Do your echinacea (coneflowers) look like mutant, green monsters from an alien universe? Mine do. And that’s because a disease called aster yellows is running rampant in Minnesota this year. The disease is caused by a phytoplasma, a microscopic bacteria-like organism that makes its home in the vascular system of plants.
Not all plants can become infected with aster yellows, but many annuals, perennials, vegetables and weeds are affected by it, including asters, carrots, chrysanthemums, coreopsis, cosmos, daisies, dandelion, marigolds, onions, petunias, potatoes, thistle and tomatoes. Aster yellows isn’t a new disease. It’s just worse this year than it normally is for reasons experts are still pondering. Hot weather seems to have something to do with it.
Aster leafhoppers are the reason why the disease travels through gardens so quickly. They transmit the disease from plant to plant when they feed on infected plants and suck up sap that contains the phytoplasma. After a short incubation period in their tiny bug bodies (the leafhoppers are not harmed), the microorganisms multiply and the insects spread the disease further as they feed.
The symptoms of aster yellows vary from plant to plant. But most of the time you’ll notice that infected plants look stunted and distorted in weird ways. Foliage can be yellow and flowers often look yellow or a spooky shade of green. Seeds and fruit don’t develop. You might also see spindly stems and flower stalks. It’s not a pretty sight.
The biggest bummer, though, is that once a plant has aster yellows it can’t be cured. You’ve got to rip the whole plant out and throw it away. I know, I know. I don’t do that either. I just cut off the infected part of my coneflowers and let the rest of the plant that looks good stay. But that is a bad idea. Yes, I get to enjoy the relatively normal-looking parts of my alien, mutant coneflowers. But by allowing those plants to stay in the garden, I’m ensuring that aster leafhoppers will continue to spread the disease to other susceptible plants in my yard and my neighbors’ yards.
It’s really the same tough reality crew members on spaceships in sci-fi films often face. You remember the plot. They all know that their friend was infected by some horrible monster creature thing down on the planet they just visited without wearing proper protective gear (what’s up with that?). And they all know it’s only a matter of time before a baby monster creature thing bursts out of their friend’s chest and tries to infect them all. But, hey, for the moment the friend seems mostly fine, so why not let the poor sot live, right? We know how that story ends.
So let’s all vow to rip out plants infected with aster yellows—at least by the end of the season when we cut down plants for fall. It’s fine to throw these infected plants in the compost because the phytoplasma dies when the plant dies. Not all plant diseases work that way. Unfortunately, this harsh step won’t guarantee that aster yellows won’t come back again next year because infected leafhoppers are likely to still be around or you could inadvertently bring an infected plant home from the garden center. I think I’m finally going to give up on coneflowers all together. I like them, but I’m tired of knowing there’s a mutant, green monster lurking behind those pretty purple flowers.
Note: This post ran this week as my Everyday Gardener column in Minneapolis’ Southwest Journal.
In the summer, there’s always some amount of critter chirping going on in the yard after dark. But this year those chirps and trills are so boisterous and loud, you’d think we were in the woods rather than the city.
Others have noticed the change, too. And though we don’t understand what’s responsible for turning up the volume on the beautiful nighttime chorus this year, some master gardeners I know did figure out what’s probably doing the bulk of the chirping—tree crickets. In particular, snowy tree crickets (Oecanthus fultoni), which live in trees but like to roam the garden in search of things like aphids to eat. Thanks, little guys!
Not surprisingly, there are some great videos out there showing these critters doing their thing. Is it just me, or do you agree that it’s simultaneously enchanting and weird to see one of summer’s mysteries so nakedly exposed? Oh, and here’s my disclaimer: I am not an entomologist, so if these crickets are not correctly identified by the video’s poster, I apologize in advance.
Go here to see a male snowy tree cricket showing off for the ladies.
Click here to see a four-spotted tree cricket (Ocecanthus quadripunctatus) in action.
And here’s another four-spotted tree cricket singing.
One last interesting tidbit; snowy tree crickets are often referred to as “nature’s thermometer” because the rate of their chirping is related to the temperature. Opinions on the best formula to use to translate their chirping into the correct temperature vary, but the most commonly suggested method is to count the number of chirps in 13 seconds, and then add 40 to that number to get the temperature in degrees Fahrenheit.
