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Hello all,

I have a few pots in the garden which are turning green on the outside. There's a thin green slime coating the exterior of the pot. The plants inside the pots are healthy so am at a loss as to what is happening. Can anyone help?




It's a perfectly normal process of weathering.  If you don't like it you can scrub it off.  There are also products on sale in GCs and DIYs for removing algae from paths that can just as well be used on pots and garden ornaments.


It's almost certainly algae and will be more likely to appear on pots which are in shady areas and never dry out.  I actually quite like the effect as it suits my cottage-style garden but I can understand it looking unsightly in other garden styles.

It can be cleaned off by removing the plant from the pot and scrubbing with soapy water.  Soaking them in a diluted bleach solution afterwards will stop it coming back so quickly, but it's almost inevitable with unglazed clay pots.

If you use a jet-spray on a patio, it can also be used to clean pots and containers - but  as Bob says, most containers look better with a nice bit of weathering; even better if the algae develops into moss or lichen!


I like them left as well, they turned a bit black in the summer, but they look better than that just bought look. 

If you clean them now they wil be green by the Spring again.



Thanks all! Seems harmless enough. Will leave it on through the next 2 seasons and see how they look come the summer.

Highland Jeannie

In a raffle I won a large unglazed clay pot of pelargoniums.  They are extremely thirsty & their pot has gone green in the lower half despite being indoors on a sunless windowsill.  I agree it's not a bad look for outside & having read your replies to Gareth, have decided that the "rustic" look inside isn't too bad either!


I much prefer the 'mature' look to the pristine style

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