The only thing I can add is that the lilac/ash borer and the emerald ash borer are two different insects. The emeralds borer is by far the most damaging to the ash tree From reading it seems the lilac/ash borer does not seriously harm mature ash trees.

However there are a few cane hardy rose varieties that would do well out there. Depending on the weather they may need supplementary water for the first year or two. You should be able to find both once blooming and repeat hardy varieties.

What will work depends on where you are.

I'm zone 5.

Sorry, Patty W., are you saying the lilacs are likely all right? I'd prefer them because of their greater height next to the very tall ash.

I'm nervous about picking out roses. My only experience was selecting Gertrude Jekyll because it sounded so lovely on David Austen's site, only not so perfect in reality. Rose write- ups are always intoxicating; best to get the advice of real people but no one around me grows roses.

If you want a shrub like rose that would not suffer a lot of winter dieback you should look into the canadian/explorer roses. Also do a search of roses for zone 3-4. Will narrow your options quite a bit. These will be hardier for you. You may also want to say what colours you like for suggestions.

Are you planning to do circular hedge or a straight line? I was not too sure of your plan from your description. So depending on what you were meaning; I was thinking was why not do a mixed plant/shrub hedge from tallest to shortest for an example. 70 ft is a lot of space to plant.

Yes, some criteria would help. If roses, I'd like to plant medium to deep pinks. The hedge is straight (running east/west) because what you can't see is a row of white crab apples to the right, running north/south. A garden shed is going in behind the to-be lilac/rose hedge. From my kitchen window (left/west) I will have a view into this space, which will then be populated with some perennials.

Will look into Canadian roses. We need to grow hardy varieties. We have seven acres and are in our seventies so we reserve fussy for the area close to the house.

Thanks