Billy Rose expounded:

Extremely odd. Every arborist or tree cutter I've ever talked to has
said don't let the ivy climb the trees because it will weaken or kill
them. I have three lots full of trees. Regularly have them trimmed to
let in more light.

Not only does it weaken and kill them, but the ivy morphs into the
adult that bears flowers and fruit, which the birds carry off and
spread. It's an invasive plant throughout its range, any extension
service that says otherwise is doing a disservice to its area.
--
Ann, gardening in Zone 6a
South of Boston, Massachusetts
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