful, I'd be more concerned about not knowing what had been burned and dumped there over the years.

    If you remove the mound you remove some of those concerns, but it's up to you and how you want to use the area.

    Best of luck with whatever you decide. Perhaps you'll update us sometime when you've made progress?

  • Thank you, that's helpful. I have an almost unlimited supply of horse manure (family horses/ponies so I know exactly what went in it) which is handy. Removing some of the soil could be tricky or at least heavy work, since the garden is not accessible by vehicle, but definitely something to ponder on... I don't mind the mound itself and was thinking to edge it with logs or something to make a border, just to stop it spreading without us realising, but I guess removing some of the remains there would at least lower the contamination level if there's anything left behind.

    I will definitely let you know how I get on. 
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