Looks pretty doesn't it? And it is as pretty as many irises one might choose to plant in the garden. Don't! This is the common yellow flag that loves water and wet sites. It spreads by rhizomes, but I found out to my dismay that it also spreads by seed carried on the wind. A friend gave me several yellow flags to plant around my pond.  They didn't do too much, but one day I  found this indestructible…