You are asking here and you will get the Freewrite house answer. Yes - you can write it off the cuff. To me, the difference between prose and a poem is that the poem has a certain rhythm to it.

Of course, there are all kinds of set forms like a Haiku, or a Sonnett or, or, or which have very specific requirements. And many poems rhyme.

I didn't use to like poetry because I felt it was so restrictive - so many musts! But then, I came across some modern poets and it felt like storytelling to me and I liked it. So, I say, write it and if you say it is a poem, we will believe you...