Hardy Hibiscus: How to Plant, Grow and Care

When to Plant Hardy Hibiscus?

The ideal time to plant Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) and Hibiscus coccineus (Scarlet Rose Mallow or Swamp Hibiscus) is in the spring, after the last frost. For an early start, sow seeds indoors about 12 weeks before the last expected frost.

Hibiscus syriacus (Rose of Sharon) can be planted in either spring or fall, but those planted in fall may not return as reliably the following spring compared to those planted in spring.

Where to Plant Hardy Hibiscus?

Light

Hardy Hibiscus thrive in full sun to light shade. They perform best when they receive ample sunlight, but too much shade can cause the plants to become leggy, with fewer buds and reduced flowering.

Soil

Hardy Hibiscus prefer moist, fertile soils. Hibiscus syriacus (Rose of Sharon) is well-suited to well-drained soils and can tolerate dry conditions and prolonged drought. In contrast, Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) and Hibiscus coccineus (Scarlet Rose Mallow) are adapted to wet, marshy conditions and can handle sites with poor drainage that are too wet for many other plants.

Site

To protect the plants, choose a planting site that is sheltered from strong winds. Hardy Hibiscus, depending on the species, is suitable for USDA Zones 4-9. Not sure about your growing zone? Check here.

These Hibiscus plants add a striking touch to perennial borders, city gardens, coastal areas, and cottage gardens. These plants grow quickly and can be used for foundation plantings, as a backdrop in borders, or as flowering hedges. Dwarf varieties are perfect for patio containers.

How to Plant Hardy Hibiscus?

Plant your Hibiscus so that the stem is level with the soil surface. If needed, add backfill soil to adjust the planting height.

Space plants 2 to 3 feet (60-90 cm) apart.

Water thoroughly after planting and apply mulch to retain moisture, suppress weeds, and protect the roots during winter.

Hibiscus Care

Watering

Water regularly throughout the summer to keep the soil moist.

Fertilizer

Hardy Hibiscus will benefit from fertilization. Feed with a water-soluble or slow-release, balanced fertilizer. If using a slow-release fertilizer, apply it three times a year, in early spring, after the first round of flowers, and in mid-summer.

Ensure that you do not over-fertilize, as this can cause toxicity and kill your hibiscus.

Pruning / Deadheading

• Deadheading: Removing spent flowers from your Hibiscus encourages the plant to produce new blooms throughout the growing season.
• Hardy Hibiscus: Hibiscus moscheutos dies back to the ground in winter. Cut it down to near ground level in late autumn or early spring before new growth starts.
• Rose of Sharon: Hibiscus syriacus requires minimal pruning. Focus on removing diseased, damaged, congested, or crossing branches. If pruning is needed, do it in late winter or early spring when the plant is bare.
• Scarlet Rose Mallow: Hibiscus coccineus is typically cut back after flowering. Remove dried stems to the ground in late winter.

Propagation

• Rose of Sharon (Hibiscus syriacus): Propagate this plant using softwood cuttings in late spring, semi-ripe cuttings in summer, or layering in spring or autumn.
• Hardy Hibiscus (Hibiscus moscheutos): Propagate by seed or division in spring, or by softwood or semi-hardwood cuttings in spring or early summer.
• Scarlet Rose Mallow (Hibiscus coccineus): Propagate this species using seed or stem cuttings.

Common Problems with Hardy Hibiscus

Pests: Hardy Hibiscus may encounter pests like aphids, Japanese beetles, and whiteflies which can damage foliage. 

Fungal Diseases: Conditions such as leaf spot, blight, and rust may develop, especially in overly moist environments. To prevent these issues, ensure proper spacing for good air circulation and avoid overhead watering.

Leaf Drop: In cooler climates or sudden temperature changes, Hardy Hibiscus might experience leaf drop. This is often temporary and should be resolved with stable conditions.

Floppy Growth: When grown in too much shade, Hardy Hibiscus can become leggy and floppy, resulting in reduced flowering. Ensure they receive full sun to light shade for optimal growth.

Poor Blooming: If the plant isn’t blooming well, it may be due to insufficient light, incorrect soil pH, or nutrient deficiencies. Ensure the plant gets enough sunlight and check the soil conditions.

Winter Damage: In severe winters, even Hardy Hibiscus might suffer damage. Apply mulch around the base in late fall to provide insulation against extreme cold.

Frequently Asked Questions

What is the difference between hibiscus and hardy hibiscus?

The term “Hibiscus” generally refers to a broad genus of flowering plants, which includes both tropical and hardy species. Tropical Hibiscus are native to warm regions and thrive in USDA Zones 10-12. Hardy Hibiscus is a subset of Hibiscus refers specifically to species and hybrids that can withstand colder climates, typically hardy in USDA Zones 4-9. They are adapted to survive winter temperatures and often die back to the ground in cold climates, resprouting in spring.

Is hardy hibiscus the same as rose of Sharon?

Hardy Hibiscus commonly refers to species like Hibiscus moscheutos and Hibiscus coccineus, two U.S. native species. These plants are typically large, with dinner plate-sized flowers, and are adapted to colder climates. Although often grouped with Hardy Hibiscus, Rose of Sharon (Hibiscus syriacus) is a different species with more shrub-like growth and smaller, less dramatic blooms. It is also more tolerant of dry conditions and is native to East Asia.