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shadygarden_co

What should I do with roses to prepare them for winter?

shadygarden_CO
15 years ago

I have lots of powdery mildew on my climbing roses, also probably black spot, in addition to bugs of some kind in my regular rose bushes, in the blooms. There is also mildew on Ballerina.

Should I spray for the mildew and should I try to cut off all the stems and leaves that have mildew? I am sure tired of fighting that mildew, which I have been doing all summer, pretty much. I was spraying with either Neem or with a Cornell-type formula of Ultra Fine oil and baking powder. We haven't yet had a freeze here in Denver, and I am thinking maybe a freeze would kill some bugs, but probably not the mildew.

Also, do you cut down perennials such as Coral Canyon Diascia and mums? The Diascia looks great right now, but maybe I should cut them before winter really sets in.

Any advice would be appreciated.

Marlene

Comments (5)

  • david52 Zone 6
    15 years ago
    last modified: 9 years ago

    Marlene, I'm not a rose expert by any means, but I do have a lot of roses that manage to get a lot of diseases, and I've only killed a few. Over the years, I've tried selective pruning in the fall, selective pruning in the spring, and now, I just whack everything off about 4" above the graft in mid to late April.

    I think the idea with leaving everything over the winter is based on the concept that pruning stimulates new growth, and the inevitable warmish spells over the winter mean the rose growth gets started and then gets walloped by much colder weather.

    So right now, all of mine that didn't get frozen a few weeks ago are covered with powdery mildew and black spot, and I'm trying my hardest to ignore them, and if I have to look at them, I consider all these diseased plants as "winter interest."

    I dunno about the mums. I leave mine up until sometime in April as well.

  • Skybird - z5, Denver, Colorado
    15 years ago
    last modified: 9 years ago

    Hi Marlene,

    Im not much of a rose grower either, but IÂve had surprisingly good luck with the five that were in at this house when I bought it. Mine are all teas, and IÂve already cut mine down for this yearÂto about knee height. In spring IÂll trim out any dead wood and give the canes a fresh cut. The year we got all the snowstorms, I hadnÂt gotten mine cut down, and I had serious damage to my favorite one, a yellow, when the snow piled up on top of it and broke a couple of the main canes. Now I try to be sure I get them done before weÂre likely to get any heavy snows. But if yours are climbers, and they bloom on old wood only, you wonÂt get any flowers next year if you cut them down before they bloom, so when you cut them down would really depend on if they bloom on old or new woodÂand if youÂre willing to cut them down short and let them start over again.

    With the mildew, I can give you all the canned answers from when I was in the green industry, but the ONLY thing IÂve found to help prevent mildewÂand rustÂand black spotÂetc., is to keep them really well watered. Every year IÂve been better and better about making sure they stay well watered, and this is the first year I havenÂt had a problem with any of the funguses. And when I first moved in (the people who were here before me thought they were taking care of the few plants that were here, but they didnÂt know ANYTHING about plants) two of the roses were badly infected with rust and mildew. I never used any type of treatment, other than picking off badly infected leaves (to the point of defoliating those two a couple times) and throwing them in the trash. I donÂt know what the oils doÂIÂve never used them and have never heard of them being recommended for fungus, especially in summer, but the fungicides you can buy, along with things like baking soda (milk is supposed to help too) donÂt actually "kill" the fungus. I donÂt think thereÂs anything that does that. They just help slow it down somewhatÂsometimesÂor help keep if from starting if theyÂre not infected yet. And, since I rarely get rain, the leaves on mine tend to stay pretty dry, but I donÂt make any special attempts to keep them dry. As a matter of fact, I water my grass after dark and IÂm sure the mist gets blown onto the roses and they probably stay wet much of the night when IÂve watered. I donÂt believe, anymore, that that makes any difference! They seem to get better and better, the more, and more thoroughly I keep them watered. IÂve also noticed, when IÂm in Illinois visiting family, or any of the other very humid places I get to, that I rarely notice mildew on roses, or anything elseÂyet, here in Colorado it seems to run rampant. Since high humidity and wet foliage is supposed to promote mildew, that seems just a teensy bit backwardsÂand I think that theory is bunk! Just my personal opinion! I have come to the conclusionÂrightly or wronglyÂthat stress (the plant--not you!) is the primary cause of fungus!

