If you’re looking for summer flower power, look no further than hardy hibiscus.
This plant has it all:
* Awesome summer-long flower show.
* Flowers the size of dinner plates.
* Hardiness from Florida to Canada.
* Adaptability to a wide range of soils.
* Fast growth.
* It’s a native.
* It’s even resistant to deer browsing.
It’s the kind of crop growers like to produce because it’s so fast. It’s a plant retailers like to sell because it almost jumps off the shelves when in flower. And it’s a plant gardeners love to grow because it’s foolproof, tough as nails and reliable.
In fact, this is the kind of plant that any budding gardener can grow successfully, giving them confidence to move on and try other species. What’s not to like?
Hibiscus moscheutos and other native species are parents of the cultivated hardy hibiscus, also known as perennial hibiscus or rose mallow. A cousin of okra and cotton, hardy hibiscus is also closely related to tropical hibiscus (H. rosa-sinensis), confederate rose (H. mutabilis), and rose-of-Sharon (H. syriacus).
Unlike its woodier relatives, hardy hibiscus is a herbaceous perennial producing multiple canelike shoots that emerge in late spring, flower in summer and die back with autumn frost.
Hardy hibiscus requires the long days of summer to initiate flowers. Buds form in leaf axils near branch tips and open into the exotic-looking flowers typical of hibiscus, each with five petals surrounding a prominent pistil.
Flowers last just one day, but so many buds form that the plant appears perpetually in flower throughout summer and fall until frost.
Easy to produce
Hardy hibiscus is on the ever-growing list of “crossover” crops produced by greenhouse growers and traditional outdoor nursery growers. Finished plants can be produced from seed, plugs or cuttings in eight to 14 weeks, depending on liner size, growing conditions, time of year and cultivar.
Standard production procedures will suffice, with only high light and high temperatures needed for fast growth. Long days are required for flower bud development.
Although hibiscus is considered a heavy feeder, frequency of fertilization matters more than amount. Over-fertilized plants will grow too large and not flower well, whereas nutrient-deficient leaves will turn yellow.
Uniform soil moisture is necessary, too. Plants allowed to wilt respond with leaf yellowing and leaf drop (reducing plant quality) and produce fewer flower buds.
Keep plants jammed pot tight until canopies of neighboring plants touch, then space to reduce stretch. This allows the development of bushy, compact plants.
Some growers use plant growth regulators on hardy hibiscus. But these products -- and pinching or pruning -- are less important on newer, self-branching cultivars.
Packs a punch
Hardy hibiscus is one of the most gratifying plants a gardener can grow. Few other perennials provide as much bang for the buck in terms of flower size, length of flowering and ease of care.
Hardy hibiscus grows best with full sun in rich, moist soil but tolerates even the poorest, sandiest soil if mulched and watered once in a while.
Flowering is promoted by plentiful rain and sunshine. No matter how much and how often you irrigate a landscape, nothing beats good rain when it comes to stimulating flowering.
Hardy hibiscus is cold hardy from USDA Hardiness Zone 9-4. Plant emergence and subsequent flowering begins in late spring in the lower South and occurs progressively later moving north, with flowering in late summer in the northern United States and Canada.
As with many perennials, some hardy hibiscus won’t return after winter dormancy, especially some of the newer, more refined cultivars.
Still, most plants return year after year, and hardy hibiscus gets better with time. Older plants tend to emerge sooner in spring, grow larger, flower sooner and produce larger flowers than young plants.
Hardy hibiscus is fairly pest resistant. While an array of minor pests can attack plants, the most devastating pest is the larvae of hibiscus sawfly (Atomacera decepta). This pale-green caterpillarlike larvae is gregarious, meaning several often feed on the same leaf or plant. It can quickly defoliate entire plants.
Great cultivars
Dozens of cultivars have been developed in recent years, supplanting older selections such as ‘Disco Belle Mix.’ Newer cultivars produce spectacular flowers up to 12 inches across on smaller, more compact plants.
Unfortunately, in my experience, these compact types lack vigor and don’t overwinter as reliably as larger types. Other new hardy hibiscus are being developed with burgundy foliage and new flower patterns.
New flower colors are on the horizon, evidenced by the bright-yellow flowers of ‘Cole’s Gold.’
I’ve been observing performance of more than 20 hardy hibiscus cultivars at the
‘Blue River II’ is an older cultivar with pure-white flowers averaging 10 inches in diameter. If that’s not impressive enough, this cultivar flowers an average of 20 weeks in north Florida.
‘Moy Grande’ was developed by Ying Doon Moy at
Unlike most other cultivars, the rose-pink flower petals of ‘Moy Grande’ don’t overlap. Flowering lasts about 13 weeks.
‘Turn of the Century’ flowers have white petals fading to dark pink, giving an overall pinwheel look to the flower. Though flowers are just 6 1/2 inches in diameter, the plant flowers for 18 weeks.
‘Fireball’ is one of the patented Fleming Hybrids, developed by Fleming Flower Fields in Lincoln, Neb. It has bright-burgundy flowers on upright stems with burgundy-tinged leaves. ‘Fireball’ is one of my favorites, flowering for 17 weeks with blossoms more than 8 inches in diameter.
Luna Red is one of a new series of dwarf, seed-propagated hardy hibiscus. True to their marketing, plants grew just 2 feet tall and produced flowers 8 1/2 inches in diameter for 15 weeks.
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- Gary W. Knox
Gary W. Knox is professor of environmental horticulture, University of Florida/IFAS North Florida Research and Education Center in Quincy, (850) 875-7100; gwknox@ufl.edu.