Ground elder in new and existing borders
On the new and existing garden borders that contain ground elder if you install ground or weed sheeting covered by bark mulch that will stop the ground elder and kill it through lack of sunlight. You can plant through the sheeting with plants by cutting crosses in the sheeting and planting through the sheeting
You will find that some of the ground elder will come up at the edges of the sheeting and sometimes in the crosses you cut into the sheeting to carry out planting. In this case use a small hand held sprayer with Round up weed killer to treat these areas of ground elder as a spot treatment with several applications over the spring and early summer.
With the Round up if you buy it in the litre bottles as it stronger and mix it will 60 percent water here is a link
https://www.ashridgetrees.co.uk/roundup-weedkiller