Who’s not familiar with rose of Sharon? A staple in older gardens and rural farmsteads, does it still have a place in today’s modern spaces? Yes! Fortunately, thanks to a number of improvements, there’s more to choose from than ever, including dwarf varieties and better flowers.
Rose of Sharon (Hibiscus syriacus or Althaea syriacus) has been gracing American yards and farmsteads for generations. Its very staying power over the years says it all for ease of cultivation, excellent longevity and valued late season color.
The common name with which we’re most familiar is confusing because this plant is actually a mallow in the hibiscus family. Also referred to as “common hibiscus,” Althaea shrub or rose mallow, in America we know it best simply as rose of Sharon.
Unlike some other types of hibiscus, rose of Sharon varieties are fully hardy in zone 6 or colder. All they want is a half day or more of sun, average soil and adequate water during dry spells. It doesn’t get any simpler!
The original species we remember from our youth are vase-shaped, multi-stemmed 6 to 12-foot shrubs bearing single flowers in lavender, pink or white. Individual blooms are five-petaled and hollyhock-like, with a prominent pistil covered in creamy pollen. Often they have a dark eye. They’re known for being tough, resilient and very long-lived.
Today’s hybrids improve on all these qualities, offering semi-doubles and double blooms in fresher colors with much better coverage. In many cases hybrids are healthier, prettier, longer-blooming shrubs all around. Some are even sterile, providing color for weeks without self-seeding.
One of my favorites is Morning Star (but it’s getting hard to find). A semi-double with a particularly attractive flower, white with a partially obscured burgundy eye. That hint of color adds just the right amount of depth and allure. The long-lasting display is very prolific and thankfully sterile.
Here’s another benefit: Being only partly double, its semi-open structure still allows bumblebees to forage (with a little effort), and they sure do love it.
At just five to six feet tall and a yard wide, it is also easy to manage.
I grow Morning Star as a shrub, one in part shade and several as a short hedge in full sun. I look forward to its cheery blizzard of white every August and September. They stay neat and tidy all season, with most spent blossoms falling off cleanly.
Of course there are many other cultivars to choose from, especially in pink and lavender-blue. Here are a few.
Other Cultivars to Consider
One of the best semi-double strains is Chiffon. All are vigorous growers in white, blue or pink, each a little different. White Chiffon is a sterile pure white. Blue Chiffon has great blossom form, quite tall unless pruned lower. Pink Chiffon is a frilly warm pink touched with cerise.
There are dozens of cultivars and you really can’t go wrong with any of them, or with the older varieties for that matter. Do plant at least one single or a semi-double for the pollinators, though. Fully double forms are not accessible to them.
I’ll highlight just three other choices, the first being Oiseau Bleu or Bluebird. It bears elegant single blooms in a cool lavender-blue with a grape eye. (In cool weather it turns almost electric-blue with a magenta eye.) Bluebird gets quite large, up to twelve feet high, but it can be pruned shorter if desired.
Sugar Tip is remarkable not only for its pink carnation-like flowers, but for variegated foliage! A companion plant in a deeper pink, magenta or burgundy foliage would really set it off.
For something smaller in scale, Pollypetite is a pretty pink dwarf that stays just 3 feet tall by 4 feet wide. It’s the perfect size for walkways, patio edges and smaller beds. I haven’t seen it for sale, though.
Planting and Care
Rose of Sharon has to be among the easiest shrubs to grow, even for beginners. It’s not picky about soil, and it will tolerate intense sun and part shade, searing heat, freezing winters, and near-total neglect. Just ensure young plants and transplants get watered regularly the first year or two and during dry spells, and keep them well-mulched.
Pests
A number of insect pests are drawn to rose of Sharon. Japanese beetles can be a real nuisance some years. Buy a green-and-yellow pheromone trap made explicitly for Japanese beetles. I strongly recommend putting up at least one in late May through mid-August. (Your roses will thank you too.) You won’t dissuade all of the (male) beetles to leave your plants for the trap, but you will catch enough to put a significant dent in the population. (If only a few are getting trapped, try a different spot. Make sure the scent lure is fresh, and check the trap every few days.)
