It can indicate ageing or some aspect that has existed for some time – thus the ivy growing.
Also it can show an old world charm or beauty. People sometimes dream of flowers and ivy growing and mingling together – which probably suggests the beauty of ageing, or the mixture of old and new, and even the passing of time.
Poison ivy: Poison thoughts or feelings that can cling and cause hurt. Or something that you need to avoid or be aware of.
Useful Questions and Hints:
What do I feel about the ivy in the dream – is it passage of time, an old age beauty or to do with graveyards?
Have I ever been the victim of poison ivy?
Do I feel age creeping up on me?