Experiment Update

I don't have indisputable results yet, let me be clear about that up front. But I am seeing some differences between my asters that underwent the milk solution/dormant oil experiment (full details in this link). Click on any photo for a closer look.


Here is the smooth blue aster (Symphyotrichum laevis) sprayed with the dormant oil solution. Unfortunately, it still has these brown spots that are spreading to newer leaves. However, this doesn't appear to be powdery mildew, so I guess that's a positive, but this plant is definitely struggling. It's also still a snack for the local rabbit, which is apparently enjoying the soapy vinaigrette.


Here is the aster sprayed with the milk solution. The white cast is dried milk, not mildew. So far the discolorations on the lowers leaves haven't spread to more foliage.

Since neither of these plants are dealing with an out-and-out mildew infection, it's impossible for me to say definitively whether milk or the dormant oil is the better fungicide. But the milk solution does seem to be keeping the plant healthier than the oil, at this point. I must admit, however, that the control aster is doing the best of all:


Results are even less clear with the monardas. Here's one:


And the other:


Can you tell a difference? I couldn't either! (For the record the first one had the milk and the second had the dormant oil.) Neither has powdery mildew or any other noticeable fungal infection, so that's great! I guess both solutions are working equally in that regard. But both of these monardas are being chewed relentlessly by insects, and neither solution is helping that problem. I suppose that's why "dormant oil" is meant to be applied when a plant is dormant!

Here's a look at one of the control monardas. As you can see, it looks just like the others.


I will probably apply another round of my solutions this week because we've had more cool rainy weather (what a shock!). I'll keep you posted on more developments, and I hope everyone has a great weekend!

A Garden Experiment

Aptly observed by Carol at May Dreams Gardens, certain things are missing so far this summer. In my garden, powdery mildew is conspicuous in its absence. In the past it has descended on my garden early in the season, around June (when it murdered the monardas), and later, in August (last year in the aster attack).

But I'm not letting down my guard. We had months of soggy weather capped by deluges a couple weeks ago; now it hasn't rained in over a week (10 days? Almost two weeks? I lost track). I'm concerned that these adverse conditions could give the dreaded mildew an opportunity to maim the confused and struggling plants. So on the advice of some extremely helpful readers/bloggers, I am applying the proverbial ounce of prevention.

I have complained about my battles with powdery mildew in the past, and based on the comments from that post I have devised a little experiment with my new monardas (M. fistulosa) and smooth blue asters (Symphyotrichum laevis).

Garden Girl did some research and discovered that a milk/water mixture is recommended for mildew problems. I took a one quart spray bottle and made a 1:3 mixture of milk and water. I used 2% milk. Here's a look at a milk-mixture-sprayed aster.

(Got milk?)

I also sprayed one of the monardas with this mixture.

Gail suggested a recipe she learned courtesy of P. Allen Smith. I whipped it together and sprayed it on a second aster and a second monarda.

(This aster has ominous brown spots, now coated with dormant oil mix. My apologies for the harsh afternoon lighting.)

In one gallon of water, I mixed 1 heaping tablespoon of baking soda, one tablespoon of vegetable oil and one teaspoon of dish soap.

(Here is the monarda with an oil-illuminated spider web in the bottom left.)

Of course, any experiment must have a control, so I left my third smooth blue aster un-sprayed, as well as my other two monardas. What will I learn? Well, it could be a lot or nothing at all. Maybe one mixture will prove effective and the plants sprayed with the other will succumb to the mildew. Maybe both sprays will help and the controls will go down. Maybe every plant will survive unscathed because powdery mildew never gets near my garden this year (yeah, right). We'll have to see what happens!

(Milky monarda with spider web. Both mixtures look similar when sprayed, as the soap resembles the watered-down milk.)

On a side note, the baking soda-oil-soap mix was recommended to prevent insect damage, which is also a problem here. The asters are being eaten by a rabbit, but the monardas are suffering from some insect pest, I haven't figured out exactly what (likely earwigs since japanese beetles have been nowhere to be found). So I will also be watching to see if this "dormant oil" application cuts down on the bug damage!

And just for kicks, here's a gratuitous picture of my astilbe, which is blooming for the first time in two years! It's proof that for every challenge in the garden, there is another reward waiting!

Scourges of Summer

I am grateful for the recent rains here in Chicagoland because they have kept me from having to water the garden, and my new plants, particularly those in the rain garden itself, are benefiting from the frequent moisture. However, this has been a soggier spring than usual, and such conditions portend the arrival of two of the worst summertime scourges--powdery mildew and earwigs.

Both develop and thrive in moist, humid, hot conditions. Powdery mildew absolutely decimated the bee balm (Monarda didyma) I tried to grow a few years ago. I was so traumatized by their hideous demise that I have just this year planted some wild bergamot (M. fistulosa) in the hope that the native monarda species will be more mildew-resistant. The current moisture conditions are challenging this foray back into bee balm.


(Can the wild bergamot outwit the mildew?? Odds aren't good with them laying prostrate on the ground...)

Last year the mildew attacked my smooth blue asters (A. laevis), so already my confidence in the natives' ability to avoid this blight is shaken. I removed some suspicious-looking leaves from the asters last week and am closely monitoring the foliage now. The leaves were browned with some black spots--not the telltale white gunk of powdery mildew--but I'm hypersensitive nonetheless.


(Will this aster be a repeat victim?)

As for the second issue, earwigs, I don't know precisely how much damage these disgusting invaders do to my plants, but I highly doubt they contribute anything positive to our little ecosystem here. In the past they have set up shop in my containers when the potting soil remains moist. As a result, there have been times when I stuck my finger in the pots to check the moisture level and swarms of earwigs crawled out. Needless to say, my screaming and flailing most certainly qualified for some "goofy gardener" behavior, a la Carol/May Dreams Garden.

Let me qualify something here--I'm not anti-insect. I grow plants to actively encourage butterflies, bees, and dragonflies to visit my garden (yes, pretty non-scary bugs, I know). I don't disturb the spiders because I know they're eating other bugs. When I saw the guy below, I didn't run, I took a picture. But until someone provides proof of any benefit from earwigs, I will continue to loathe them and smush them on sight.


(What is this insect, in repose on a leaf of pale purple coneflower? Click the picture for a close-up.)

Regardless of my particular prejudices, our rainy, humid weather encourages various garden pests, so if you live in northern Illinois, be on the look-out. I've tried spraying a baking-soda-dish-soap-water mix on the mildew-covered asters but to no avail. I still won't resort to chemicals. I've tried to follow the "ounce of prevention" maxim by amending the soil to make the plants themselves healthier, and I'll still be removing suspect foliage. Are there other suggestions out there for dealing with powdery mildew? How do you cope with this or other climate-related scourges?