HOW TO GROW ROSE MALLOWEnjoy the beauty of the tropics in your garden year after year with Hibiscus moschuetos, a cold-tolerant perennial hibiscus.
If you’re not familiar with rose mallow, get ready to be amazed, especially if you garden in a northern climate. This often overlooked native perennial offers all the exotic floral beauty of tropical hibiscus (Hibiscus rosa-sinensis) but is tough enough to overwinter outdoors in areas as far north as Minnesota.
Like tropical hibiscus, rose mallow boasts huge, vibrantly colored flowers, some growing to the size of dinner plates. But once your hardy hibiscus bursts into bloom, it will continue flowering until the first frost and then return again in spring for a repeat performance. Despite its tolerance for cold weather, rose mallow also loves the heat and grows equally well in balmy southern climates.
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Common rose mallow, swamp mallow, swamp hibiscus, dinner plate hibiscus; also shares the common name hardy hibiscus with Hibiscus syriacus.
3 to 8 feet tall, 2 to 5 feet wide
Fast. New growth is slow to emerge from dormancy in spring, but plants shoot up rapidly once they take off, growing as much as an inch per day.
Mostly native to swampy areas, rose mallow prefers evenly moist, humus-rich soil. If necessary, mulch to help retain moisture.
Midsummer until the first frost. Although the flowers only last a day or two, rose mallow is a prolific rebloomer.
White, pink, red, or bi-colored, often with a contrasting eye.
Broad, triangular, and deeply lobed. Usually medium green, but some cultivars have deep purple, coppery red, or blue-tinged foliage.
What to look for when purchasing rose mallow plants:
When shopping for rose mallow, look for plants labeled as indeterminate, which indicates that the flowers are produced all the way up and down the stems and not just at the tip, like determinate varieties. Indeterminate bloomers, such as those in the Summerific® series from Proven Winners, will produce flowers for months on end, giving you a longer season of interest. Summerific® plants are not prone to setting seed, which can be a big plus if you don’t want your plants to self-sow in the garden.
When to plant:
In spring or fall, as long as there is no danger of frost.
Where to plant:
In full sun (at least 6 hours daily). In hot climates, it may be necessary to provide some afternoon shade to prevent scorching of the foliage. Also provide shelter from strong winds, which can damage the delicate, crepe-papery flowers. Because of rose mallow’s preference for wet soils, it thrives in low spots and wetter areas along streams or ponds. However, it will tolerate a wide range of soil types if kept well-watered.
How to plant:
Start seeds indoors in early spring and then transplant outdoors once the weather warms or purchase potted plants from a nursery. When planting, be sure to give plants plenty of elbow room to accommodate their eventual spread. If necessary, amend sandy or poor soil with compost or other organic matter before putting your plants in the ground.
Because of its colossal blooms, rose mallow makes a bold statement wherever you plant it, so be sure to use it judiciously so it won’t steal the show from the other plants in your garden. It’s best used as a backdrop for sun-loving groundcovers or plants with strappy foliage that will add nice textural contrast to the broad leaves. Get more ideas for good companion plants to grow with rose mallow.
Use in combination with spring bloomers such as creeping phlox or Jacob's Ladder. Since hardy hibiscus are late to emerge, plants like these can carry the workload for the first half of the year.
Water regularly and up to twice a day in hotter weather, especially if growing in a container. Wilting leaves are a sure sign that your plant needs a good soaking. To avoid leaf fungus and other foliar diseases, water during the early morning hours rather than late in the evening.
Once new growth appears in spring, sprinkle a slow-release organic plant food around the root zone and then supplement with a water-soluble plant food in early summer, when the buds begin form, to boost flower production.
When properly planted and cared for, you can get many flowers from one rose mallow plant (shown is Summerific® 'Cranberry Crush'). Photo by: Proven Winners.
When you see new growth begin to emerge in spring, prune back the old woody stems to about 6 inches tall to make way for the new foliage. To stimulate branching and promote a bushier habit, you can prune the tips of the branches in early summer.
Deadheading of spent blooms isn’t necessary unless you want to prevent seedpods from forming.
In colder climates, apply a layer of mulch around your plants after they die back in the fall to provide an extra layer of insulation. While plants are dormant, water only enough to keep the soil moist.
Rose mallow growing in a pot can generally be left outdoors unless temperatures are expected to drop below 20 degrees F for a prolonged period of time. During a cold snap, take precautions by moving the pot to an unheated interior space, such as a garage or garden shed, until the temperatures warm up again.
Diseases and Pests:
Particularly vulnerable to Japanese beetles and sawflies. Leaf fungus can also be a problem but is easy to control by maintaining good air circulation around the plant and by removing diseased leaves.
ROSE MALLOW PICTURES
Summerific® 'Berry Awesome' — Buy now from Proven Winners
Hibiscus moscheutos hybrid
Height/Width: 40 to 48 inches tall, 54 to 60 inches wide
Large ruffled flowers, up to 8 inches across, bloom all over this densely compact shrub from mid-summer to early fall. Chosen as Proven Winners' 2019 Perennial of the Year.
Summerific® 'Cranberry Crush' — Buy now from Proven Winners
H. moscheutos hybrid
Height/Width: 36 to 48 inches tall, 48 to 60 inches wide
A dense, naturally compact shrub. Large flowers are 7 to 8 inchess across and originate from nodes all up the flowering stems, not just at the top like others.
Summerific® 'Holy Grail' — Buy now from Proven Winners
H. moscheutos hybrid
Height/Width: 48 to 54 inches tall, 54 to 60 inches wide
Deep red flowers are set against incredibly dark (nearly black) foliage on this rose mallow. Perfect as a show-stopping mid-to-late-summer focal point.
Summerific® 'French Vanilla' — Buy now from Proven Winners
H. moscheutos hybrid
Height/Width: 42 to 48 inches tall and wide
Plush 8-inch ruffled flowers with striking red throats start out soft yellow when in bud and mellow to creamy white upon opening. Has a graceful, rounded habit.
Summerific® 'Ballet Slippers' — Buy now from Proven Winners
H. moscheutos hybrid
Height/Width: 48 inches tall, 54 to 60 inches wide
White flowers with petals edged in pink look like giant pinwheels rotating around deep-red centers. A prolific bloomer, with flowers packed all along the stems from top to bottom.
Height/Width: 3 to 4 feet tall, 2 to 4 feet wide
A compact rose mallow hybrid featuring coppery red foliage and enormous light-pink flowers (up to 12 inches across) with prominent red centers and red veining.
Height/Width: 4 to 6 feet tall, 2 to 3 feet wide
Striking fine-textured green foliage develops a purple blush in full sun, contrasting beautifully with the vibrant burgundy-red flowers.
‘Blue River II’
Height/Width: 4-5 feet tall, 2-1/2 to 3 feet wide
Pure snow-white flowers are set off by deep green leaves with a tinge of blue. The radiant white blooms look spectacular in a moon garden because of their large, reflective surfaces.