Flowering dogwoods

What has the weather been like for the past 2 - 3 weeks?

Rainy and cool the first half of last week (highs in the upper 60's Fahrenheit); mixed clouds and sun since then. Overnight lows have been in the 50s for the most part.

Sorry I didn't say hello earlier, lab rat.
Hello, and good to meet you!

Have you looked at the underside of the leaves - anything moving around?

I'm just asking some general diagnostic questions - we should really grab SealPoet and ask him to have his wife come take a look here - she is studying to become a master gardener I believe. I'll look at this again once I get home. I don't keep gardening references at work :wink:

Hi, ehBeth!
I've checked for "critters". There are a couple of little spiders with webs between branches, but nothing else visible. Earlier in the summer, we had a lot of green silkworms--they were everywhere in the yard, but 3 or 4 made their home in the larger of the two dogwood saplings. The aforementioned 3-in-1 spray seemed to get rid of them, though.

Hi - this is Mrs SP. I am really studying to be a landscape designer, not a master gardener. But, will try to help.

Dogwoods are often susceptible to anthracnose. According to a site from Cornell: "The earliest sign of trouble, however, is a spotting and blighting of the foliage (Figure 3) by the anthracnose fungus, Discula destructiva. Spots are of two types: small, purple-rimmed spots or larger tan blotches that may enlarge to kill the entire leaf. The same fungus, which causes leaf infections also, infects the dogwood twigs. The twigs are killed back several inches and turn tan and dry." Multiple water sprouts (vertical branching) are another sign that a dogwood probably has anthracnose.

This doesn't sound like the trouble you're having. But, even the new varieties are only resistant to anthracnose, I don't think they've developed any that are totally anthracnose-proof, so you should be aware pf these signs, in case your trees do develop this disease.

I'd guess that your current problem might be powdery mildew. I'm copying some info that I wrote for a client about this subject - including symptoms, prevention, and non-toxic treatment.

"Powdery Mildew
Symptoms
Powdery mildew is recognized as a white-to-grayish-white coating on plants, especially noticeable on the leaves and new buds. It can also appear as s cottony, threadlike mat of fungus, usually on the upper leaf surface. The infected leaves may also develop small dark specks, and may yellow and even drop from the plant.

Conditions favoring powdery mildew
Excessive nitrogen fertilization, overcrowding of plants and over watering are preventable causes of powdery mildew. Overcast, warm days with cool nights is another cause. Unfortunately, we can not control this one. This weather pattern is, unfortunately, is common in New England.

Prevention and Control of powdery mildew
Do not handle or work among plants when the foliage is wet. Water thoroughly, at weekly intervals, during periods of drought. The soil should be moist 8 to 12 inches deep. A thorough watering at weekly intervals will grow a healthier plant than more frequent, shallower watering. When you water, do not use an overhead spray - especially in late afternoon or evening. A soaker hose will minimize wetting of the foliage, and it delivers water more efficiently, with less evaporation. Space plants properly, to allow air circulation between plants.

A non-toxic spray to control powdery mildew can be made by mixing 1 Tablespoon of baking soda, 2 ½ teaspoons of cooking oil, and one gallon of water. Remove, and discard, affected leaves. Then spray this on affected plants to minimize subsequent infection."

Thanks, Mrs SP! I do see some vertical sprouting on one sapling, but based on this summer's weather and my past watering habits I suspect powdery mildew is the culprit. However, if I remove all of the affected leaves, there will only be 4 or 5 leaves left on one sapling (about 7' tall). Is that O.K.?

Mrs. SP says 'No!'

Don't remove the leaves, spray w/ oil and baking soda spray (see above)... if it's going to be that many leaves, don't.

Wait untill spring and spray early and often. But, do dispose of the leaves at the end of the growing season so you don't have the spores hanging around.