Tall upright plants are needed by dragonfly and damselfly larvae to climb up to exit the pond and emerge as adults.
Our recent late Summer sun has meant we have seen adults flying and mating later than usual. Just before the chill of Autumn starts.
Tall plants like Pontederia and Typha both make real foliage statements in the pond in the latter part of the season and produce flower or seed heads for visual interest at this time of year. They are also upright plants for the larvae to hang onto to mate above the water.
The Pontederia are also good for the bees as pollinators - the bees were all over the blue flowers of Pontederia cordata last week and they were so busy and moving so fast that it was hard to get a photo. Bees love the late flower of the Pontederia cordata as they try and fuel up before winter.