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Hi - just recently had the patio removed and discovered underneath it are wall foundations of an old building, which I think might have been a coal shed at some point because my beautiful soil has lots of tiny bits of coal and coal dust in it. I was intending to grow flowers, fruit tree, raspberries and/or runner beans because it's a lovely sunny spot and my normal soil is fabulous but not sure if it's now contaminated. What shall I do? If I dig it all out and replace with new top soil, to what depth should I dig? Any ideas, anyone? Also, if i have to buy new top soil, are there different sorts and which one should I get. Many thanks.


Coal is not really contamination; it came out of the earth, it is just charcoal in another form.  Add plenty of compost/humus to the soil, and off you go!

I would suggest either digging it out and replacing it with clean top soil or putting a raised bed. Even though you don't mention that there is coal cinders there, it is always a possibility. Coal contain many toxic elements and heavy metals, therefore to place fruit trees that are going to absorb these elements and find their way into your diet is a bad thing.

I'm no gardener, having only been on this site for 2 days, but I am studying for a science degree in geology, so know a little about the possible contaminations that can occur.

HTH's. I would be interested to see what a gardeners perspective is on this matter.

ha my first two responses have totally opposite views! (but thank you for being so quick)

wonder what anyone else has to say?! 

havent seen any cinders yet. just looks like black coal bits but also have found some pinky orange clay, which is weird because my soil type is river basin valley stuff, ie very dark and no clay at all. 


My Grandad's garden was heavy clay (so much so I took some into school and my pottery teacher fired it as an experiment), and that had tiny bits of coal in it.  Have you tried digging down to find out how deep it goes?  Obviously if it's only a couple of inches, then I'd move it, but if the clay goes down more than a foot, it will be one helluva job to shift it.

Personally, I'd see how far down it goes before deciding on anything.  If you get fruit trees, you can keep them in pots for a few years, so if there's lots of contamination, shift it in stages, but still have your fruit trees, and hopefully by the time they need planting in deep soil, you'll have fixed your problem.

My Grandad planted some fruit & veg in his garden (after adding LOTS of sand and manure), and was in his 70's when he died, so if there are tiny bits of coal in a heavy clay soil, then I can't see it being a problem, as it didn't affect him (mind you the smoking and drinking he did didn't seem to affect him, and I wouldn't advise doing either)!  I don't claim to be a scientist, but I think most of the nasty stuff in coal is released when the coal is burnt (heavy metals and sulphur), so if it's not burnt I don't think you'd have a problem.


hi MMP - i'm waiting till the builders have gone, then I'll do as you say and dig deep just to really see what's what. thanks for advice.

Ignore my original post for the time being. I was a bit hasty in my response, and as there is conflicting opinions, I feel I should do a bit of research in the matter for you before I comment further. As I said, training as a geologist, not an environmental scientist or biologist, so will have to look into it before I am confident in backing my original post.

As an older gardener and mother of 4 I'd just like to point out that many pregnant women eat coal and many children also.  To my certain knowledge no one has yet died, been poisoned or suffered internal problems.  Dig the soil out if you want, or leave it and as already advised add plenty of organic matter and plant what ever you choose.  Happy gardening

After doing a bit of digging (no pun intended), it is probably ok to plant on the space if it is just coal/dust. But as said before, if there is any sign of coal ash, probably not a good idea. Although US environmental studies shows that small amounts of ash are beneficial to crops with little uptake of contaminants. But this depends on the crop planted, leafy plants, such as lettuce and spinach, show high concentrations of contaminants within their structure, whilst more fleshy plants like peas, beans and FRUITS tend to show small uptake but with high concentrations on the fruits surface that can be easily washed off.

Quite interesting reading about this, and may be a possible research proposal as there is not much research on the implications of small scale contamination and the uptake of contaminants by the biosphere. Most research is done on the large scale contamination caused from power plants etc.

Every inch of our garden contains bits of coal and in places it is almost pure cinders. The Veg gardens have the least coal and no cinders, and we have had no problems so fat in 20 years of eating.

Be glad your garden does not have our major contaminants.......hundreds of batteries from the old accumulator types with lead plates to modern torch batteries. We had to put the Veg  areas where there was the least number of these things.

I think the clay residue is possibly from the coal fires.

wow! what a brilliant lot you are!  i really appreciate all the helpful advice. 

richardsdrr - I'm impressed with all your research and look forward to hearing anything exciting 

berghill - I'm sorry about your batteries 

yvonne1 - yum!  I'll get stuck in, then!


I recently visited a garden in Charleroi which has a lot of coal slack in its soil and the bottom end is almost completely coal slack and yet, with added compost, the owner has made a beautiful garden open under the Belgian Open Gardens scheme and has a prodcutive fruit and veg plot.

I suggest you prepare the soil in the usual way for new or revamped beds - dig it over well to open it up and than add plenty of garden compost and well rotted manure to improve it before planting.   Mulch with compost in subsequent years and Bob's your uncle.

It may seem odd that coal made from trees and other organic matter can contain heavy metals such as lead, mercury and (radioactive) uranium and other pollutants but it does. The contaminants come from the normal geological erosion of rocks and are washed into the swamps where coal is formed. These are mainly concentrated in the boundary seams of coal but you have no way of telling where in the seam the coal came from. The heavy metals can leach out of the coal to pollute water courses. This largely a problem for power stations where they store millions of tons of the stuff.

If the layer isn't too thick I would dig it out first especially if planting fruit and veg.

The pinky bits might be brick debris from the previous demolition of the coal shed.


thanks obelixx and steephill. taking everything into consideration i think i'm going to play safe and dig out as much as I can and then fill with new top soil and loads of compost. then i'll plant something ... not sure what ... anyone know something i can grow that actually feeds the soil AND looks vaguely like I'm growing it on purpose?

It's the right time of year for one of the 'green manure' type crops like clover (although there are better ones out there than clover).  It might not LOOK like you're growing it on purpose, but it's good at replacing things like the nitrogen in the soil, and if anyone asks, you can tell them that you ARE growing it on purpose!  That way you won't need as much compost in the mix.  Just don't plant root veg on it next year (apparently the roots of things like carrots and turnips and the like grow downwards in search of nutrients, and if you plant them in newly-manured beds, they won't be very good).  My next-door neighbour is lucky enough to have an allotment, and he's full of useful advice about veg planting!


Thanks MMP - I was hoping you wouldn't mention clover! Oh well! Thanks for all your great advice. Clover it is.

Clover is only one of the green manures. You could also consider field beans, rye grass, alfalfa...would suggest you google green manures, and find which one would best suit your needs. I personally think the clover looks pretty!

It doesn't have to be clover - just checked my Which gardening mag, and the best green manure in their trials was phacelia.  ot sure where to get it, you could always try amazon & fleabay, or someone else may know where to get it.  It's mentioned as a 'crop' to grow now, if you've not got anything ready for winter veg beds.  It looks prettier than clover, and if it's come out well in their trials, that's the one I'd be going for.

thanks figrat and mmp - i just googled phacelia and it looks quite pretty, so i bought 25,000 seeds for £3.49 (including delivery) from Amazon - wonder if 25,000 was a bit much, but I suppose I could plant it over my entire garden and do the OK soil a favour. thanks again for everyone's help. 

I use phacelia, but must point out that it is frost tender. Have had a couple overwinter in sheltered little niches. Field beans, clover and rye grass are more reliable winter toughies.