    If you decide to wait till spring to cut them down, I do recommend putting on a pair of leather gloves and cleaning off as much of the foliage as you can, and picking up whatever is around the base of the plants. Getting as much of the mildew as you can out of the area is always a good idea.

    With the mums, I cut mine down in fall or over winter when the weatherÂs nice. I got one of mine cut down a little over a week ago, and the new growth at the bottom will pretty much just sit there smiling at me till spring. Actually, my plants are getting old, and next spring IÂm gonna dig them up and replant new sections of the plants. If they knew that, they might not be smiling!!! The rest of them IÂll be cutting down as soon as I find timeÂso I can see that "new foliage smile!". And I cut the individual stems all the way downÂless than an inchÂto the new growth at the bottom. But I donÂt really think it makes a whole lot of difference if you leave the old growth on over winter, or cut it off! I just like everything to look "neat" over winter, and, also, if I wait till spring and donÂt get around to it until after theyÂve started to grow, itÂs harder to cut them down without damaging the new growth.

    With the Diascia, IÂm not sure what to recommend! I was at PaulinoÂs the year that one was introduced thru Plant Select, and at that time we were never able to decide for sure if it was reliably hardy. If IÂm not absolutely sure something is gonna come back, I usually donÂt cut it all the way down till I can be pretty sure of the weather in spring. So you may want to leave it just as it is, or cut it halfway down, but leave at least some of the stems/foliage on over winter. IÂve never grown it myself?

    I like winter interest too, David, but I guess my "interests" just fall along different lines! ;-)

    Skybird

  • shadygarden_CO
    Original Author
    15 years ago
    last modified: 9 years ago

    I just love this Rocky Mt. forum. I posted this question here rather than the Roses forum because I thought I would get answers here, and I was right! So thank you, David and Skybird.

    I feel better about the sorry condition of my roses now and I think I will more or less strip the leaves from my climbers, at least the ones that have mildew, and just wait until spring, maybe even water now on a warm day, but in spring, water well.

    BTW, all my roses are own root. but I also have mildew on some shrub roses, like Ballerina and Morden Blush. I know Morden Blush also has some kind of insects in the blooms.

    Has anyone tried getting beneficial nematodes in the spring to put in the soil to get rid of thrip eggs or whatever is in the soil from thrips? I thought I'd do that.

    Anyway, if anyone has further advice, that would be great, and, again, thanks to David and Skybird for their help.

    Marlene

  • david52 Zone 6
    15 years ago
    last modified: 9 years ago

    I dunno what rose disease I picked up a couple years ago, but its the one that, in the early spring, the plant starts to bud out and then the entire stem turns black and dies back to the graft. Later in the spring / early summer, the disease goes away and the plants do just fine.

    So I was pruning them in early spring, and then I'd have to go around and re-prune again. I need to count again, but I have something over 50 rose bushes. Pruning all that takes a couple of days and results in an awful lot of thorny stuff to throw out, and my forearms and face look like I tangled with a mountain lion -.

    Actually, this year I'm sorely tempted to whack the things back now and get it over with. "Winter interest" which consists of diseased plants is, well, iffy. Maybe I can just grab a few rose hips and put them in a bowl or something.

    I need to lay down compost in all the beds, and it would be a lot easier if I cleaned them out now.....

    Every year, when it first snows, the deer come in and clean off all the rose foliage in a couple days. Then they come back in the spring and clean off all the new growth too. So perhaps I could break this habit.

  • shadygarden_CO
    Original Author
    15 years ago
    last modified: 9 years ago

    Well, I decided to take David's advice today and started defoliating my climbers -- and I really do think I would have to pretty much completely defoliate them, if I ever finish the job. However, I noted mildew on the canes, too, right by the thorns. Should I cut off the canes too?

    I'm tempted to just leave them alone, but will probably spray them with the Cornell formula thing, as I have a rose book or two that recommends that.

    I also watered them and will continue to do that a good deal next spring.

    Thanks again, all.

    Marlene