Mojito mint, garden tour and geranium rust

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June 12, 2013
By: Meleah Maynard
An example of geranium rust.
Meleah Maynard

Let’s start with cocktails, shall we? In my last column I mentioned that I was having a hard time finding the mojito mint Amy Stewart referred to in her latest book, “The Drunken Botanist: The Plants That Create the World’s Great Drinks.” If you’re going to make mojitos, Stewart wrote, nothing beats mojito mint, a specific type of spearmint out of Cuba — the mojito capital of the world.

Having heard most garden centers don’t carry it, I looked online for retailers and was flummoxed to find that many places won’t ship mojito mint to our state. No matter. With the help of some of my fellow master gardeners, I’ve learned that it is for sale at Gertens and Linders. Bachman’s also carries it but it’s part of a larger arrangement in a large(ish) pot. If you can’t find it, Kentucky Colonel spearmint is apparently a very closer runner-up. Like most mints, it’s best to plant these spearmints in pots to keep them from taking over your garden. Check out Stewart’s drink recipes here: drunkenbotanist.com.

Garden tour in Southwest 

It’s garden tour season again and this year, the Hennepin County Master Gardener Learning Garden Tour is right here in Southwest on Saturday, July 13. Six master gardener’s landscapes will be featured on the tour, including a Japanese garden complete with its own teahouse, a peaceful Feng Shui garden, a variety of rain gardens and more.

Learn more about the tour and purchase advance tickets for $15 here: hennepinmastergardeners.org/events/hcmg-learning-garden-tour/. Or you can buy tickets the day of the tour for $20 at any of the gardens, which will be listed on the website above the day of the tour. Master gardeners will be on hand to answer your gardening questions, and there will be lots of educational demonstrations too.

Geranium rust

It just wouldn’t be summer (even though it really hardly is) without all sorts of funky diseases and pests plaguing our plants, right? I’ve got a few things rampaging through my gardens at this very moment, so I figure you might be dealing with some of the same problems too. First up: geranium rust. You know you’ve got geranium rust when the leaves of your lovely geraniums are dotted with yellow splotches that eventually get a brown splotch in the middle and things get worse from there.

The disease is caused by the fungus Puccinia perlargonii-zonalis, and it thrives in the kind of wet, cool weather we’ve had in abundance this season. Annual geraniums are more likely to get the disease than perennial geraniums, but there are exceptions to every rule. My perennial bigroot geranium (Geranium macrorrhizum) seems to be immune to the problem, for example, but all of my perennial cranesbill geranium are afflicted.

One of the best ways to avoid this problem is to inspect plants carefully for the disease before you buy them. This isn’t always useful because plants can have rust for a couple of weeks before showing symptoms, but it’s still a good thing to do. Even if you find rust spots on your plants, you may be able to stop the disease’s spread by picking off affected leaves and destroying them right away.

If it’s too late and your plants are all splotchy like mine are, the most commonly followed paths are to either rip the geraniums out or try treating them with a fungicide specifically for rust. I don’t want to use a fungicide because it might harm beneficial insects, and I’m not too keen on ripping out a bunch of my plants either. So I’ve cut them all down to the ground and thrown away all of the leaves and stems, hoping to stop the spread of spores. If the new growth has rust, I’ll get a shovel and say goodbye.

Why didn’t I add the plants I cut down to my compost bin? you ask. Good question. That’s because compost needs to be 140 degrees F to kill most bacteria and fungi and mine doesn’t get nearly that hot as I’m kind of a lazy composter that lets things break down when they break down. If you do a better job of managing your compost to keep it hot, you can have the pleasure of tossing those sick geraniums on the pile. Just don’t let your bins get about 160 degrees F because then you’ll start killing the good stuff that you need for healthy compost and soil.

If you’re wondering what in tarnation is wrong with one of your plants, check out the University of Minnesota Extension’s handy “What’s Wrong With My Plant” tool: extension.umn.edu/gardeninfo/diagnostics/ and then make yourself a nice, cold mojito.

Get more gardening tips at Meleah’s blog: everydaygardener.com