Other infestations that occasionally strike include cotton scale, aphids, and “scentless hibiscus plant bugs” — yes, that’s their actual name. Luckily you can control all of these pests with insecticidal soap or fine horticultural oil. Both are organic concentrates you mix with water and apply with a spray applicator. I use a tank sprayer but a spray bottle will work for small infestations. These solutions kill by suffocation. They work great against a wide variety of insect pests. Avoid spraying any bees, of course, and pick a day without a breeze.
I had major cotton scale on my rose of Sharons last year (and a few this year). Just two treatments of horticultural oil about two weeks apart eradicated them. These products don’t contain nasty chemicals and are very garden friendly. You do have to wet the pests directly which means coating both sides of the leaves, so it can be tedious. But the results are well worth it.
Tree or Shrub?
There are two ways to grow rose of Sharon. The first is to simply let it do its thing. Old-fashioned varieties are multi-trunked shrubs eventually reaching anywhere from 8 to 12 feet high and 3 to 6 feet wide. Flowers form mostly on the outer branch tips. Toothed foliage covers the upright stems nearly to the ground, which grow into an upright vase shape.
Newer hybrids are bushier and more spherical, with excellent flowering (and branching) all over the plant. Both shrub types are easy-care, requiring almost no shaping from you.
The second way is to start with a young plant and train it to a single trunk over several years. Side shoots and lower foliage is removed regularly from the lower third of the bush, leaving a single stem. As the stem thickens over several years, a petite tree is created. Top growth can be pruned into a ball or left to cascade gracefully. The result looks like a standard, but isn’t. (Sometimes you can buy specimens already trained or even braided, for a higher price.)
The tree form is prized because it fits into tight spots very easily and the overall size is easier to control. Tightly pruned top growth will also produce larger individual flowers. This style looks wonderful framing an entryway or in formal and urban settings.
Shaping is a matter of personal taste, and whether ones wishes to make the effort. Some people use both forms in the same garden.
Regardless, top pruning (if needed) is best done in late winter, before bud break. You can safetly remove 6 to 12 inches at once. Side branches or wayward stems can be cut anytime.
TREE / SHRUB PRUNING TIP – To thin or reduce branching, prune in midsummer or during active growth. To increase bushiness and stimulate growth, prune in late winter or when dormant.
Multi-trunked forms tend to break in storms more easily that single-trunks, especially mature specimens that get brittle with age. I lost a magnificent Morning Star this way. Of course there’s no guarantee any plant will survive extreme conditions. But splayed and double-trunked specimens are especially vulnerable.
COMPANION IDEAS
Rose of Sharon goes well with just about anything. In a mixed shrub border, it looks fabulous with landscape roses, crape myrtle (Lagerstroemia) or butterfly bush (Buddleia), all of which are similarly sized and in bloom at the same time.
Think about how it will look the rest of the year. I underplant mine with spirea Magic Carpet, whose evolving foliage and early summer flowers add interest when rose of Sharon is out of bloom.
Another trick is to pair it with a color other than green. Try it with ruby, bronze, blue or chartreuse specimens of weigela, ninebark, barberry or juniper. Nestle a few Sharons among the azaleas and rhododendrons to enliven those otherwise boring areas in late summer.
Sharon trees look smart with formal trimmed box, in city pocket gardens and even sidewalk planters. Whether in the garden or a container, you can underplant them with dwarf fountain grasses, short garden phlox, bulbs, creeping eunonymous, juniper, cotoneaster, liriope, dwarf holly, daylilies, anemones and more.
Finally, don’t forget annuals. Try purple celosia, melampodium, sunpatiens, mums or even tall begonias at their base.
So there you have it. I hope I’ve convinced you that Rose of Sharon is easy, versatile, resilient and beautiful. A terrific addition to any garden.
