From our perspective as water lilies, the most critical factor determining our survival and happiness is water temperature. This is the core distinction between us, Tropical water lilies, and our Hardy cousins. We Tropicals are true sun-worshippers. Our roots and rhizomes thrive in water that is consistently above 70°F (21°C). We simply cannot tolerate cold. If the water temperature drops and stays below 65°F (18°C), our growth stalls, our leaves yellow, and we will perish if left in the cold. We are native to frost-free regions and have no natural defense against freezing. In contrast, Hardy water lilies are built for resilience. Their rhizomes can survive frozen in the ice at the bottom of a pond, as long as the pond is deep enough not to freeze solid. They patiently wait out the winter, ready to send up new leaves when the water warms in the spring, even if it's still quite cool.
Our flowering habits are another key difference, one that directly impacts your enjoyment. We Tropical water lilies are known for our spectacular, often fragrant, flowers that rise high above the water surface on sturdy stems. More importantly, we are divided into "day-bloomers" and "night-bloomers." Day-bloomers open our flowers with the morning sun and close them in the late afternoon. Night-bloomers, however, open our blossoms as the sun sets and keep them open until mid-morning, offering a magical evening and early-morning display. Hardy water lilies, without exception, are day-bloomers. Their flowers typically float on the water's surface rather than standing proudly above it. While many are beautifully shaped and colored, they lack the dramatic elevation and the unique night-time performance that we Tropicals provide.
If you are seeking the most vibrant and unusual colors, we Tropical water lilies are the artists of the family. Our genetic lineage allows for brilliant blues, deep purples, and vibrant violets—colors that are simply not found in the Hardy water lily gene pool. Hardy varieties excel in shades of white, pink, red, and yellow. Furthermore, our foliage can be just as dramatic. Many of us Tropicals have leaves with striking, serrated edges or beautiful mottling, adding visual interest even when we are not in bloom. Hardy water lily leaves are typically rounded and smooth-edged, presenting a more classic water lily appearance.
Our growth patterns reflect our climatic needs. We Tropicals are vigorous growers during the heat of summer. We love long, hot days and will spread across the water's surface relatively quickly when conditions are ideal. However, our season has a definitive end. As autumn approaches and daylight wanes, we begin to slow down. In most parts of the US, we cannot stay in the pond over winter. You must lift our tubers from the water and store them indoors in a cool, moist medium until the following spring. Hardy water lilies, on the other hand, are a "plant once and forget" option in terms of annual upkeep. Once established, they return year after year, spreading gradually. Their growth is most robust in late spring and early summer, and they can handle cooler autumn temperatures far better than we can.
For us plants, the right choice depends entirely on the length and intensity of your warm season. If you live in USDA zones 9-11, where ponds never freeze, we Tropical water lilies can be treated as perennials. We will thrive year-round. In zones 8 and below, you must be prepared for the annual task of overwintering us indoors. If you enjoy that ritual and crave our specific beauty, we are worth the effort. For gardeners in colder climates (zones 3-7), or for those who prefer a low-maintenance pond, Hardy water lilies are the logical and reliable choice. They will provide beautiful blooms from late spring to early fall and faithfully return each year with minimal intervention, gracefully enduring the cold winters that would be fatal to us.
