What is causing the brown spots on my potted lemon balm plant? - Ask Extension
I have a lemon balm plant started from seed, transplanted into a large (at least 12") pot that I leave outside.
It's probably 5 months old and doing ...
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What is causing the brown spots on my potted lemon balm plant? #269925
Asked August 13, 2015, 3:16 PM EDT
I have a lemon balm plant started from seed, transplanted into a large (at least 12") pot that I leave outside.
It's probably 5 months old and doing well.
Closer to full sun but gets some shade.
Moderate occasional watering.
Completely organic/no fertilizers.
My concern is that, while it does grow very fast like a weed, most lower leaf pairs are brown on the edges of the leaves or have brown spots. The newest two pairs of leaves are always fine, but I'm wondering what the browning is.
Prince George's County Maryland
Expert Response
You may be seeing more than one problem.
Brown edges suggest a root issue, in other words, enough water is not getting up from the roots. (Or the plant is drowning, and roots are rotting.)
Lemon balm wants moist soil. Let the top 1/2-1" of soil dry between waterings, but if you put your finger in the soil and it is drying any farther down, then it needs to be watered more often. Watering intervals vary depending on air temperatures, but also how breezy it is, humidity, and cloud cover.
It also requires good drainage.
The bottom leaves may also just be old. Pull them off if they start to die.
The spotting could be a leaf spot disease, in which case you should also pull off those leaves. Here is a good webpage that addresses the leaf spot (page 14): http://www.herbsociety.org/factsheets/Lemon%20Balm%20Guide.pdf
ECN
Brown edges suggest a root issue, in other words, enough water is not getting up from the roots. (Or the plant is drowning, and roots are rotting.)
Lemon balm wants moist soil. Let the top 1/2-1" of soil dry between waterings, but if you put your finger in the soil and it is drying any farther down, then it needs to be watered more often. Watering intervals vary depending on air temperatures, but also how breezy it is, humidity, and cloud cover.
It also requires good drainage.
The bottom leaves may also just be old. Pull them off if they start to die.
The spotting could be a leaf spot disease, in which case you should also pull off those leaves. Here is a good webpage that addresses the leaf spot (page 14): http://www.herbsociety.org/factsheets/Lemon%20Balm%20Guide.pdf
ECN
