Is the halfing leaf that Gandalf from lord of the rings smokes really marijuana?

First, it’s halfling leaf – because the hobbits are also called halflings (being very short).

Second, dropping eaves comes from eavesdropping. Samwise was saying (in his odd manner) that he hadn’t been listening in on the conversation. It has nothing to do with drugs at all.

Third, yes, some do think that Gandalf’s leaf (or some of it) was a psychoactive drug of some kind. Perhaps like marijuana, perhaps not.

It’s nothing more than tobacco, which Tolkien clearly states in the novels. The movies seem to implicate that it may have other effects, like when Saruman basically calls Gandalf a stoner. But in the novels anyway, it’s basically tobacco. There are different variations of pipeweed, but the effect is pretty much the same in all smoked plants.

Let’s hope so

On a side note: smoking tobacco can stunt your growth, which may explain why Hobbits are so small.

Party pooping nerd; they were short long before they took up pipeweed. :p

It’s tobacco. Plain and simple. That’s basically Tolkien injecting his own personal traits into his writings, as he was an avid pipe smoker.