Question
We have a house that the backyard is a very steep hill upward. We have cut down trees to allow light to the house but the vegetation went wild. We have cleared a lot and used a vegetation killer. Next year we would like to build a multi level deck into the hillside and plant a groundcover such as ivy for easy maintenance. How long until we could plant it after using the vegetation killer and what would we do until the ivy gets thick enough to choke out most of the weeds. Or is there another solution we haven't thought of.  Thanks in advance. We live in OH,

Answer
Weed killers usually dissipate in about 6 weeks, unless specifically formulated to last longer (like weed killer for driveways)

As for groundcovers, there are lots of options.  I would lay down a weed barrier under the deck. As far as other plants on a hillside, you might want to also consider Juniper (slow grower), or Wintercreeper (fast)  For flowering groundcover, consider Memorial Rose, Meidiland Rose, Cotoneaster, or Mother-of-tyme.   Consider the slope orientation, too - is it sunny (south-facing), or in shade (north-facing)? Pick accordingly.

Check out Ohio-appropriate plants at the Ohio State Ag. Extension - http://ohioline.osu.edu/hyg-fact/1000/1050.html

Hope this helps.