I'm not sure if this completely answers the question, but I've located what I assume is the intended poem.
Rose Leaves
by Henry Austin Dobson
I intended an Ode,
And it turned to a Sonnet.
It began à la mode,
I intended an Ode;
But Rose cross'd the road
In her latest new bonnet; I intended an Ode;
And it turned to a Sonnet.
I can only find it attributed to Dobson, and not Leigh Hunt. Maybe someone else knows more