I live in Pittsburgh. Before fully investigating the potential drawbacks, I bought and planted many trays of english ivy on a slope in my backyard (away from the house). I now do understand the very real risk of spread of this invasive plant. However, if I keep this plant very well trimmed, at least two or more times a year, and not let the ivy climb structures or trees, can the ivy be kept in a juvenile state indefinitely or will it always start producing berries, regardless, within 10 years? All around Pittsburgh I feel that I am seeing ivy that has been kept in check - or is that my misinformed understanding of the situation and should I just 'give up' while I am ahead?
If English Ivy is kept as a groundcover and not permitted to climb, it will remain in the juvenile stage and not produce seeds. However, when growing horizontally (groundcover), the ivy must still be kept in check so that it does not spread to surrounding areas by stem elongation. In the Pittsburgh area where ever there are an abundance of deer, the deer often help keep English ivy in check by browsing, especially during the winter months.
Here's a link for more about English ivy:
As long as you are diligent about keeping the ivy as a non-climbing groundcover,
English ivy will do a good job of covering your slope.