Mint Rust? Or Spider Mites?

The mint transplants that I got for Dr. Kong are growing well, but I’ve noticed the leaves are getting these white and black spots. What is it?

I had put Golden Gate Gardening by Pam Pierce on hold at the library a few months ago, and I, just recently, finally got my hands on it. It’s a very informative book, and I definitely recommend it for any Bay Area gardeners. So, as soon as I noticed the spots on my peppermint, I read her section on Mint. Under Pests and Diseases, the only pest or disease she discusses is rust. She says, “Peppermint is subject to rust, which does not change the flavor and rarely kills the plant, but disfigures the leaves with rust-colored spots.” Could my problem be mint rust?

Mint rust is a fungus that causes orange, yellow and black spots on the leaves of mint. When I do a google image search, I get pictures that look more like this:

Image: gardening.which.co.uk

Hmmmm…. that doesn’t seem quite right. Darn. Golden Gate Gardening doesn’t seem to have the answers in this case, but I still stand by my recommendation.

Further googling, led me to this:

Image from: entomology.ca.uky.edu

This isn’t a mint plant, but the damage sure looks like what I’ve got. It’s spider mites. They live on the underside of the plant and suck the sap from the leaves leaving pale yellow spots. Spider mites are incredibly small – 1/50th of an inch – and yellow/orange in color. You usually need a magnifying glass to see them properly, although some sources say you should be able to see their webs with the naked eye.

I tried looking for the spider mites with a magnifying glass by shaking the leaves onto a white sheet of paper. There was one yellow-ish bug (I think) that fell onto the paper, but it flew off before I could get a good look at it with the magnifying glass.

The treatment for spider mites is insecticidal soap or neem oil. I’m a little uncomfortable spraying one of those things on my mint leaves, even though they’re “organic” or “natural.” I eat the mint leaves without washing them and the thought of eating insecticidal soap is kind of gross. An alternative treatment is predatory mites. These are beneficial insects that will eat the spider mites and then die off. I am so intrigued by this.

If you agree or disagree with my mint diagnosis, let me know. Also, if you’ve used predatory mites (or other predatory insects to control and insect pest problem) let me know.

Growing Mint For Tea

Mint grows like a weed. If you put it in the ground it will spread and take over. Once you have it, it will be hard to eradicate. You really need to keep it in a pot to prevent it from spreading. A nearby community garden made the mistake of planting mint in the ground.

So much mint!

But their mistake is my good fortune. I’ve been wanting to try to make my own mint tea, and since the only kind of gardening I’m doing at the moment is container gardening (not counting the community garden, of course), I thought now would be as good a time as ever to try to growing mint.

I pulled up a bit of the peppermint from the patch at the community garden, cut the roots/rhizomes into roughly 2 inch pieces and put them in a pot. I gave them a bit of water and that’s it.

Mint cuttings to plant

There are a million and one recipes for mint tea with fresh mint leaves: The Spruce Eats, Gourmande in the Kitchen, Martha Stewart, Champagne Tastes….

They all say pretty much the same thing:

  1. Get a bunch of fresh mint leaves
  2. Put them in a cup or teapot
  3. (Optional: Muddle the leaves)
  4. Add boiling water
  5. Let steep for 5-10 minutes

I followed those steps, and the results were….

Steps 2 and 3: Mint leaves muddled in a cup
Step 4: Add hot water
Step 5: Steeping for 5-10 minutes

…lackluster.

The tea was weak and bland. I left it steep for longer (30 minutes), which resulted in weak, bland, and lukewarm tea.

I left the concoction sit in the glass overnight, and when I checked on it the next morning, it was much darker in color and finally tasted like mint! I re-heated it and added a tiny bit more boiling water, and it was actually pretty good.

After steeping overnight, mint leaves (mostly) removed

It’s not quite the same as the mint tea bags you’d buy at a store. It has a slight…uh…earthy note. It takes a little getting used to, but after a few sips, it’s just as good as the store bought stuff.

If you like fresh mint tea, I think it would be best to brew up a pitcher of this tea once a week, and keep it in the fridge. Reheat a small cup-fulls as you like, or drink cold as an iced tea. I haven’t tried adding honey or sugar, but I imagine that would be fine.


Marie’s Recipe for Fresh Mint Tea

Serves: 1 (multiply recipe for more portions)

Time: 5 minutes (plus 8 hour steeping time)

  1. Get a bunch of mint leaves (maybe 10? 20?)
  2. Place them in a cup and “muddle” them by mashing them with a wooden spoon for a minute or two
  3. Add boiling water to the cup
  4. Let it sit for at least 8 hours, or longer if you’d like
  5. Strain out mint leaves
  6. Reheat and enjoy! (Or refrigerate until chilled and enjoy!)