Aquatic Plants - invasive

Yellow-Flag Iris (Iris pseudacorus) on Sep 2, 2020

Submitter does not have a specimen
EDRR Status: Local expert notified

Description of specimen

My friends have a couple of koi ponds in their backyard that have been taken over by a plant. The triangular seeds and yellow flowers led to the suspicion of yellow flag. Regardless of what it is, they want to get rid of it, and we're mostly interested in advice on removal and proper disposal