They get taller. Mine are two years old now, and got to about 3 ft. or so. AND multiplied really well. Last year (year after planting out) they were shorter, and not as plentiful or floriferous. It'll be interesting to see if they gain any height next year.

On the other hand, if they get damaged they will shorten. I had one group of them that got tunneled under by moles, and whacked with a weedeater prematurely last summer. This resulted in a sad picture of decline this summer, with one solitary triumphant bloom on about a 5 inch stalk! I had thought I would have to replace them all this year, but missed the post-Easter sales. They're tougher than I thought.

Good luck!
- robinia

I have been planting my Easter lilies each year, and they
have grown in height. The tallest one this year was 30
inches and newer ones were shorties, I am sure they will
be taller next year. Good luck on yours.

Pretty! love the leaf ball too.

They smell so good. I just love them but mine never returned after I planted them.....