
Not urgent. Climbing ivy is not a parasite. It does not tap into the tree or feed on it, and light growth on a lower trunk is close to harmless. Three real problems arrive later: the vine adds substantial weight and a great deal of wind-catching surface high in a crown that never evolved to carry it; it shades out the tree's own foliage once it spreads through the canopy; and — the one arborists care about most — it hides the trunk, so nobody can see a crack, a cavity, a conk, or an old wound underneath. A tree in a full ivy jacket cannot be properly inspected.
Years, and nothing about the vine itself will drop a limb tomorrow. What shifts is the risk profile in weather: a canopy carrying a full ivy load holds snow and ice it was never built for and catches wind in winter when the tree ought to be bare, so the failure ivy causes shows up in an ice storm rather than on a calm day. The other thing that changes is diagnostic — every season the ivy stays on is another season the trunk goes unexamined, so a defect that should have been caught early keeps growing behind it. Cut the vines this year and the trunk is readable next year.