When it became a bit warmer again I put my mint plant outside after it stayed inside for the winter. However, after I came back from a short vacation, almost all leaves turned black. I don't know what is wrong...

Also there are white grain-like, chalky thingies in the soil. They are not stones, if I take one and squeeze them they pulverise and it is like chalk. Can this hurt? What is it?

Can it be that the transition from inside (~20˚C) to outside (~8˚C at the time) was too sudden and it died of cold? What could I do now to save it?

The mint plant from up top

Little white chalk-like grains

The pot the mint is in -- no drainage

1 Answer 1


Yes, transition shock to a degree, it should have been hardened off before being left out all the time, not only to acclimatize to colder, variable temperatures after being indoors for some time, but also to get used to direct sunlight on its leaves.

It is not, however, dead - turn it out of its pot, split or select live parts from what's there, removing any dead pieces, and repot into two separate pots in fresh potting compost. Or bin what's dead or unhealthy and pot the rest. Mint puts out long runners below ground when planted in the garden, and then pops up a couple of feet away and starts growing - it can't do that in a pot, so the centre tends to die back and, if left in the pot, the whole plant gives up and stops growing. The way to get round that is to pot up fresh runners and half the original each year, or every other year.

As for the little balls which pulverize when you squeeze them, they'll be spent feed granules present in the compost, nothing to worry about.

  • 2
    I believe the little balls are actually perilite, added to prevent the soil from getting compacted, rather than spent feed granules. Otherwise, a perfect answer!
    – michelle
    May 11, 2015 at 13:34
  • 1
    @michelle - yea, could be perlite or vermiculite, but whatever, nowt to worry about.
    – Bamboo
    May 11, 2015 at 13:36
  • Agreed, Bamboo!
    – michelle
    May 11, 2015 at 22:04
  • Thank you so much for taking the time to answer my questions! I'm going to try what you said and see if it has any effect. I'm learning every day here :)
    – Coen
    May 18, 2015 at 9:06

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