If you crave a taste of the tropics in your northern climate, try your hand at growing a hardy hibiscus plant. Native to eastern North America, they produce oversized flowers (often compared to the size of dinner plates) and are a great way to add a bit of color to your garden. While each bloom lives only a day or two, they are quickly replaced by newcomers.
Hardy hibiscus can be planted in spring or fall, as long as any risk of frost has passed. The plants will grow quickly, erupting each summer with showy flowers that feature tissue-thin, ruffled petals in blues, pinks, reds, and whites. You may be tempted to pick yourself a bouquet, but you should refrain—hibiscus blooms are better-suited to the landscape than to being cut and placed in a vase, where they'll last only a day or so.
|Botanical Name||Hibiscus moscheutos|
|Common Name||Hardy hibiscus, rose mallow, swamp mallow|
|Plant Type||Herbaceous perennial|
|Mature Size||3–7 ft. tall, 2–3 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Moist, wet|
|Soil pH||Neutral to acidic|
|Flower Color||White, red, pink, blue|
|Hardiness Zones||5–9 (USDA)|
|Native Area||North America|
Hardy Hibiscus Care
Hardy hibiscus plants are cold-hardy despite bearing large blooms that call to mind the tropics. Although the plants seem woody in summer and function as sub-shrubs in the landscape, their stems do die back to the ground in winter, technically making them herbaceous perennials.
Hardy hibiscus plants are surprisingly easy to care for considering their bountiful, delicate blooms—as long as you grant them enough light and water, they will be pretty happy. They make for great container plants as well, allowing you the opportunity to bring the plant indoors for the winter season if you live in an especially harsh climate. Your hibiscus should be moved to a bigger 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 zone you should provide your hardy hibiscus occasional relief from the bright afternoon sun—grow other leafy plants nearby to cast a shadow, or choose a planting location that gets afternoon shade. Indoor hibiscus plants should be situated near a sunny (preferably southwest facing) window—if that doesn't provide your plant with enough light, you can augment with artificial lighting.
Hardy hibiscus are wetland plants, and therefore are the ideal specimens for soggy areas that can't foster other plant life, or for planting around water features and ponds. Hardy hibiscus plants also like organically rich soils—if the mixture in your landscape is lacking in nutrients, amend it with a fair amount of organic compost before planting your hibiscus.
If you are not planting hardy hibiscus plants in an already wet spot in your landscape, make sure they are adequately watered—but don't overdo it. A small plant with fewer leaves needs less water than a large, leafy plant. In warm weather, you'll need to water your hibiscus plant daily; In the winter, water it only when the soil is dry to the touch.
Temperature and Humidity
Hibiscus plants flower best in temperatures that range from 60 degrees Fahrenheit to 90 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 tray with a layer of gravel underneath. Add water up to the top of the gravel—as it evaporates, the humidity will rise around the plants. A small space humidifier can also help.
Growing hibiscus plants need plenty of nutrients. Feed your plant with a diluted liquid fertilizer once a week or a slow-release fertilizer four times a year: early spring; after the first round of blooming; mid-summer; and early winter.
Hardy Hibiscus Varieties
There are a few different cultivars of hardy hibiscus, most of which vary in size and bloom appearance. Some of the most common varietals include:
- Hibiscus moscheutos 'Lady Baltimore': This varietal is 4 to 5 feet tall and up to 3 feet wide. It features light pink flowers with a deep, rich pink center.
- Hibiscus moscheutos 'Robert Fleming': This hardy hibiscus varietal is around 3 feet tall and 4 feet wide at maturity. It blooms with flowers that are deep, velvety red, and extremely ruffled.
- Hibiscus moscheutos 'Summerific Perfect Storm': This varietal grows to be around 3 feet tall and 5 feet wide, with light pink flowers and a deep fuchsia center.
Pruning Hardy Hibiscus
Since this perennial dies back to ground level in winter, you can prune it down to the ground in fall. As alive as the branches of your hardy hibiscus may seem in fall, they will die in winter. However, the root system will live on and new branches will spring out of the ground the following year.
Propagating Hardy Hibiscus
The best way to propagate hardy hibiscus is through stem cuttings. In spring or early summer, cut a section of new growth or softwood about 4 to 6 inches long, removing any flowers or flower buds from the node area. Pour a little 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 mix, ensuring it's wide enough that the rooting hormone won't rub off when you place the cutting in 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 that boasts temperatures of 60 degrees Fahrenheit or higher. New leaves should appear eight weeks later; once the cutting is rooted you can move it to a larger pot.
Common Pests and Diseases
Hardy hibiscus plants have a tendency to deal with 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, make sure to water the plant at the base of the stem so you don't introduce excess moisture into 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 treat affected plants with a fungicide periodically.