I've found that mine does best if placed in standing water. Such as an oversized plant tray or similar. Or if you have a fish pond you can sit it in the shallow end as long as the pot is only half submerged. (You will need to occasionally dump the tray and add fresh water when you see mosquito larvae swimming around). Mine gets taken out of constant water for winter time and it does seem to decline some but in spring I put it back in constant "wet feet" conditions and it really takes off.
Hope this works for you too. :)