Mint is a strong resilient plant that is quite able to look after itself providing you don’t over-water it. However, if you are growing mint regularly the chances are that at some stage your mint will be affected by the mint rust fungus.
You’ll be able to recognize the mint rust fungus (called Puccinia menthae by the scientific community) because your mint plant will look very unhealthy. On closer inspection you’ll find orange pustules on the stems and leaves. As the infection progresses the leaves turn brown and die.
What Causes It?
Mint is meant to be particularly susceptible to mint rust if it’s grown in the full sun, but in my experience you’re just as likely to get it if your mint is not in full sun. Infected plants will contaminate the soil and will carry the infection through the winter into the following year.
What to Do About Mint Rust in Growing Mint
Sadly, there isn’t a good chemical remedy for mint rust if you want to be able to use your mint after treatment. I haven’t yet come across an organic treatment, although I am still looking.
If you correctly diagnose that you have mint rust it’s important to act quickly to deal with it because the “spores” which develop with the disease drop onto the soil and will affect your mint in following year and could also infect other herbs such as majoram and savory.
Take the following steps:
Step 1: Cut off all the stems of the growing mint immediately the rust is noticed, and keep cutting them off during the growing season.
Step 2: During the winter make a small fire with straw over the top of the mint roots. This kills off the spores which carry the disease
Step 3: In the spring watch carefully for a repeat of the rust in your growing mint. If it returns repeat the procedure or dig the mint plant up and destroy it.
Growing Mint the Following Season
If you decide that you want to keep your mint plant and encourage it back to healthy life, quarantine it in its own pot and keep it well away from all your other herbs. Use the straw fire treatment as described above and watch carefully for signs of rust when the mint starts to grow the following season. Also use the straw fire treatment on the soil where your mint used to grow.
I thoroughly recommend always growing mint in a pot on top of your herb garden (if you’ve got one) or in its own pot on your patio. This will help to restrict root growth and enable you to deal quickly with infected plants. Use your pot just for mint. You can make it more interesting by having a number of varieties of mint in the same pot.
Finally, don’t despair if you get mint rust. It happens to all herb gardeners at least once during their herb growing lives!