[mumofstig]

I love the stuff for the fleeting flowers, which remind me of my mum 

BUT It is making a bid to take over the garden. It already has about 10 ft of the border but the suckers were coming up another 4ft further along the fence 
So I've spent most of the day digging out the suckers and as much root as I can, and now my back is complaining

Is there a simpler way of controlling it? any ideas please, as I really don't want to dig it all out

[Trillium]

Sounds like you have the natural wild variety, which sadly suckers like crazy. Digging up roots is the only solution along with a bit of glyphosphate spraying.

In small areas I will plant only hybrid lilacs which don't tend to sucker.

[mumofstig]

It wasalready here when I moved in Trillium, and yes it is the pale mauve 'ordinary' one

If I spray the suckers with glyphosate will it just kill them and leave the main bush unharmed..............or will it all suffer?

[Trillium]

I wouldn't spray the bush itself as there could be small openings that can take up the chemical and kill the whole bush.

What I'd do, if you're not able to dig up what you don't want, is to chop through the roots to the edge where you do want the lilacs to stay, then cut off the limbs close to the root of what you don't want, and spray those top bits. This way the root base is separated from the main section and won't be affected. this is harder wood and may take several sprayings over a few months but should eventually work. Or, you could try a stump remover product.

[mumofstig]

Thanks, I did think of digging a trench across where I want it to stop, cutting through the roots.  I'll do that and then spray anything that appears on the wrong side of it.

Fingers crossed