Monster plant taking over what is it

[cansu]

Trying to sort out jungle style border. What is this? How do I get rid of it or tame it?

cottoneaster

herringbone cotoneaster one...I have it in my garden and it can be pruned hard to control it

Thank you. Should I just cut it back very hard?

it's probably self seeded.

you can shape it like topiary.
it has pretty white flowers that insects like and the berries are on the menu of many birds.
sorry I don't know the name...

(and they can be great ground cover if you have issues with shitting cats in your garden)

This is one near me which has been pruned hard to the shape of the wall. The side facing the house is much thicker so birds can get between the branches but the top of the wall is so neat.

They're good for covering manhole covers in the garden too. Tough as old boots so just hack it back to where you want it. Fab red berries in winter, birds love them.

Birds and bees LOVE it!!

Cotoneaster horizontalis, a splendid plant that will withstand any amount of pruning you give it.