You can grow an invasive plant but you have to realize that precautions must be made to ensure the spread is limited to your garden. In a large pond, it is easy enough to contain the yellow flag Iris (Iris pseudacorus) in a large pot. I have grown it 2 years now in my large pond in the backyard. This spring it had to be transplanted to a larger pot and so far has a few gorgeous blooms!It bloomed and I was excited because I love Iris and this yellow is stunning in my pond. I do nothing with it. No fertilizing, no special soils, and no special pot. I used my hard clay soil to cover the roots and used smaller 2″ sized river rock to fill the pot. It survived in zone 7 with a winter low of 0 (for a week long period). It is a hardy plant that will spread like wildfire if you are not careful where you plant it.
The yellow Flag Iris is zoned for 3-8 and is in the Iris family. It blooms the first week in May in zone 7 and add a week or two in higher zones. This plants colonizes marshy and wet areas and can easily take over in a few short summers. It must be contained in large pots or some sort of barrier if you not keeping this in a contained pond. I do not recommend putting this in a lake or stream bed unless you are certain you can cut off the dead flowers before they seed and each spring dig up and remove any new growth that has spread the year before. This is labeled a noxious weed and even outlawed in a few states such as Connecticut and New Hampshire. Do not get me wrong, this is a beautiful flower but sometimes with beauty comes danger. There is no real fragrance but with this beautiful flower, who cares.
It also has nice flat leaves that gives visual interest to my pond about 10 months out of the year. This pond beauty provides roots for the goldfish to nibble on too. I would never plant it in the ground nor would I let it take over my pond and next year I may divide into 2 pots. Putting it in a pot works so I am content just having one pot in the pond to enjoy.
As with any plant you wish to grow, check out what it is and how it grows!
Creating. Inspiring. Gardening without the rules!
2015 copyrighted material C Renee Fuller
A link to read more: http://plants.ifas.ufl.edu/node/205