The only roses that get powdery mildew in my garden are the huge ramblers that can't be watered from overhead. The leaves at the top never get watered after the rain stops coming down here in April or May.

It think powdery mildew is not really related to bathroom mildew.

I don't know about the leaves, but I was told many years ago that keeping rose roots well watered prevented powdery mildew. And from experience, this seems to be true. I only get powdery mildew when I let a rose dry out too much. Since many of mine don't get any overhead water other than our pathetic rainfall, this seems to be case for my roses. It probably helps that I have great air circulation.

FWIW, I found the same to be true for african violets. If I keep them from drying out, they don't get powdery mildew.

Did some quick research on powdery mildew. Here's why watering makes the white go away:
-
http://scvrs.homestead.com/Mar...

Powdery mildew affects roses grown in dry climates and is common in much of California, including the Santa Clarita Valley. Caused by Sphaerotheca pannosa var. rosae, it forms a white, powdery film on the leaves, stems, and flowers of infected roses. Young peduncles, sepals, petals, and stems become twisted and distorted and new growth buds and growing tips may be killed.

Powdery mildew is common in the spring and fall when warm days are followed by cool, damp nights. Spore maturation and release usually occurs during the day when the relative humidity is low. At night when temperatures drop and the humidity increases, spores germinate and the fungus penetrates the plant's surfaces. Spores need low humidity, warm temperatures, and dry leaves to mature and be released, hence the advice to hose off the leaves of infected plants during the day. The only caveat being that the plant must be dry by nightfall.

Again, prevention is the best cure:

Plant resistant rose varieties
Plant them far enough apart to allow lots of air circulation
Plant in full sun
After pruning, strip the leaves from your roses and discard to the trash
After pruning, use a dormant season horticultural oil spray
During optimal growth conditions, wash all surfaces of the plant with hose water.
Do so early enough in the day that the leaves dry out before nightfall.

One of the easiest ways to control powdery mildew is to give your roses a thorough wash at least two mornings a week. A morning bath raises the humidity so spores can't mature. Free water left on the plants also discourages spore maturation. Plants must be dry before nightfall so residual moisture does not provide favorable conditions for spore germination.

Powdery mildew is attracted to lush, new growth. Rosarians growing for spring shows feed their plants heavily early in the year in order to have roses ready to cut. If you are not pushing your plants for a show, try cutting back or postponing the early spring feeding.

---

That would explain why I don't have this problem for the most part. I've seen white powdery only once, last year, on Orange Velvet & Rose Marie Viaud. Cut off those leaves never saw it again on anyone.

Ah, now I know why my roses are not bothered by powdery mildew! Between our humidity and my lax care practices, they are well protected!

Very informative!

porkpal said:Ah, now I know why my roses are not bothered by powdery mildew! Between our humidity and my lax care practices, they are well protected!

Yeah. I've only seen it once in my garden, too.

This guy was labled Mr Lincoln over at Lowes today. The bloom was a purple lavender color. Is this true for the bloom, I thought MrL was a deep red?

My Mr Lincoln is a true deep red that fades a bit with age, however never as much as your photo shows. Reds are hard to photograph; is the color of the rose posted true to life?

Pretty close, since I wasn't using my dslr its hard to make it exactly but it was mot red but this purple hue instead. Does Mr. Lincoln fade to this possibly? There were no other blooms on the Bush.

The blooms on MR. LINCOLN blue with age, and I've seen some really old flowers look pretty purplish, so that might possibly be it. Does it have a heavy fragrance?

That's what one of my MrL's turns into in the shade after about a week or so. Very very blued out like that. That's why I love MrL.

Betty I believed it did.

Toni, maybe it is then and I just caught it at a older stage. I wish it had additional blooms.

