How to Grow Swamp Hibiscus

A Swamp Hibiscus Flower close up in a marsh area

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There are over 200 hibiscus species, and the swamp hibiscus (Hibiscus coccineus) is one of the more unusual and larger varieties. The plant features a unique and beautiful pinwheel-like flower and is vigorous and hardy when grown in the right conditions.

Plant it for best results in early spring after the last frost. With strong woody stems, it can grow over 6 feet tall and up to 4 feet wide. The deep-red and showy five-petalled flowers add a wonderful splash of color to moist garden sites throughout the summer. When it isn't in flower, with its deep-green, thin, and pointed leaves, it can sometimes be mistaken for the hemp plant (Cannabis sativa).

Botanical Name Hibiscus coccineus
Common Name Swamp Hibiscus, scarlet rosemallow, Texas star hibiscus, water hibiscus
Plant Type Herbaceous perennial
Mature Size Over 6 ft. tall, 4 ft. wide
Sun Exposure Full sun, partial shade
Soil Type Tolerates a variety
Soil pH Tolerates a variety
Bloom Time July to September
Flower Color Bright red
Hardiness Zones 6-9 (USDA)
Native Area Southeastern United States

Swamp Hibiscus Care

As you might guess from the name, this plant thrives in sunny, humid, and moist conditions. It's a great choice for planting around a pond, placing in the shallow parts of a pond that are less than 4 inches deep, or next to a stream. Because of its height, it also works well at the back of a perennial border or along a courtyard wall.

They can grow to be over 6 feet tall and may need staking, depending on their height and position. They bloom continuously, however, blooms may last only a day or two until the next burst. The plant also attracts butterflies, hummingbirds, and bees.

It's considered herbaceous to semi-woody and it will die back in the winter before producing fresh growth in the spring.

Light

Swamp hibiscus does best in full sun or partial shade. It can survive in shadier positions, but this usually means the stems will grow overly long and thin, and it will be more prone to collapsing. The blooms that appear aren't likely to be as impressive either.

Soil

This plant usually does well in sandy, loamy, or clay soils. Unlike a lot of other plant species, it can cope with wet soils with medium drainage.

If you live in a drier region, mulching can help the soil to retain much-needed moisture.

Water

The key to success with the swamp hibiscus is to ensure that it's kept moist during the growing season. From spring right through to fall, it will need regular watering.

Although it will only need very limited watering in the winter, it's still best not to let the soil dry out completely.

Temperature and Humidity

This plant prefers hot and humid summers. If you live in a more temperate region, making sure it has a good layer of mulch during the winter will help promote new growth the following season.

Even with mulch, this plant isn't suited to areas that are prone to harsh freezing winter conditions.

Swamp hibiscus can be susceptible to windburn. For this reason, and because of its height, positioning it in a sheltered position is recommended.

Fertilizer

Monthly applications of a slow-release, balanced, and diluted fertilizer during the growing season can be beneficial. More frequent feedings in the spring may help the plant's growth.

Pruning

To keep the height of your swamp hibiscus in check, cutting the stems back towards the end of the winter can encourage healthy new growth.

These plants are fast growers and will reach a decent height again the following season.

Propagating Swamp Hibiscus

Propagating swamp hibiscus from cuttings is easy. Look for a plant with five or more stems coming out of the ground for your cutting.

  1. Take a 6-inch cutting from a healthy plant in the spring.
  2. Dip the cutting in rooting hormone.
  3. Press the cutting 3 inches into a container filled with peat moss.
  4. Keep it moist and out of direct sunlight either indoors or outdoors.
  5. When new leaves start to appear, the cutting can be transplanted to its permanent position.

How to Grow Swamp Hibiscus From Seeds

Swamp hibiscus grows well from seeds. If you're collecting seeds from your existing plants, wait until the seed pods at the base of the flowers turn from green to brown. The seeds within can be removed from the pods and stored until the early spring.

  1. Scrape seeds with sandpaper or a nail file so they will germinate faster.
  2. Soak in warm water for a minimum of an hour to soften.
  3. Sow into moist potting soil.
  4. The seedlings will do well in a sunny position.
  5. Keep soil moist.
  6. Germination should take about two weeks.
  7. Transplant the seedlings to their permanent position after the last spring frosts are passed.

Potting and Repotting Swamp Hibiscus

Swamp hibiscus does well in pots. If mixing in a large container, use it as the center showpiece. Place pots outdoors or even in shallow areas of ponds. Since this plant needs consistent moisture, opt for good quality potting soil. The plant will not bloom in dry soil.

Overwintering

In cooler regions, swamp hibiscus may survive outdoors over winter with a good cover of winter mulch. Limit watering the plant during cool months. The plant does not need to be taken indoors for the winter.

Common Pests & Diseases

Although this is a hardy plant, pests such as aphids can sometimes be an issue. Sometimes it can be enough to spray cold water on the leaves to remove the insects. Insecticidal soaps can also be effective.

Plants with woody stems, like the swamp hibiscus, can sometimes be prone to a fungal disease known as rust. Orange spots, similar to the color of rust, can begin to appear on the leaves.

These sections should be removed by pruning. If the problem isn't cleared up by winter, cutting the stems right back to the ground will eliminate the issue. New and fungal-free growth should appear the following season.