I had a look around and found the following snippet of info:
After blooming, these aquatic plants produce seeds which sink to the bottom of the aquarium and quickly form sprouts. Aponogetons anchor themselves to the substrate. Aponogetons bloom after their summer season of approximately 4 to 6 months. After this stage, Aponogetons enter a dormant stage; aquarium; on live aquarium plants such as Aponogetons, the leaves will fall off, and no additional growth will occur for approximately 3-4 months.
Hope that gives you a rough idea.