If you crave a taste of the tropics in your northern climate, try your hand at growing a hardy hibiscus plant full of huge, showy flowers. Native to North America, the oversized flowers feature tissue-thin, ruffled petals in shades of pink, red, magenta, and white. Some varietals produce blooms with dark-colored centers. Hardy hibiscus can be planted in spring when there is no risk of frost. The plants will grow quickly, erupting each summer with blooms the size of dinner plates.
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In addition to adding color to your summer garden, hardy hibiscus blooms attract hummingbirds, dragonflies, and butterflies. While each bloom lasts only a day or two, they are quickly replaced by new blooms. You might be tempted to cut a bouquet, but don't—hibiscus blooms are better-suited in the landscape than being cut and placed in a vase, where they'll last only a day or so.
What Is Hardy Hibiscus?
The term "hardy hibiscus" generally refers to cultivars of Hibiscus moscheutos that are bred to tolerate colder temperatures than most Hibiscus species, most of which are tropical species. These cold-hardy varieties are also known as "perennial hibiscus." Most hardy hibiscus will reliably tolerate temperatures as far north as zone 5, but even zone 4 gardeners may be able to find varieties suitable for their growing conditions.
|Common Name||Hardy hibiscus, rose mallow, swamp rose mallow|
|Botanical Name||Hibiscus moscheutos|
|Plant Type||Herbaceous perennial|
|Mature Size||3–7 ft. tall, 2–4 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Average, organically rich|
|Soil pH||Neutral to slightly acidic|
|Flower Color||White, red, pink, blue|
|Hardiness Zones||4–9 (USDA)|
|Native Area||North America (Missouri)|
Hardy Hibiscus Care
Hardy hibiscus plants are cold-hardy despite bearing large blooms that look at home in the tropics. Although the plants seem woody in summer and function as sub-shrubs in the landscape, their stems die back to the ground in winter, technically classifying them as herbaceous perennials.
Hardy hibiscus plants are surprisingly easy to care for considering their bountiful, delicate blooms—if they receive enough sunlight and water. They do well as container-grown plants, too, allowing you the opportunity to bring the plant indoors for the winter season if you live in a cold climate. Repot container-grown hibiscus into a larger pot every two to three years.
For your hardy hibiscus plant to bloom to its greatest potential, it needs at least six hours a day of full sun. However, if you live in a hot and dry climate, provide your hardy hibiscus occasional relief from the hot afternoon sun—grow other leafy plants nearby to cast a shadow or choose a planting location that is lightly shaded in the afternoon. Indoor hibiscus plants should be situated near a sunny (preferably southwest facing) window—if that doesn't provide your hibiscus with enough light, you can augment with grow lights.
Hardy hibiscus are wetland plants, and therefore are the ideal specimens for moist areas on your property where it might be difficult to grow other plants that don't require as much moisture. Hardy hibiscus also grows well when planted around water features and ponds. Hardy hibiscus plants require organically rich soils—if the soil in your landscape is not rich with organic material, amend the planting area with organic compost before planting.
If you can't locate hardy hibiscus plants in a moist spot in your landscape, make sure to keep the plants adequately watered—but don't overdo it. A hardy hibiscus is typically thirsty and needs a deep watering of at least 1 to 2 inches of water per week and needs to be watered almost everyday. A small plant with fewer leaves needs less water than a large, leafy plant. A good indicator that your plant needs watering is when an inch down into the soil is dry.
Temperature and Humidity
Hibiscus plants flower best in temperatures that range from 65 degrees Fahrenheit to 75 degrees Fahrenheit. Bring plants indoors before temperatures dip to 32 degrees Fahrenheit, but be mindful that low humidity can dry them out quickly. If you bring your hardy hibiscus indoors for the winter, you'll need to mist the leaves daily or place each pot on a pebble tray filled with water. As the water evaporates, the humidity will rise around the plant. A small space humidifier will also raise humidity levels in your home.
Hardy hibiscus plants need plenty of nutrients and regular feeding. Feed your plant with a diluted liquid fertilizer once a week or a slow-release fertilizer three times a year, including early spring, after the first round of blooming, and mid-summer.
Types of Hardy Hibiscus
Some of the most common hardy hibiscus plants vary in size and blooms:
- Hibiscus moscheutos 'Lady Baltimore': This variety is 4 to 5 feet tall and up to 3 feet wide. It features light pink flowers with a red center.
- Hibiscus moscheutos 'Robert Fleming': This compact variety is about 2 to 3 feet tall and wide at maturity. Its huge blooms are a deep, velvety red.
