Swamp mallow (Hibiscus moscheutos), also known as rose mallow hibiscus or swamp hibiscus, is a shrubby, moisture loving plant in the hibiscus family that provides big, showy flowers from midsummer to autumn. The plant performs well along pond edges or other damp areas. This stunning, low-maintenance plant is available in a range of colors, including pink, peach, white, red, lavender, and bi-color varieties.
I. Appearance and Characteristics
Hibiscus moscheutos, the rose mallow, swamp rose-mallow, crimsoneyed rosemallow, or eastern rosemallow, is a species of flowering plant in the family Malvaceae. It is a cold-hardy perennial wetland plant that can grow in large colonies. The hirsute leaves are of variable morphology, but are commonly deltoidal in shape with up to three lobes. It is found in wetlands and along the riverine systems of the eastern United States from Texas to the Atlantic states, its territory extending northward to southern Ontario.
Numerous forms exist in nature. It is a tall plant, with a height of 1.5–2.5 meters (4.9–8.2 ft) and flowers up to 20 centimeters (7.9 in) across. Petal colors range from pure white through various pinks to deep red, and most have an eye of deep maroon. Taxonomic consensus is lacking for the nomenclature of the multiple subspecies. The flowers are borne apically, whereas the related Hibiscus laevis carries bud and bloom along the stem.
It is a larval host for the common checkered skipper, the gray hairstreak, the Io moth, and the pearly wood nymph.
II. How to Grow and Care
Sunlight
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.
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.
Watering
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.
Soil
Swamp rose mallow like slightly acidic, moist, well-drained soil with a pH value of 5.5-7. If the soil is sticky and heavy, coarse sands may be added to improve permeability. In the case of slightly alkaline, chalky soil and lime soil, add rotten leaf soil, peat soil, or completely decomposed garden compost along with sulfur fertilizer until the pH value reaches an appropriate range.
Fertilizing
Adult plants do not require frequent fertilization, but flowering plants are best fertilized annually. In early spring, granular or powdery slow-release fertilizer should be mixed into the soil around the aboveground part of the plant, generally 60-70g/m2. Swamp rose mallow prefers potash fertilizer rather than phosphate fertilizer. Newly planted plants may also require additional, quick-acting, liquid fertilizer weekly.
Planting Instructions
The best planting season for swamp rose mallow is during fall while it is still warm. This allows the root to recover in warm soil, encouraging vigorous growth the following year. A location that receives sufficient sunlight and is slightly shaded in the afternoon is best for planting swamp rose mallow, depending on the local sunshine projection. All weeds should first be removed before planting, and then a planting pit can be dug. The pit should be at least twice the diameter of the root ball and attached soil, and slightly deeper than the root ball’s height.
For potting, try to choose a dwarf variety and the largest flowerpot possible. The flowerpot should be of sufficient weight and stability, with stone pots preferred. Pot depth should be at least 1.5 times the depth of the root ball. The diameter should be 1/6-1/4 of the height of the adult plant. Place 3 cm of rough stones at the flowerpot bottom for better drainage.
Sort and scatter the root ball, place it in the flowerpot or planting pit, and then gradually backfill and compact the soil. Cut off any diseased, damaged, inward-growing, or crossed branches and other branches that affect the plant’s shape. Water thoroughly and spread a 5 to 7 cm layer of decomposed medium or crushed bark. If the plant is a standard seedling type with a single trunk, insert a stake before planting to support the plant.
Pruning
Swamp rose mallow generally does not require pruning. If desired, however, it should be pruned in early spring. Keep 2-4 buds on each branch grown the previous year and cut off any dead, diseased, or weak branches. For shrub shaping, trunks should be pruned to different heights, creating a sense of levels. For tree shaping, the lateral branches at the lower trunk should be removed and the upper lateral branches should be shortened.
To restore old branches, prune after blooming in fall. Each trunk should be shortened to a height of 30 to 46 cm. Afterward, apply a slow-release fertilizer. In the next growing season, keep 2-4 stronger, new branches on the trunk.
Propagation
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 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.
Overwintering
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.
Pests and Diseases
III. Uses and Benefits
- Ornamental uses
Swamp rose mallow (Hibiscus moscheutos) has lots to offer to gardeners and is a popular choice for its showy flowers and robust and vigorous growth. Since it grows tall and isn’t tolerant of high winds this plant is well-suited to sheltered placements in beds and wall side borders. It makes a bright addition to several garden styles such as informal, cottage, city, and courtyard gardens. This bright plant is very rewarding when combined with cardinal flowers or swamp milkweed.
- Medicinal uses
The leaves and roots are known to contain mucilage. Tea from boiled leaves has been used to relieve cough, sore throat, and digestive inflammation. These medicinal attributes of the tea have been used to treat dysentery, lung ailments, and urinary infections. An infusion of dried stalks has been used to treat bladder infections. Hibiscus moscheutos flowers have also been used externally to reduce swelling and pain from bruises and insect stings.
- Culinary uses
The edible parts of the plant include its leaf buds and young leaves, flowers, immature seed pods (which can be prepared as okra), seeds, and roots.
IV. Harvesting and Storage
The single flower of rose of sharon only blooms for a day and then withers. It is best to pick flowers that have just blossomed at sunrise. The fruit harvest time of Roselle is usually in late fall, one month after blooming. At that point, its sepals are fully developed, turning dark purple before the lower leaves start falling. The fruits can be cut off from the stem base with sharp scissors after the morning dew is dry.
