Can plants live forever?
The answers to these questions often boil down to "what do you mean by live forever?".

You've included vegetative cloning, so I infer that counts as one living organism for your purposes. In that case, the answer is absolutely.

Pando is at least 10 thousand years old and only getting larger. The Cavendish banana is about 150 years old, but produces at least 70 million tons of bananas yearly.

See here for other giant clones. Of particular interest is King's Lomatia, represented as a species by a single, sterile, individual. Fossilized triploid leaves are too old for carbon dating(at least 45 thousand years old), so it's essentially unknown how old it is.

I would be comfortable declaring Pando immortal, since it's way too big to be eaten, too resilient to burn down, and has already survived the middle and end(at least!) of an ice age. That just leaves (ha) disease and basically nothing else as possible threats.