I like this poll but it might be better if there were an image beside each option and a link to an observation. Think it is possible to do both of these but then might become too awkward to view on screen. One reason for wanting a photo is to remind me what each of the species are (as I don't recognise all of these scientific names), this could be checked more thoroughly with the link to the observation.
One other little thing, growing wild in which country, presumably UK?
I also think this is a good poll as it gets away from 'favourite' and shows that other things are possible. Suspect 'what is your favourite' might still be the most common type of poll but finding other options such as this one would be good.