- Hibiscus moscheutos 'Summerific Perfect Storm': This compact and well-branched variety produces dark purple foliage and can grow to be 3 feet tall and 4 feet wide. Its large 7-inch whitish-pink flowers have a red eye.
Because this plant dies to the ground in winter, you can prune it down to the ground in fall or in spring before new growth emerges. The root system will survive the winter, and new growth will emerge from the root system.
Propagating Hardy Hibiscus
The best way to get an exact replica of the parent hardy hibiscus plant is to propagate it with stem cuttings. Propagate with this method in the spring or early summer for best results. Follow these steps:
- Cut a section of new growth or softwood about 3 to 5 inches long, removing any flowers or flower buds from the node area.
- Pour some rooting hormone into a shallow dish, moisten the cut end of the stem, and dip it in the powder.
- Use your finger to create a hole in the moist growing medium, ensuring the hole is wide enough so that the rooting hormone won't rub off when you place the cutting into the hole. Tamp down the soil around the cutting and water well.
- Cover the cutting with a plastic bag, and place it in a warm location with temperatures of 60 degrees Fahrenheit or higher.
- New leaves should appear eight weeks later; when the cutting has developed a root system, repot it into a larger pot. Plant in the ground after the last frost in the spring.
How to Grow Hardy Hibiscus From Seeds
If you do not need a replica of the parent hardy hibiscus plant, grow a new one from seeds. Buy seeds or collect them from the pods that form after the plant has flowered. The plant will produce pods if the flowers were pollinated.
Leave the pods on the plant until they turn brown and crusty because then the seeds are ready to be harvested and sown. Each pod contains between 10 and 20 seeds. The seeds need to be stratified and scarified for best results. Do this by keeping them dry in a protected container outdoors so they can feel normal winter temperatures (stratification). Begin to sow them indoors about six to 12 weeks before the last frost. Or you can sow them directly in the ground after the last frost. Here's how to grow hardy hibiscus from seeds:
- Soak seeds overnight to soften them because they will need to be nicked (called scarification) to allow water in.
- Put seeds in a jar with some gravel and shake well; This method should break the outer coating of the seeds a bit.
- Sow seeds 1/4 inch deep into a seedling pot filled with well-draining seed starting mix.
- Keep pots in full sun or under grow lamps.
- Replant seedlings into larger pots after four to five weeks.
- Harden off seedlings as the last frost approaches. Harden by taking pots outdoors during the day and back inside at night.
If you live with mild temperatures year-round, then your hardy hibiscus will thrive throughout the year, too. But if you live in an area where winter temps dip below freezing, you will need to protect your plants. When overwintering hardy hibiscus that's planted in the ground, wrap it in a heavy cloth (burlap) or tarp. The material will need to be able to stand up to freezing, frosty conditions. If your hardy hibiscus is potted outdoors, you can bring it indoors but it will need to stay in temperatures of about 55 degrees Fahrenheit plus about three to four hours of direct full sun a day to survive.
Common Pests & Plant Diseases
The usual gang of garden pests loves to hang out on the underside of hardy hibiscus leaves and cause holes in the foliage. These insects include aphids, Japanese beetles, mealybugs, sawfly larvae, spider mites, thrips, and whiteflies.
Hardy hibiscus plants also tend to be bothered by various fungal diseases such as leaf spot, blight, and rust, which often develop when the plant is subject to excessively moist conditions. To avoid such problems, when you water your plant, apply the water to the base of the plant so you don't introduce excess moisture onto the foliage. Proper spacing between your hardy hibiscus and other plants is key as well—adequate airflow will help prevent the development of fungal diseases. If all else fails, you can periodically treat affected plants with a fungicide.
What's the difference between a hardy and a tropical hibiscus plant?
The two types of hibiscus are hardy and tropical. Hardy hibiscus typically survives the winters outdoors though it dies back to the ground on its own while dormant in the cold weather. Tropical hibiscus needs to be brought indoors for the winter.
Can hardy hibiscus grow in partial shade?
The plant can be grown in partial shade, but it probably won't bloom very well. It needs sun to create blooms. If the plant is in the ground and can't be moved, see if you can remove any barriers preventing sunlight from bathing the plant. Even one or two hours a day can help increase the blooms.
Can hardy hibiscus be grown indoors as a houseplant?
Many tropical hibiscus plants can grow indoors as houseplants, but it's best to leave hardy hibiscus outdoors. One reason is that it can grow out of control indoors, and if it's not placed in full sunlight, it won't even produce blooms.