Water Hibiscus Growing, Facts, Care & Benefits (Hibiscus coccineus)


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A vibrant water hibiscus with bright red petals
Water hibiscus. Photo by Michael Wolf [CC BY-SA]
Water hibiscus, also known as scarlet rosemallow and swamp hibiscus, belongs to the mallow family (Malvaceae) and the genus hibiscus, which also contains okra. Native to the riverbanks of the southeastern United States, water hibiscus is a popular garden and pond plant throughout the world, particularly in temperate regions.

They prefer marshes, bogs, and swamps growing quite hardily in even brackish, turbid waters that would kill many other plants. This combined with their striking 5-merous white or vibrant scarlet flowers make them a pond plant that is held in high esteem.

Facts, Benefits & Uses of Water Hibiscus (Scarlet rosemallow)

The striking, highly visible flowers and pollen parts (pistils and stamens) draw in hummingbirds, butterflies, and many other pollinators. Flowering occurs throughout the summer, with each flower living for approximately a day.

hibiscus coccineus with white flower near a pond
White flower hibiscus. Photo by Jim Evans [CC BY-SA]

In addition, their hardiness is largely due to their ability to filter water and fix excess nutrients like nitrogen that may be present in the water into a form that is usable to other plants. This makes the area not only cleaner and more livable for the water hibiscus itself, but also for other plants and organisms, such as fish, that live nearby in the water.

In fact, some ecological reconstruction companies utilize scarlet rosemallow to help rebuild native wetlands to mimic natural functions, such as water filtration.

Historically, hibiscus of all species have been harvested for their flowers, which are then dried and used in flavorful teas. Due to their bitter taste, the dried flowers are often paired with cinnamon, orange peels, ginger, or other such flavors that help to curb sour or bitter flavors. The leaves and flowers can also reportedly be used fresh in salads, or boiled as greens. While there isn’t much research to back up these claims, hibiscus coccineus is not known to be toxic to humans, domesticated animals, or wildlife.

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Water Hibiscus Fact Sheet:
PLANT TYPE
Herbaceous semiaquatic perennial
HARDINESS ZONES
USDA 7-11
LIGHT REQUIREMENTS
Full sun to partial shade
BLOOM COLOR
Deep red/sometimes white
BLOOM PERIOD
June to September (summer)
MAXIMUM GROWTH
Height up to 182 cm (72 in), spread up to 60 cm (24 in)
PLANTING DEPTH
7.5-13 cm (3-5in)
WATER QUALITY
pH 5.6-7.5

Water Hibiscus Growth, Hardiness & Climate

beautiful red water hibiscus growing on the edge of a pond with other semi-tropical vegetation
Photo by Tatiana Gerus from Brisbane, Australia [CC BY]

Water hibiscus is incredibly hardy and, in the right conditions, a fast grower. It can reach 6 feet (sometimes more) and a spread of approximately two feet in a single year of growth, particularly in its native subtropical home, Florida.

In regions like the northern U.S. and the U.K., growth is limited to around March or April through September or October, so maximum size may not be reached. Blooming typically occurs from June through September, with a single plant producing dozens of blooms, each of which only last a day.

Temperate zones are ideal for hibiscus coccineus – zones 8 and above. Below zone 8 is alright, so long as they receive ample water and are either cut back or brought indoors for the winter. Full sun is preferred, but swamp hibiscus will tolerate some shade. If there’s too much shade, you’ll notice the plant becoming “leggy” and putting out much more lateral growth to try to reach the sun, and not many flowers.


How to Plant Water Hibiscus In Ponds

Large, green, lobed maple-like leaves of water hibiscus
Large green leaves of water hibiscus.

The plant’s crown (the area where the roots and stem meet) should be planted about an inch below ground. Depending on your plant’s size upon purchase, including roots this could mean a total planting depth of 3 to 5 inches. If planting in water, try placing an inch or two of gravel substrate or aquatic soil and placing the roots in the substrate to help anchor the plant in place.

