When you remove ivy that has grown up your siding, you're usually left with dark stains and tiny suckers all over the wall. Ivy holds itself in place with these suckers, casting tendrils that grab onto and wedge into every crack or space they can. Ivy suckers are tough and anchor themselves even deeper into wood siding, which is naturally more porous than vinyl or aluminium siding. Removing the suckers is painstaking--and often frustrating--work, but it is possible with the right techniques.
Cut the main stems at the base of the root. This will kill the top part of the ivy plant. Don't simply pull the ivy away from the wall, because doing so can damage the siding and any masonry near it.
Dig out the root or apply a weed killer to the cut surfaces of the stem to kill the roots. If you don't kill or remove the roots completely, new shoots will grow, even from the smaller roots.
Wait until the top growth of the ivy plant dies completely. When the ivy is brown, brittle and withered, you can more easily remove the suckers from the siding.
Scrub off the suckers using a semi-soft brush and warm, soapy water. If you have wood siding, the suckers may seem to embed themselves into the wood, so you'll need to do a lot more scrubbing. You can also use a pressure washer.
Inspect the siding for any damage while you're removing the suckers. Siding that is in good condition should not experience any damage from the ivy suckers, but older or weathered siding may experience some cosmetic marring.
Use a small paint brush to apply the weed killer to the cut stems of the ivy plant. This way, you'll apply the chemical exactly where you need it, without leaching it into the surrounding soil. Use a stiffer wire brush or even a paint scraper to remove ivy suckers from wood siding.
Don't use a pressure washer on vinyl siding. Pressure washing is appropriate only for wood siding when you don't care whether any paint or stain comes off. Don't leave the dead suckers on the siding for more than two or three weeks. If you leave the suckers too long, they'll rot, oxidise and harden. At that point, they'll be impossible to remove without damaging the siding.