Cross pollination is not a problem with roses unless you are a rose breeder.

You know that they will be deciduous, right? No privacy in winter.

Hopefully the hedge is oriented in such a manner as that each plant gets sun for a while on both sides of the plant (the sides that are not next to adjacent plants). This makes a fuller denser plant.

Hopefully your area is not infected with Rose Rosette Disease, which has the potential to ruin all your plants. Something to check into first.

It sounds beautiful! I would put an evergreen hedge in with a row of roses in front of it on your side with a little room between to maintain the roses. I have seen this a few times and even used a similar idea here but instead of a hedge, I used a wall creeper as the green backdrop.

The green backdrop looks nice when the roses are cut back or dormant and if they lose some leaves, you still have the green from behind coming through so it looks great all the time. Then all you see is wonderful flowers against beautiful green no matter what.

A rose hedge will add beauty to your lot line, and who can complain about that!? I do agree with above posters that you want to make sure you are in full sun, and you may want to check with your local rose society if Rose Rosette Disease is a problem in your area. It's alot of work, and expense to lose that kind of hedge to disease.
As far as planting both colors, I think this would look beautiful. You may want to ask if both colors grow at the same rate if it is important for you to have an even hedge, I'm not sure of that answer.
Lastly, this won't be a privacy hedge most of the year in Pennsylvania, so make sure you consider this, and I agree with including an evergreen would look lovely and add a bit of privacy.
Come back and give us a picture when you're done!

Not too long ago, someone posted on this forum a picture of a hedge (in front of a natural-colored fence) consisting of alternating red Knock Outs and pink Knock Outs (or it might have been red double Knock Outs and pink double Knock Outs--either should work). It was gorgeous and probably the most bs-resistant hedge you can come up with.

If the creator of that hedge is reading this, please post the picture again. In the meantime, I'll wrack my brains to see if I can remember who that poster was or what the thread was called.

Good luck.

Kate

Roderick, I found that picture of the alternating Knock Outs (red and pink). Here is the thread: thread about KO Hedge

A picture of the gorgeous hedge is shown further down the page, or go to the link below to see it .

Kate

Here is a link that might be useful: Picture of Knock Out hedge

Thanks to all who replied. I will continue to learn over the winter. Since I retired in 1987 I have spent my time learning cabinet making. our previous property had Norway spruce on East, North and West. The South was open but the nearest neighbor was 1/4 mile away. We had to downsize. I'm 85 and couldn't keep up with a large property. My only experience with flowers was a large wildflower garden. Over time I learned that many weeds have lovely flowers. BTW this is my first experience living with close neighbors. I've been blessed with great ones so privacy is not of great concern to me. Thanks for the photo.

I checked on Julia Child floribunda that Diane recommended. Height is reported to be 25 to 31inches. I am planning to maintain the knockout hedge at 4 to 5 feet and don't think I would like the stepped look. Comments anyone? Doug

A Julia Child will easily go to 5 feet, this is a picture of mine taken in the spring. (5/19) By the end of the summer it was over the fence line. If you planted yours a bit closer than I did it would be an outstanding hedge. My only worry is this rose for me does get blackspot, but where I live most of my roses get some blackspot. Others on this site have stated Julia Child has been completely healthy for them.
(Blackspot is a fungal disease that causes spotting on the leaves and eventually they yellow and drop off. It does not kill the plant, but for me if this rose isn't sprayed the plant can look quite sickly by the end of the season.) The advantage to knockouts is they don't normally get blackspot. On the other hand if you want a rose with many more petals Julia Child is just gorgeous.

Here is a close up of the flowers. By the way the best thing about this rose is it blooms like crazy all season long. I do deadhead mine regularly though, and I hear you don't have to deadhead knockouts to encourage blooms. Maybe someone else can chime in if they don't deadhead Julia how does it bloom for you?

This post was edited by mzstitch on Tue, Nov 19, 13 at 7:48

Lovely pics of Julia!

I don't know how tall Julia gets, but if you are contemplating a red Double Knock Out, it may not get 4-5 ft tall. I grow two, one in full sun and other in much too much shade. The one in full sun grows about 3.5-4 ft tall; the one in the shade grows 5-6 ft tall but only because it is desperately reaching for more sun.

The regular Knock Out grows a bit taller than the Double Knock Out--sounds like it is closer to what you are looking for, in terms of height.

My understanding is that BS disease is a big problem in Pennsylvania, so if you do not want to be plagued with BS problems, you should probably stick with the Knock Outs. There is a yellow Knock Out called Sunny Knock Out--it is a single like the regular Knock Out is and gets about 4 ft tall, maybe a shade taller. You would have to check and see. Obviously, it is BS-resistant. The problem with the yellow Knock Out is that it opens to a more mellow yellow and then fades quickly to nearly white. However, it puts out lots of blooms, so there is usually a combination of mellow yellow and ivory blooms at any one time. My neighbor grows it and I find it quite charming. It wouldn't afford you the dramatic contrast you may have been looking for, but it would be attractive and disease-resistant.

A different route you might take is to plant Home Run roses instead of Knock Outs. Home Run is a bright red single and NEVER has disease problems. It is a good bloomer and rebloomer. The only drawback is that it may not get quite as tall as you wanted. After 3 years, mine are reaching 4 ft, but I don't think they will get much taller than that. (Home Run is a distant relative of Knock Out, in case you were wondering.)

Here's a picture of Home Run, when it was two years old. It is taller now. Mine are planted about 4 ft apart because I wanted a bit of space between them. For a more continuous hedge, you could plant them 3 ft apart (from the center of one plant to the center of the next one).
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Here is another pic:
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Oh yes, one other point--on pruning. Again I don't know about Julia, but as far as Knock Out goes, it does not HAVE to be pruned, but if you don't deadhead it at the end of each bloom cycle, it is going to look rather awful for a few weeks with all those dead blooms on it.

Home Run also doesn't NEED to be pruned, but it also looks a bit better if the dead blooms are plucked off. Home Run is a rather handsome bush most of the time, however, even when it is totally green in between bloom cycles.

Hope that helps. If you don't know the site I've linked you to below, you might want to explore it. Lots of information about just about any rose in existence.

Kate

Here is a link that might be useful: Sunny Knock Out at helpmefind.com

Roderick, just remembered that there is a yellow Carefree Sunshine that comes from the same breeder and is very disease resistant--looks kind of like the Sunny Knock Out. I don't know much about it--maybe it isn't quite tall enough for your purposes--not sure. You might check it out below and post a query here if you are interested.

Kate

Here is a link that might be useful: Carefree Sunshine at helpmefind.com

My two Julia Child roses are 6 X 6 feet. I can't believe those puny size predictions even in zone 6. In this pic, the smaller rose down in front is Bernstein-Rose, about the predicted size of JC. The actual Julias are farther up the sidewalk. You can see the size difference easily. Diane