Our region's shrub form of hibiscus has a long and storied history in the garden, a history that starts in ancient Asia, where Hibiscus syriacus, the species we know commonly as Rose of Sharon, is native. While not native in Europe, Rose of Sharon was cultivated there for centuries and is referred to throughout ancient writings, including passages of the Bible. Settlers brought it to the New World, and it soon became a landscape mainstay in colonial America.
It's easy to understand why Rose of Sharon has remained so popular. There are few plants as easy to get established in the landscape or as floriferous and rewarding with so little expenditure of effort. While Rose of Sharon is considered a shrub, it's good to note that it's a rather large, bulky one. At 10 to 12 feet tall and six to 10 feet wide, it will rapidly eat up space in a small yard. But its seductive bloom can easily override gardening logic, especially when the plant is small and loaded with color.
H. syriacus and its three-to-four-inch-wide flowers bloom on new wood. It buds in midsummer and begins to bloom in late July, continuing into September. Rose of Sharon loves full sun but tolerates light shade, and, like its tropical brethren, this Zone 5 plant craves heat. Its leaves tend to be the last of any shrub to emerge, grudgingly peeking out in mid-May in southern New England but not until Memorial Day or beyond in the northern reaches of its range.
H. syriacus is divided into double-flowered and single-flowered varieties, with doubles tending to start their bloom slightly later than singles. Many doubles have been garden mainstays for decades, with flower colors that range from white and pink to red and violet. Some of the best double varieties are 'Ardens,' with its rose-purple flowers; 'Blushing Bride,' with rich pink flowers that fade to white; 'Jeanne D'Arc,' with profuse, pure white flowers; and 'Lucy,' with red flowers on a plant that may be the most vigorous of any double variety.
While the doubles are tried and true, it seems the single-flowering varieties have captured the imagination of today's gar-deners. The singles' earlier bloom time gives them the benefit of the first "oohs and aahs" of the season. Older varieties include 'Aphrodite,' with its dark pink blooms with dark red eye zones; 'Diana,' a pure white, long-blooming selection; 'Bluebird,' a big sky-blue selection with red eyes; 'Minerva,' a dense grower with lavender-violet flowers sporting dark red eyes; and 'Red Heart,' with its big white flowers with bright red centers.
Today, a new generation of singles is moving into the territory of the established singles, with waves of flowers on plants that are denser, more vigorous and slightly longer blooming than the old-timers. Two unique singles, 'Lavender Chiffon' and 'White Chiffon,' break new ground with lavender or pure white flowers with lacy, anemone-like centers. 'Blue Satin' shows off royal-blue flowers with darker eyes on a plant that is far superior to 'Bluebird' for strength. 'Blush Satin' has huge pinkish-white flowers with prominent red centers, while 'Violet Satin' is a flowering maniac with huge, deeply colorful violet-red blooms.
If the shrub form of hibiscus makes you wait for its foliage to show up, the perennial form will have you on the edge of your seat, even into early June, wondering if it has made it through the winter. You can relax, though, since many varieties of perennial hibiscus are tougher than their shrubby relatives, with Zone 4 hardiness that can bring the tropics to even the northernmost garden. Just like in the tropics, they will bring flower size and color that, at times, is so astonishing that you can't help but stare.
Most selections of perennial hibiscus belong to the species H. moscheutos or H. coccineus, both North American natives, or are crosses between these and other less prominent species. Most form dense, wide, rapidly growing bushes in the garden. They love hot sun, heat and moist soil, although they adapt well to drier ground. When they begin to bloom in mid-July, they instantly dominate the garden with their flower size and color and continue to do so into mid-September. Be sure to place perennial hibiscus at the back of the garden and give them some room, because their size will tend to overwhelm any plant in the vicinity.
There are so many great selections of perennial hibiscus that it's hard to list them all. The Disco Belle series has seen long, distinguished service in the garden. These H. moscheutos selections come in shades of white, red and pink, with five-inch diameter flowers covering a dense, Zone 4 bush that is two to three feet tall and three to four feet wide. 'Lord Baltimore' and 'Lady Baltimore' tower over the garden - they're six to seven feet tall and four to five feet wide - with seven-to-10-inch flowers in lush red and ruffled pink, respectively, that are dizzying! These H. coccineus selections are also Zone 4 hardy.
The Luna series is newer to the market and is more like the Disco Belle series, but with wider flowers than Disco on denser plants. 'Luna Blush' (six-to-seven-inch white flowers with red eyes), 'Luna Red' (seven-to-eight-inch dark red flowers) and 'Luna Pink Swirl' (six-to-seven-inch pink flowers with white swirls) put on a display of flower power that is unrivaled among Zone 5 plants.
'Fireball' and 'Kopper King' bring a different show to the garden, with distinct red-tinged foliage that is as outstanding as their blooms. 'Fireball' sports six-to-eight-inch burgundy-red flowers, while 'Kopper King' draws gasps with 12-inch blooms that are pink with deep red eyes. 'Fantasia' may offer the most unique flower color of any perennial hibiscus; it shows off a myriad of nine-to-10-inch lavender flowers with purple-red eyes. All three of these varieties are three to four feet tall and wide, and they're hardy to Zone 4.