Another thing you can look for is thorns. Intrigue, which is pretty close to that mauve there, doesn't have the huge "cats claws" type thorns that MrL has. New growth is always a deep deep burgundy color and the canes are stately & long, like a florist's rose. At least in my experience that's what I look for. But it *definitely* does look like Stephen's Big Purple http://www.helpmefind.com/rose... If it is, then I'd personally snab it up 'cuz I've been looking for a SBP for a few years and never found one locally, let alone at a big box. But I have found Peter Mayle at Lowes before, and an aging flower does look like your mystery purdy. http://www.helpmefind.com/rose... I don't think it's Voluptuous!, though.. V is more fuchsia and not as blue.

Is it possible to have a discussion about roses and mildew without talking about Dorothy Perkins?

Just over a century ago Jackson and Perkins introduced the wichurana hybrid Dorothy Perkins. It was a vigorous - almost rampant - climber that gladly clambered up over arches and pergolas and produced acres and acres of light pink flowers. People designed whole gardens around it, erecting rustic wooden structures just to give Dorothy Perkins a place to live. Inside of about a decade Dorothy Perkins had transformed how people thought about rose gardening. Beds were out. Pergolas were in. Jackson and Perkins sold millions of plants. Everyone was fat and happy.

Then mildew struck. In a short period of time virtually every Dorothy Perkins harbored the blight. Plants shriveled up, looked ugly, died. The pergolas aged and started falling apart. People throughout the anglophone world angrily tore down the pergolas and tore out the roses. Instead they planted pansies or marigolds or else they just laid down sod. That was pretty much the end of the artful use of rambling roses in the garden in the US. In Britain the story was similar but a little less exaggerated. Roses such as Chaplin's Pink and Albertine still arch high over many thousands of British gardens. A number of Barbier's wichurana ramblers are in distribution in the US. Then there is New Dawn, not quite a rambler, but often as big as one and enriched with wichurana genes.

In the intervening century more robust roses have been introduced such as Super Dorothy. And the popularity of rambling roses that were more mildew resistant has grown slowly. Lots of roses have been bred from the tough wichurana climber New Dawn. And there has been some small interest within the rose growing community in other good old climbers and ramblers. Smart people who understand the great decorative advantages that ramblers can bring to the garden - such as Zuzu - have been undeterred by the trend of eschewing climbers, using them generously to decorate their gardens. Perhaps it is wishful thinking or projection on my part, but I seen climbing roses playing an increasing role in the garden.

--


P.S. There are many things we can learn from the story of the rise and fall of Dorothy Perkins, but the one I think about first is the danger of monoculture and its built-in susceptibility to blight. See also the Irish potato famine.

PPS. It's never been clear to me why it was Dorothy Perkins that stole the show. Even at the time of Dorothy's popularity there were a lot of other good wichurana ramblers. And a lot of good multifllora ramblers, too. The ARS rates a number of ramblers more highly than Dorothy Perkins. Newport Fairy, for example, has an ARS rating or 8.6 vs. Dorothy's 7.4.

PPPS. I guess we need to better understand how to control mildew in our gardens. Overhead pressure washes with a little soap and a light potassium bicarbonate rinse starting at 10:00 AM, blow dry at 11:00?

I don't think I've ever seen potassium bicarbonate in stores. Would you find it at a place that refills fire extinguishers?

Cindi - found it on amazon

http://www.amazon.com/gp/aw/d/...

Well taking the wet the leaves advice I can say that I am seeing great improvements day to day. Very little mildew remains as I wet the foilage every morning so it dries before evening. Sorry not the best image lighting.



On a different note, here is the newest addition, picked out by the DW, to my small yet developing rose collection. Pink Promise.

Your Pink Promise should be showing more pink as the bush gets older. I've noticed that the first blooming flush will look different than later flushes. PP that I've seen here is always a lot more deeper in pink than that one. But the heat could have faded it, too. But glad that the mildew is going away!

Your wife has good taste Jake, that's a real feminine beauty of a bloom!

That should be interesting to watch for Toni. I know with daylilies, climate has a play with bloom color, a cultivar I have may be a lot lighter than one that my dad carries up in the mountains. I don't know if it applies to roses as well.

Thank you sue!