I would use Drift roses instead -- KO's would grow too large without frequent pruning.

Here regular Ko's spread to 4-5ft wide/ 5-6ft tall if left alone so probably to large for your application...

Double Ko's are about 3+ft wide here & 4ft tall... I prune ours down to about 20" tall each Spring and by fall they are 3+ft wide by 4ft tall...Not sure how big they would get if left alone...

Drift roses do not do well here no spray as they blackspot... So maybe find out if they would work in your New Jersey area....

Flower Carpet does good around here...

Maybe someone from New Jersey will chime in...

I'm not in the nj area but we get a ton of black spot and my drift roses look great . Now your climate is closer to jims than mine but I thought I would throw that out here. I have the apricot ones I believe. They get large but not too large. Everyone is right about the ko getting too large . They sneak up on ya !

*sigh*

i thought I'd finally found a solution. It's a really problematic area of my garden - a very long narrow-ish space on a very busy street, and right in front of my house, so highly visible. Full of weeds no matter what I do or plant there.

From what I've read of KO roses, they have a long bloom time and are very strong. Oh, and my favorite local nursery has 20 gallons for $10 each . . .

What if I planted them on the inside of the fence - would they spill out and over nicely?

I have a neighbor who planted ko inside her white picket fence. It juts up and out from between the slats and over the fence. It does not drape.

Perhaps plant a lax climber with no thorns on the inside if you want that cascading look. I just got Reve d'Or and it seems to pretty flexible canes and has little thorns.

I'm in Central NJ - yes, KOs get big here, though Rainbow Knockout seems to stay smaller. I think they would probably spill over your fence nicely if you left them unpruned (it would take a few years) but of course that doesn't solve your issue with your weedy problem area outside the fence. Drifts are good for me, don't get much in the way of BS, they might work well, though they are thorny. I particularly like Sweet Drift and Pink Drift. Flower carpets would be a good choice too. The only thing is, you want to get the worst of the weeds tackled before you plant the roses, because even with ground cover roses, they won't smother all the weeds. So I'd do cardboard and mulch to smother the weeds before planting.

Thanks @Frances - I've tackled them before and have a new plan for doing away with them for good this time, but slowly and more carefully instead of the kamikaze approach I took before. One patch at a time with cardboard and mulch around plantings. The double KO's I found are from Gasko's - and they're magnificent.

lilyfinch....what's the light green leafed plant in front of roses ??

Rabainsz - it's a hosta .. I wish I could remember the name . I picked them at homedept and they were cheap so they must be a common one. They do really well for the amount of sun I get .