Might be too much water, as thats what causes yellowing leaves. Purple color may be just a natural state if its in strong sunlight. Judging of the small yellow leaf on the left side of the bottom photo, any watering should be done at the soil level and not applied to leaves. Phosphorous usually has no efect on color, is its mostly for roots (runners!) and blossoms. Because its in a pot, a fertilizer can be useful. Something with a slightly higher nitrogen level. Additionally, as mentioned in another recent thread, iron might be low, so use a small dose of Ironite liquid as a suppliment to fertilizer. If more leaves tend to get yellow and spotty, it could be spider mites. In the upper photo, that single leaf at the bottom may just be getting old, and will soon drop off. Sometimes seasons will prompt plants to send off runners, so that might also be normal for now.

I'm glad to hear that it's normal. I thought it was a fertilizer issue because I have another mint growing hydroponically in a bucket of clay pellets right next to the window box, and those leaves are a much paler (though still healthy looking) green.

I grow the mint on the northeast side of the house where it gets some sun in the morning but is shaded in the afternoon. Last year, I think the full sunlight last summer was too strong for it, and the leaves were going brown and crispy on the edges. It seems happier in partial shade. I don't typically pour water on the leaves, but it has been out in the rain a bit lately.

I'll try using a little more nitrogen fertilizer. Is it easy to over-fertilize mint?

I find that my mint goes a bit purple with the cold - a bit like my hands and feet! I don't worry about it at all. As long as the new growth is healthy, everything's just fine. I also live in the subtropics, where temperatures are mild, but perhaps you had a bit of a cold snap overnight recently?

Don't overdo the fertiliser. It's as easy to kill any plant with too much fertiliser as it is to ignore it completely. A handful of compost or fresh potting mix to top up soil levels in the pot, or a repotting in fresh potting mix, is all you really need to do. If you must fertilise, use a general-purpose, slow-release one according to manufacturer's instructions.

You can overwater mint, but it isn't an easy thing to do if it's in a pot with adequate drainage holes. A bit of subtropical rain isn't going to do it any harm at all - yep, I'm in the subtropics, too. I have only ever lost one plant due to overhead watering/rain - and that was Lamb's Ears, whose leaves absorb water.

We had a pretty bad winter, by subtropical standards. I think they said it was the coldest winter in 40 years. All the houses here are uninsulated concrete boxes with no central heating, so it wasn't much fun for the humans either.

All my outdoor thyme is purple now too.

Hi there,

I know this is really old but it's exactly what is happening to my mint and I'm pretty worried about it. Was your mint plant ok in the end or did you have to re-pot it or fertilze it?

I have found the new leaves that are in the sunlight are going a little purple as well but maybe they are just cold?

I am curious too as to how things went. I recently purchased and then repotted a mint plant. I have kept it watered and I place it in front of the window most days. I noticed I have three purple stems, but mine seemed to have started not as old growth that may be dying off, but almost like suckers that have tiny leaves, the stalks are purple, they are growing out of the pot and downward and they are tougher stalks than the rest of the plant, not the dainty stuff that makes up the rest of the plant.

Hi, reference mint plants. I bought a peppermint Saturday but didnt get a chance to pot it till Sunday. However prior to potting i noticed the tips of the leaves were brown (which wasn't so when i bought it) and it's been getting progressively worse. I'm from the Caribbean and this is my 3rd go at it. Will upload pics to support text. Any assistance will be appreciated.

The soil looks very squidgy. It should be moist, but not wet.

hi can you still eat the purple mint leaves? thanks