Were the black speckles on my mint plants rust?


I had a mint plant that was spreading and I noticed that all of it seemed to have black speckles on it. I think it might be rust? So I pulled up what I could, bagged it and threw it away. Could it have been something else? Should I be concerned? 


Jonathan Foster, Home Horticulture Outreach Professional

Without seeing photos, it’s a bit tricky to diagnose. There is mint rust (often occurring when the growing conditions are wet), although the spots tend to be browner than black. It’s also possible that it was damage from the feeding of the four-lined plant bug, which does leave black speckles. Neither is a huge threat to a healthy patch of mint–which can be aggressive under the right circumstances and can actually turn into quite a weedy headache if it spreads. We often recommend planting mint in containers or in a bed surrounded with a barrier of edging to prevent it from getting out of hand.

Happy gardening.