Q.Does Established Hypericum Calycinum Prevent Weeds?
We have a stream bank about 10′ x 100′ that receives about 4 hrs. of morning sun and the rest of the day is light shade. Beautiful ivy has been on the very steep stream bank for decades. Deer or something else has has removed most of the foliage, leaving only woody stems. Hypericum calycinum seems to be a great alternative as it flowers and is supposed to be deer resistant. My only concern is weed control. I am 71, so constant heavy weeding won’t work for me further down the road. Also, will this species tolerate my stepping on it for light weeding, fertilizing, pruning, etc.?

Certified GKH Gardening Expert
You are in zone 7a, which should be fine for this particular ground cover.
https://www.gardeningknowhow.com/garden-how-to/gardening-by-zone/zone-8/zone-8-ground-cover.htm
Know that the plant can become invasive, which could cause you some problems down the road. I imagine that weed problems will depend upon how close together you plant the ground covering, as well as other factors such as soil, sun, etc. Here's an article that discusses dense planting for weed control - hope this helps:
https://www.gardeningknowhow.com/ornamental/flowers/fgen/planting-flowers-to-deter-weeds.htm