Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Why Are My Mint Leaves Turning Brown?

Hello! So I got anxious for spring the other day and bought mint plant at Sprouts' "3 for $10" sale. So far the other two plants I bought (german camomile and oregano) are doing fine, but something isn't right with my mint. It looks fine on the outside and has some new growth at the top, but when you look closer, some of the inner leaves appear to be rotting and are falling off! (Pictures attached)

All three plants are sitting in an Eastern facing window together where they get bright light in the mornings and decent light the rest of the day (at least until they can go out during the summer time). I've read that mint's soil needs to be kept moist, so I've been watering it every 2-3 days. I also mist all of my house plants once or twice a week for humidity.

Is it rotting due to too much water? If so, how much/how often should I be watering this plant? Should I not be misting it?

I am also concerned that it is a fungal disease or something that might spread to the other herbs in the window. Do I need to get rid of the plant so that it doesn't infect my healthy plants?

As always, thank you all a bunch :()
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imafan26
Mod
Posts: 13962
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Mint will do that when it gets too much water or for whatever reason the pot does not drain well. It is growing lanky and either it was crowded among other plants or in the shade. The top looks good. I would pick off the bad leaves. It looks like it was re-potted recently. you can always take cuttings or layer the mint to make new ones.

Mint is an agressive plant. When the pot looks 'really full and nice' is usually the time to check the roots. if they are winding around the rootball, it is time to divide the plant otherwise it will choke itself.

My mint is grown pretty much in full sun so it is full but more prostrate, it really doesn't do much vertical growth.

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Thanks for the advice. I picked off the bad leaves and noticed that some roots are poking out of the drainage holes in the bottom, so I assume this means it needs to be divided. Do I just get another pot of similar size and split the plant/rootball in half between the pots? Is this preferable to just giving the whole plant a nice big pot to fill up? And gosh what do I do when I have more pots of mint than I have windows if I have to keep dividing them up like this? lol :) Thanks for the advice, I guess I didn't really know that much about mint!

imafan26
Mod
Posts: 13962
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

You can either pot it up to a bigger pot or just cut it into two or three pieces. I sell some of the mint and some I give away. When there is more than I want anymore, I just put it in the green waste. I don't keep more than three pots as backup. I put mine in 10 inch hanging baskets and hang them in the tree so they don't touch the ground.

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

I bet hanging pots smells nices when the wind blows, I'll have to give that a try.

Flowers
Senior Member
Posts: 116
Joined: Thu Jan 08, 2015 2:30 pm
Location: Fort Collins, CO, USA Zone 5b, sometimes 6

Thanks for all the advice! I repotted and watered less, and all the rot is gone.

pepperhead212
Super Green Thumb
Posts: 2852
Joined: Wed Oct 15, 2014 1:52 pm
Location: Woodbury NJ Zone 7a/7b

That definitely looks like a drainage problem, not a fungus, as there are a lot of nice leaves there. I get a disease, sort of like a rust, on my mint early every season, and it is on EVERY leaf! They get sort of speckled with brown, but it is gone by mid June, usually. Last season I sprayed a bunch of Actinovate on it, every couple weeks, and it pretty much prevented it, but I don't know if it was a year it wasn't going to show up, or if it truly prevented it, as I didn't leave any test areas!

Mint is another thing I get huge amounts of, as I have a flowerbed with just mint (the only place to plant it, as it is surrounded by concrete!). I cut large amounts of it and take it to work, for those who want it, like I do the rosemary.



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