I had a grassy slope at a previous Zone 6 home that was prime real estate for a lawnmower-accident-waiting-to-happen. I decided to convert it to ivy. Mine was probably a 3rd the size of yours.

Starting at the top of the slope, I killed a 1' strip of grass along the top with Round-up and then 7 days later, after the Round-up had done its thing I planted about one dozen ivy plants in the strip (maybe 1' apart?). I mulched the strip heavily (to discourage weed germination) and was faithful in watering the dozen new plants.

As the plants grew, the growing strands were pulled into the surrounding bare spaces. To encourage the strands to root along their length, they were "pinned" to the soil with hair pins. When the ivy approached the grass at the bottom of the cleared strip, I cleared another 1' strip below (so now there was a 2' strip cleared from the top of the slope and toward its base). The process continued until the area was complete.

Ivy is very easy to root, so this is another reason to use it. You can grow many new plants for a nominal cost and these will help to speed your project along and be very kind to your budget.

Vinca minor (periwinkle) does well in those conditions as well. I planted about 15 cuttings last year and my whole slope (length of back yard by 15 feet wide) is covered in purple flowers right now. This area barely gets direct sun but gets filtered sun for a few hours in the morning and a few hours in the late afternoon. It is also helping with erosion control. Good luck!

I too have a grassy slope Zone 5 home that is prime real estate for a lawnmower-accident-waiting-to-happen, a narrower strip about 4 feet across and 40 feet long, not too sunny, sandy soil. I tried the vinca minor, love the little purple flowers, but did not have as much luck as tifbee did with it. In the non-sloped areas (top and bottom of the slope) it took off like gang busters becoming nice and dense but on the main slope of my yard it died out except a sparse amount along the edges. I would love to try it again, lord knows I have enough plants to thin out and use from the top of the slope, do you think mulching it would help and what to mulch with so it still spreads out? :) thanks