Perennial Hibiscus: Bridging the Gap Between Summer and Fall

I discovered perennial hibiscus almost two decades ago when I spotted Lady Baltimore’s enormous pink blooms from across the parking lot of a local home improvement store. I wasn’t looking for her, she just found me as most plants do. That happens a lot. At the time, I knew nothing about perennial hibiscus (Hibiscus moscheutos) other than I had to have this tropical looking beauty in my garden. She met her end that next spring when I assumed she was dead and dug her out, only to discover hibiscus is late to rise and often doesn’t show signs of life until well into May here in my zone 5 garden. Oops. Perennial hibiscus resumes growth in the spring when soil temperatures reach 70 degrees F and is hardy in zones 4-9. For gardeners in colder climates, this might mean that your plant doesn’t come to life until July!

I’ve since developed quite a fondness for the big-bloomed beauty, successfully growing several varieties in my small garden to great effect. While some find the enormous flowers, up to 12″ in diameter, garish and the growth habit quite rangy, I appreciate their ability to bridge the often boring lull between summer and fall, much like rose of Sharon, another member of the hibiscus family. When 85 mph winds hit our area last week, many of my plants including the dahlias, sunflowers and rudbeckia were mowed down. With the exception of one branch on a Evening Rose hibiscus from Proven Winners, all the hibiscus came through unscathed, producing a plethora of buds that should continue to put on a show for the rest of August and into September if I’m lucky.

Size Matters

At five feet tall, Lady Baltimore was destined to be huge and far too big for my small garden. Some of our native hibiscus top out at a whopping eight feet tall. When you consider that many of the older cultivars were more plant than flower, it’s hard to relinquish valuable garden space to a plant that can’t pull it’s weight. After all, it’s about the flowers. With that in mind, breeders have created plants for gardens of all sizes, many of which sport dissected foliage in shades of green, purple and chartreuse on plants that bloom continuously for six to eight weeks. If only the flowers lasted longer. Their enormous blooms open for only a day before fizzling out. Perhaps the only downside of perennial hibiscus is the gooey tissue paper-like appearance of the flowers as they decline. Nothing a little deadheading can’t manage, though.

Hibiscus for Wet Sites

The downspout on the southwest corner of the house feeds into a rain barrel that overflows in heavy storms. The run-over thoroughly saturates the area around it and stays wet for some time due to the heavy clay soil, making the location a prime candidate for a water-loving plant like hibiscus. Our native hibiscus, or rose mallow, grows wild along streams and ponds so the surest way to kill one is to withhold water. Being so close to the patio where we spend most of our time in the summer meant the space needed something dramatic that could camouflage the rain barrel too. Summer Storm hibiscus checked all those boxes.

If You Grow Hibiscus

Because they arrive fashionably late to the spring party, hibiscus require a little patience. And once conditions are right and the soil is warm, watch out. They quickly make up for lost time. I like to leave the stems intact through the winter to remind me where they are in the beds. Then I cut them back in mid-late spring and give them a few inches of compost around the base. Some of the taller ones, like Summer Storm, get cut back by half when new growth reaches about 12 inches. Doing so controls the size and forces the plant to develop denser branching and more flower buds.

All that flowering requires a significant amount of energy so I keep my hibiscus fueled with an organic fertilizer. My go-to is Drammatic K Fish and Kelp fertilizer applied weekly to the foliage and soil. One tip: apply early in the morning and certainly not when company is expected. The fish smell can be unpleasant and lasts for several hours until it’s abosorbed. When my dog Stella was alive, fertilizing time was the highlight of her week. I stop fertilizing after July to prevent the plants from forming new growth that’s easily damaged by frost.

Hibiscus are among the easiest plants to grow and a great way to add a bit of drama to the inevitable lull between summer and fall. Perhaps the only downfall is their appeal to Japanese beetles, which are easily managed with a dish of soapy water held beneath the plants. A gentle shake of the branch causes the beetles to release and drop to a sudsy death.

Do you grow this bodacious beauty?