Alternatively, you can plant water hibiscus in pots in shallow areas of the pond. Do not plant in deeper than four inches of water, as more than this could drown the plant or stunt growth. They’re truly not picky about soil, and grow just fine in clay, sand, silt, loam, and mucky boggy soils.

If planting multiple water hibiscus, be sure to space them approximately 3 feet apart to allow for proper growth. If planting from seed, seeds can simply be pressed gently into the dirt after the last frost has passed and watered enough to keep the soil consistently moist, or planted near the pond’s edge where the ground is naturally more damp. A thin layer of mulch can be placed over top of seeds and young, just planted hibiscus to help keep the soil moist, protect them from weeds, and encourage proper drainage.


How to Care For & Maintain Water Hibiscus

A mature hibiscus coccineus with a red flower and green buds
Photo by Eran Finkle from Israel [CC BY]

Water hibiscus requires minimal care; so long as its feet are kept moist and it’s kept in a relatively warm, sunny, and frost-free environment, scarlet rosemallow will be happy. The top branches can be pruned or pinched to encourage lateral rather than vertical growth.

If planted in an area with soil that isn’t naturally kept moist, water hibiscus will need to be watered about every two to three days, providing two inches of water per week. This amount should be adjusted depending on rain, drought, dryness of the air, etc. Most water hibiscus flowers only live for approximately one day, so you’ll want to clean these out of your pond as needed to maintain healthy water quality and prevent nutrient overloading.


How to Winter Water Hibiscus In Ponds

A water hibiscus bud that will bloom in a few days

Water hibiscus is not winter hardy, making it an annual plant in northern climes and a perennial in its native southern range. Once frost hits, swamp hibiscus will die.

To prevent this, you can transplant it to a warm indoor area, harvest its seeds in the late summer and fall to plant the following spring, or trim the stem down to just below soil level and cover with several inches of thick mulch to help insulate it through the winter for resprouting the following year.

Hibiscus coccineus could be considered to be a somewhat pricey plant to purchase year after year, typically ranging around the $20 mark


Is Water Hibiscus Toxic, Poisonous or Invasive?

scarlet rosemallow in the process of blooming near a pond
Photo by Krzysztof Ziarnek, Kenraiz [CC BY-SA]

Though its native range is the southern United States, scarlet rosemallow is not known to overtake areas and as such is not considered to be invasive. Nevertheless, never plant water hibiscus in natural areas or allow it to spread outside of your garden or pond as it could disrupt native ecosystems.

Additionally, water hibiscus is not known to be toxic to people, wildlife, or domesticated animals such as dogs, cats, fish, or horses. However, some other species of hibiscus are quite toxic, such as Rose of Sharon (Hibiscus syriacus), causing nausea, vomiting, diarrhea, and loss of appetite if ingested. As such, be absolutely certain that the plant you’re buying is actually hibiscus coccineus.


Is Water Hibiscus Plant Edible? Will Fish Eat it?

Pond fish are not likely to show much interest in water hibiscus. Some fish, like bottom feeding koi, may nibble at the roots, and more opportunistic feeders like goldfish may try sampling flowers that fall in the pond. However, hibiscus coccineus is not known to be toxic to fish and so shouldn’t hurt them. Nevertheless, do clean out any dropped foliage on a regular basis to keep pond water clean.


Where to Buy Water Hibiscus & Seeds? (UK & US)

Due to its beautiful flowers and hardy nature, water hibiscus is relatively widely sold. You can find it at many plant nurseries, online retailers, and aquarium or pond retailers. A quick online search revealed that this plant goes out of stock somewhat often, so you may need to order in advance or be willing to have a backorder.

We recommend purchasing the plant before spring and allowing it to adjust to its new home in a pot before transplanting it outdoors in or near your pond. Waiting until spring to buy it might mean that you won’t get your plants right away.

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