The instructions on fertilizer packages provide for generous feeding. Don't exceed the labelled dose/interval and don't double up with other fertilizers in the same interval.

If you have sandy soil, you could apply a 1/2 dose of solution every two weeks. If the soil contains some clay, a full dose every 4-6 weeks is fairly standard.

I wouldn't expect the vinegar spray to have much effect on blackspot. Where do you live and what kind of roses are you growing?

I fertilize once in spring and sometimes once in summer.
spring is a combo of rose or garden tone and 10,10,10.

Summer is hit and miss. sometime one of the tones or 10,10,10.

Water seems to be more crucial, the roses in the wetter spots seem to be the happiest.

I didn't get a good summer or fall flush last year and I didn't fertilize in summer but i know people around here that did fertilize and had the same problem. I think it was all those days in the 100's and it hardly ever rained. I'll be doing both a summer fertilizing and make sure they are well watered.

i live in green country oklahoma, humid, wet, rain.

i read of a person who swore on vinegar/water to prevent black spots. any better ideas?

i have new dawn, b.r. cant and lafter roses

More effective organic sprays are micronized sulfur, oil/bicarbonate mixture, copper soap, and antitranspirant. See the organic roses FAQ. Sulfur and oil/bicarbonate will burn foliage in hot weather.

More effective than the above and less toxic to plants are the synthetic fungicides Bayer Disease Control (not the combo products), Honor Guard, and Bonide Infuse.

I wouldn't spray vinegar on my roses. Mrs. B R Cant will do fine with no spray, and New Dawn should also. I don't know if Lafter will, but there are many many roses that do not need spray.

Sometimes when it rains here, we can get spots, I am not even sure they are black spot, but the leaves will drop and be replace quickly, and many roses don't need spray.

Our weather now is terrible. It is way too hot, and we have had an unusual amount of rain.

I fertilized mine about a month ago. Now that the termperatures are at or a little under 100, you might be careful with the fertilizer. Some people here know more than I do about that.

Sammy

Thanks, and hi Sammy,

My New Dawn had black spot last year and lost all of its leaves and they didn't come back until this year. But it was in a bad spot where other plants were in front of it. This year I moved both of them and gave the one away that had black spot, but it looked good this year. Just no room for more.

I will just fertilize in spring and once in summer.

Sammy, it sounds like you don't spray for black spot.

if they start to get black spot i will get the bayer then. i wanted to go organic.

Thanks.

Because you mentioned vinegar sprayed I thought you might be interested in organic method rose growing.
I'm an organic method gardener who used to spray my roses with Cornell spray.
Cornell university spent some years developing an organic method spray for roses. It is cheap and easy to make and works by changing the ph. upon the rose foliage to prevent blackspot, powdery mildew and rust.
It must be re-applied after rain or sprinkling, and it works best as a preventative measure, spraying before disease shows up in spring before leaflets are full sized, and repeating spraying every 2-6 weeks.

Cornell spray recipe
2-3 tsp. of baking soda (3 tsp. will be more effective but leave a faint coating of that white powder)
1 quart of water
1 tsp. of Canola oil. It must be Canola because this oil disperses in water. The oil makes the solution stick to the leaves.

Over the years I got tired of spraying my roses, after all none of my other garden plants need spraying, so when I have moved, I've left behind my roses that needed spraying , and now I only grow disease resistant roses and ignore a bit of fungal disease.
After decades of gardening I've come to have the opinion that there is not a rose on earth so beautiful that it is worth poisoning Mother Earth for. I've tried to voice this opinion softly because I would not wish to pontificate.

Luxrosa

thanks so much. will try to organic spray