sorie6(6b ok.)August 29, 2010

Is there a Colo. forum for roses? I sure can't seem to find one!!

My roses have black spot and gets it every yr. I want to try to prevent it next yr. I clean up good but guess it's in the soil? Thanks

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treebarb Z5 Denver

There isn't a Colorado forum for roses that I'm aware of. Maybe there should be, since we have such a different climate. Black spot pressure is lower here than in many areas of the country. But some roses are just more prone to it. What kind of roses do you have?
Bayer makes a good drench for roses that can also be mixed as a spray. If you'd rather not use chemicals you can remove the affected leaves and they will come back, but the rose will look pretty bare for a while. I fertilize my roses in early spring and then again in late June or early July. This time of year I don't fertilize since I don't want to encourage new growth that will freeze.
Do you water overhead? It's better for roses to water the base and try not to splash the leaves. I water mine by hand. I keep a good layer of mulch under them and keep it pulled back a few inches from the base of the plant, but the wind here often piles it up on the rose anyway. But I keep pulling it back.

    Bookmark   August 30, 2010 at 8:45AM
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Skybird - z5, Denver, Colorado

Hi Sorie,

IÂm not in any sense of the word a rose expert, but I do have my own theories on the subject of fungus on roses! IÂve copied part of a reply from a thread a couple years ago that was asking about powdery mildew, but black spot, mildew, and rustÂwhich was my worst problem, are all funguses, and what works for one, should work for the others. And, definitely do throw any infected leaves in the trash to get rid of as many of the spores as possible, but theyÂre already in the soil, so the potential of developing a problem is always there, whether we like it or not.

What IÂve copied below is entirely my own theory, but it still seems to be working for me, and is the best thing IÂve found so far. I DO remove any leaves immediately if/when I do occasionally see a few with mildew/rust/black spot.

Copied from a November Â08 post:

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 here, 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. The fungicides you can buy, along with things like baking soda or milk sprays 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 (another no no!) and IÂm sure the mist gets blown onto the roses, and at times the sprinkler actually hits them, 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 high, dry Colorado it seems to run rampant. Since high humidity and wet foliage are 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 plant stress is the primary cause of fungus!

    Bookmark   August 31, 2010 at 3:00AM
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sorie6(6b ok.)

Thank you. Mine get it every yr. I've cut them back severly 2x this yr. I clean up leaves but I'm sure I don't get them all. They do get watered with the sprinkler around 4am. 3x a week. They are also very old 25+ some maybe I need to think of getting rid of them. I'm sure I could find something different and fun to put in the garden.
If I remove them will the spores stay in the soil even tho I ammend it? Thanks

    Bookmark   September 1, 2010 at 10:51PM
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Skybird - z5, Denver, Colorado

Hi Sorie,

The spores for all those funguses are ALWAYS around. Fungi have been around since LONG before human beings were here, and will probably be around long after human beings are extinct! Whether any of the funguses actually develop on a given plant depends on the plant and the conditions in which itÂs growing.

As TreeBarb said, some roses are more resistant to them than others. If the ones you have are very old varieties, they may be more susceptible than some of the newer varieties.

Before you get rid of them, IÂd recommend changing the way youÂre watering them. Water them DEEPLY two or three times, a week or week and a half apart and see if thereÂs any improvement in the new growth. To do that, lay the hose at the base of each plant, turn it on a trickle, and leave it there for at least a half an hour. That will water slowly enough that the water will soak in deeply. Especially if these have been in that long, their roots go deep, and frequent, short watering periods will only keep the surface wet, and not water down to the depth where the roots actually are. You "should" have time yet this year to see if itÂs helping at all.

If you should decide to get rid of them, IÂd recommend checking to be sure youÂre putting in something that isnÂt especially susceptible to black spot, or any of the fungusesÂrust, mildew, since you know for sure that that area is heavily infested with the spores.

Good luck,

    Bookmark   September 1, 2010 at 11:29PM
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sorie6(6b ok.)

Thanks. I've just decided to dig them out and amend the soil and plant a garden for birds and butterflies!!
thanks again for all you suggestions.

    Bookmark   September 21, 2010 at 10:26AM
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treebarb Z5 Denver

Skybird, I really enjoyed your thoughts on watering/disease resistance. It actually got me watering mine more frequently and I'm glad with the unrelenting heat we've had this summer.
Sorie, go for it! Life's too short to not plant what you want.


    Bookmark   September 22, 2010 at 7:48PM
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sorie6(6b ok.)

Thanks. The roses have given me so much pleasure over the past 20+ yr. but it's time to move on. Want to attract more birds and butterflies. Wish me luck.

    Bookmark   September 23, 2010 at 7:51PM
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dsieber(z5 (Lakewood CO))

For the past 7 years our roses have been fantastic. The secret is having irrigation injectors next to the plants and plenty of mulch. Every spring we prune them back hard.

    Bookmark   September 23, 2010 at 11:11PM
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You might try planting your new stuff in and around the existing roses, pretending they aren't there. Whack them back in the spring and then ignore them, so to speak, and they'll come back in late summer and surprise you.

We had over 60 roses, and then along came the something-something disease that turns the stems black, eventually killing that part of the plant. The only way to deal with it is to cut the entire plant back to the nubs in the spring and hope for the best. Some die, some survive, we just ignore them and then consider it a blessing to see them blooming later in the summer among the other plants. This year we had a few bloom that I'd hadn't seen for a couple of summers, just a single bloom popping up out of the middle of something else.

    Bookmark   September 23, 2010 at 11:13PM
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dan_staley(5b/SS 2b AHS 6-7)

Some years ago, I wanted to be a rosarian. Then I got tired of all the work and chemicals. It is a choice, surely. I do miss the fragrance, tho and the puttering.

And I will say that the heat and no rain this year really showed up on our recently-received water bill this month, as there is a new bed and some new turf and the veggies...ugh.


    Bookmark   September 23, 2010 at 11:58PM
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