Jennifer Schultz Nelson
Extension Educator, Horticulture
If you're looking for a flower that will turn heads and have your friends and neighbors asking "What is THAT?" then consider the hardy hibiscus. With flowers up to twelve inches across, they are certainly a show stopping addition to your garden.
My first encounter with hardy hibiscus was seeing it in our next door neighbor's yard when I was a freshman or sophomore in high school. All of a sudden, what had been an unassuming mass of leaves all summer was covered in giant white flowers with deep red centers. The flowers dwarfed the foliage.
Later that season my neighbor offered me seeds from her plant. Hoping they would grow and look at least a little bit like the plant they came from, I clutched my little baggie of seeds and eagerly awaited the following spring planting season.
The seeds grew easily, and if I remember correctly, I think that little seedling produced flowers in its first year! Successfully going from seed to twelve inch wide flowers made me feel like I was approaching the ranks of being a "real" gardener.
The following year, tragedy struck. My little perennial garden was about a three foot wide border at the north end of the family vegetable garden. When my dad tilled the vegetable garden in the spring there was always a risk to my flowers. He was not a big fan of flowers in a vegetable garden, and routinely tilled the garden just as close as he could get to my flowers. And yes, lots of times he forgot where the flowers were.
Hardy hibiscus is one of the last perennials to leaf out in the spring. Thinking there was nothing planted in the area where my hardy hibiscus was planted, since it had not leafed out yet, my dad tilled it up. I was horrified as I carefully raked through the newly tilled soil, hoping to find the crown of my hardy hibiscus intact and able to be replanted. It was a gardening miracle to find the hibiscus intact, small green leaves just beginning to wake from their winter nap. I replanted the hibiscus and it grew beautifully that year, like nothing unusual had happened. I nicknamed my plant "Timex" because it "took a licking and kept on ticking".
Hardy hibiscus got its name not from surviving my dad's tiller, but from the fact that they are hardy into Zone 4. They are often confused with tropical hibiscus, Hibiscus rosa-sinensis, which are only hardy in frost-free areas.
Confusing matters more is the fact that modern hardy hibiscus is not a single species. Most modern cultivars of hardy hibiscus are interspecific crosses, which means different hibiscus species are crossed to produce a new hybrid cultivar. Two of the commonly used species as parents of interspecific crosses are H. coccineus, a deep red flower also called Texas Star, and H. moscheutos, with white or pink petals and deep red centers.
Modern hardy hibiscus hybrids began with the efforts of plant breeder Robert Darby in the 1950's. He did his plant breeding work in Maryland, so it was fitting that his first hybrid, still grown today was the deep red 'Lord Baltimore'. In 1977 he introduced 'Lady Baltimore', with pink petals and a deep red center.
One of the more unique sources of hardy hibiscus hybrids has to be Fleming Flower Fields of Lincoln, Nebraska. Brothers Jim, Bob and Dave Fleming lived together on the family farm and never married. Instead they dedicated their lives to perennial flower breeding. They released hybrid cultivars of many different flower species, but hibiscus was a favorite of the brothers, the last of whom passed away in 2001--or as their website so cleverly put it "passed into perennial dormancy".
The Fleming brothers' best known hibiscus hybrid is 'Kopper King'. This hybrid has enormous pink-petaled flowers with red centers and unique finely cut, copper colored leaves, giving it landscape interest even when not in flower.
Hardy hibiscus performs best in full sun locations with well-drained soil. Fertilizers are not absolutely necessary for this plant, but if you choose to fertilize, use higher nitrogen fertilizers only until July, so as to not disrupt flower bud formation. After July use fertilizers higher in phosphorus to encourage blooms.
The Fleming Flower Fields website recommends cutting back hardy hibiscus when they reach two feet in height to just one foot. The stress of this cutting back is said to cause them to produce twice as many flowers. It's a bit late to try this on my own hardy hibiscus, but I will keep it in mind for next year.
It is not unusual for hardy hibiscus to die back totally to the ground each winter. They are slow to emerge in the spring. Every year just when I think my gorgeous deep-pink hardy hibiscus 'Sweet Caroline' didn't make it through the winter, I spy a tiny green shoot emerging.
Hardy hibiscus is one of those garden plants that requires relatively little from you, but gives you an enormous amount of beauty and enjoyment in return. I highly recommend them for any perennial garden.