Show me your garden and I shall tell you what you are.
— Alfred Austin
I don’t know enough about the English poet Alfred Austin to understand why he thought he could divine who, or more precisely, “what”, someone was simply by looking at their garden. But he makes an interesting point. Having toured many more gardens than I usually do this summer, I’ve really been struck by the vast differences in the look and feel of people’s yards.
Modern straight lines vs. curving cottage beds, shady oases vs. sun-drenched plots for edibles and brightly colored perennials, cherubs and ornate statuary vs. gnomes and silly flamingos. And probably not surprisingly, a near tie between the number of gardeners who like plant tags and the ability to see the soil between each plant and those who would never consider plant tags and prefer a more wild, overlapping look.
What would Austin make of this? “What” are these people? Does orderly equal neatnik, control freak or professional organizer while wild signifies some kind of messy, disheveled, devil-may-care personality? Maybe. But that seems too simple since, once you get to know most people, they often turn out to be much more complicated than they first appeared. He must have meant something more. Might we consider how each gardener’s parents and grandparents gardened? Where they grew up? Whether they need to grow food to put food on the table?Read More»
No one will ever make a reality show about gardeners. We tend to be sweaty, disheveled and a bit dirty for starters. Our shoes are functional. We wear big, floppy hats. We’re pretty keen on shorts, pants and sometimes vests with lots of handy pockets. And we love, love to gather together and talk about plants, plant problems and bugs.
“Does milk really help stop powdery mildew?” “Is aster yellows caused by a virus or a phytoplasma?” “Why that is the largest scale bug I’ve ever seen! And you removed it using a power washer, amazing!”
Yeah, we couldn’t even sell the Gardeners Gone Wild topless version of this stuff.
But we could use your help with a current topic that’s come up this year. Some gardeners around Minnesota have reported seeing Japanese beetles feeding on geraniums and then acting, well, drunk or stoned or something. Jeff Hahn, an entomologist with the University of Minnesota Extension Service says it’s really unusual for Japanese beetles to feed on geraniums because geraniums contain a toxin that “intoxicates” the beetles to the point where they can be paralyzed for hours. (Read more of Jeff’s interesting updates on garden pests here.)
Apparently, this experience isn’t half bad because once they recover the Japanese beetles go right back for more. So, if you have Japanese beetles getting blackout drunk on your geraniums, Jeff and others with Extension would love to see some photos. Please email your photos to me, or send me a link to Flickr or wherever you post photos, and I’ll forward them on. Let me know what state you live in, and how long you’ve been seeing Japanese beetles on your geraniums, too.
Oh, and one more thing. Several master gardeners have been wondering whether it would be a good idea to interplant geraniums with roses, grapes and other plants Japanese beetles love in hopes that they would flock to the geraniums and leave other plants alone. Unfortunately, Jeff Hahn says that research has shown that the strategy doesn’t work. In fact, even more beetles show up than before. The upshot? You may not want to plant a geranium beetle bar in your garden unless you want them to party at your house.
Okay, just kidding. We’d probably keel over if we had to get the garden in shape for a tour every year. But it was a really fun day and if someone asked, we’d probably offer up our yard again for a tour in the future. Even though it was in the 90s with extremely high humidity, the 9-hour day went by fast and we honestly could have gone on yacking with visitors for at least another hour or two after the 4 p.m. closing time.
The numbers have been crunched and it looks like we had 367 people touring the 11 gardens on display—that’s the biggest year yet for the annual Hennepin County Master Gardener Learning Garden Tour. Our garden is small and the paths are narrow, so we were worried that visitors might feel cramped and rushed in a way that would keep them from experiencing the garden as it’s meant to be experienced.
Luckily, people trickled in throughout the day and meandered down the paths looking at everything. Everyone was smiling and happy and had a lot of questions. It’s mostly true that mean people don’t garden, and this day was a testament to that. Love fest would be a good way to describe the day, really, and who doesn’t want more love?Read More»