Many posts ago I wrote about the world's largest waterlilies, the Victorias http://troybmarden.blogspot.com/2008/03/aquatic-giants.html, whose giant floating leaves may reach 8 feet in diameter in a well grown plant and whose night-time flowers approach nearly a foot in diameter. At the far opposite end of the spectrum is the diminutive Nymphaea 'Helvola' or 'Pygmaea Helvola' which, with floating pads only 2 inches in diameter and tiny yellow, star-shaped flowers only an inch-and-a-half across, can be easily kept in a tabletop water garden where it will grow and bloom just as beautifully as its larger pond grown cousins.
I became a fan of 'Helvola' when I was a college intern at Longwood Gardens in Kennett Square, PA where it held court in the water gardens along with its hardy and tropical cousins from around the world, growing just as well in a large pond as it will in a small tabletop bowl.
Growing requirements are the same as for all waterlilies: Full sun (minimum 6 hours per day) and, once growth commences in spring, a monthly feeding of a good waterlily fertilizer. This usually comes in a hard pellet that can be put underwater without dissolving and be pushed right down into the soil at the roots of the plant where it will slowly release its nutrients over a month's time. 'Helvola', being miniature, needs only about 3-4 inches of water over its crown.
Remember that the ultimate spread of a waterlily's leaves over the surface of the water is directly related to how deep in the water it sits and how long the leaf petioles must grow in order for the pads to float on the surface of the water. So, if you want to keep 'Helvola' at its smallest size, keep it as shallow as possible so that the petioles only have to grow a few inches in order for the leaves to float. In deeper water (not more than 10-12 inches, please, since it's a mini), in a pond, for instance, 'Helvola' may spread across the water's surface to a size of 3 feet, but the pads and blooms will remain miniature.
Did I mention that 'Helvola' is hardy? That's right! This diminutive creature is hardy to Zone 5 and in winter, can be dropped a little deeper in the pond (below ice level) or it can actually be removed from the water and stored in its container in a garage or storage room as long as it doesn't freeze solid during cold weather. In spring, simply repot with fresh soil, place back in the water garden and in a few weeks, Voila!, new growth and blooms for the rest of the summer. If you're growing it as a tabletop specimen in a small container, simply pour out the water and remove the entire container to a cold, but non-freezing location for the winter, refilling and placing back outdoors once spring weather arrives.
So if you're looking for a beautiful waterlily that will perform beautifully both in the water garden or in a container, look up little 'Helvola'. It's sure to impress!