@aleema….to answer your question the wall was not completely stripped clean of ivy due to the expense to remove all the 'roots' left behind seen in the pic on the surface of the wall. In the pic above the brown markings are actual dead roots left behind from removing the live green ivy . The brown markings is not a stain, they are dried roots and they will be there for years if they are not totally removed from the wall or resurfaced.
Of course all the above techniques are helpful. It's not clear what type of wall the ivy roots in above pic are attached to. By guesstimating …maybe concrete of some type?
In my experience if ivy roots are as thick as shown in the above pic and if they are on brick, cinderblock or concrete wall the best most efficient way to remove all the dry brown existing roots in the pic is by hiring a sand blasting service. If the roots are on wood check with a sandblast service for estimates and replacement finishes. They can adjust the pressure according to requirements needed to remove all the roots. Then refinish wall if necessary and or prime and repaint with concrete paint or stain.
Or you can refinish the wall by using concrete stucco made with concrete and heavy sand mix to cover the wall and roots then paint. A professional will help guide your choices.
Always rinse wall well and allow concrete mixture to dry 48-82 hours before priming and painting with finished product.
Unfortunately ivy roots are very difficult to remove from any surface an estimate for removal would be a good start. Good Luck.
