I planted a single Hardy water lily directly into my pond a couple months ago and it's doing great. I want to add more but I don't want them to overtake my pond. Is this a concern if I have a lot of shallower water? Would putting them in pots help to prevent this from happening?

Freg, it depends on the hybrid lily you added. Bill Cody has said that the smaller the leaf, the slower the spread, and that has been my experience as well.

This what I use when I plant lilies in tubs. concrete mixing tub They're cheap, and easy to slide around if fluctuating water level is an issue.

So planting in tubs will help control the spread? My current lillies have about 3 inch leaves.

Planting in containers will prevent spread under most conditions. I did find out that beaver dig up and eat the rhizomes, and also use them to clog drain pipes. If beaver or muskrat "transplant" your lilies, then some could escape, but that would be a rarity. My family of 6 beaver have now been eliminated, but not before really trimming back my lily beds. It appears that they may have decimated my white and yellow lilies while leaving the pinks less disturbed.

I have some small leafed (2-4") lilies I planted which are spreading much, much easier than I had anticipated. Seems they have spread from broken off leaf/stem (dog runs through the shoreline frog hunting). I spotted a pad or two and a few weeks later its firmly rooted over 100' away from the main plant. The nursery lily with larger pads which might be 10" is growing extremely fast has not spread to any other spots.

Plant the varieties that are termed dwarf and small. They spread slowest and grow shallowest usually 2-maybe 4 ft deep. Large spread types of lilies will grow fastest and move into deeper water up 12-15ft deep when water is clear. Examples of dwarf and small varieties:

https://pondmegastore.com/collections/dwarf-and-small-hardy-water-lilies

https://www.gardenia.net/guide/dwarf-and-miniature-hardy-water-lilies

https://www.pondplantsonline.com/co...-hardy-water-lily?variant=32034734473309

Bill thanks for the links!

Is there an ideal time to plant these? Guessing late Spring?

Best time for planting lilies is at time of flowering up until late summer - August so the rhizome has time to establish anchoring roots before winter.

Thank you Bill!

They get eaten quickly in our lake. I have to fence everyone to keep them going. I have 5 or 6 different colors and varieties. None have shown the ability to survive or spread outside of fenced areas. Turtles really butcher them.