Well in the case of the one in Paul and Jacqui's garden in Ashford...9 foot!
Yes my firstname.lastname@example.org inbox has been filling up with some very tall sunflowers, often accompanied by some very small children.
Here are Phil Hall’s grandchildren Morgan and Brandon in front of theirs in Hedge End that currently stands at just over 3 metres (almost 10 feet).
Paul Amey in Yateley sent in this picture of my his two great nieces and one great nephew, Melissa, Chloe & Ryan Hooton, with a 7 foot 6 sunflower looking down on them.
Lisa sent in this one of 3 year old Jacob Philps and his whoppers.
The tallest was last measured at 10ft 4 but has since grown bigger.
Here's Zachariah Sealey-Adams, aged 4 at his Nanny & Grampy's house in Banbury.
No news of how tall it is but it's clearly quite big.
Donna got in touch to say that her dad Don Simmonds in West End has got three impressive ones, the biggest a ten footer.
Here are Karen Mallet in Lancing’s efforts.
They are her first ever to be grown from seeds and at this point 10 foot 2 is the biggest, with three more to come out.
Ang Climpson has sent in this picture of her dad Dennis next to his 13 footer in Hastings.
Forget the sunflower...what’s that massive leafy thing behind it??
But of course it's not just sunflowers that are pretty massive.
Catriona Lyus from Tunbridge Wells says "My Hollyhocks are growing very tall this year! They are currently measuring 7.5ft tall and my Verbena Bonariensis are a staggering 8ft at the moment".
And here's the proof.