Hardy Hibiscus: How to Plant, Grow and Care

When to Plant Hardy Hibiscus?

• The best time to plant Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) and Hibiscus coccineus (Scarlet Rose Mallow or Swamp Hibiscus) in the garden is in the spring after the last frost date.
• To get a jump on the season, seeds can be sown indoors 12 weeks before the last spring frost.
• Hibiscus syriacus (Rose of Sharon) can be planted in the garden in spring or fall. However, if planted in the fall, it might not return as reliably the next spring as one planted earlier in the year.

Where to Plant Hardy Hibiscus?

• Hardy Hibiscus perform well in USDA Zones 4-9, depending on species. Not sure about your growing zone? Check here.
• Hardy Hibiscus are easily grown in full sun to light shade in moist, fertile soils. In too much shade, your Hardy Hibiscus may get floppy, with a lower bud count and reduced flowering performance.
• Hibiscus syriacus (Rose of Sharon) is well-adapted to dry climates and to prolonged drought and requires well-drained soil. Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) and Hibiscus coccineus (Scarlet Rose Mallow or Swamp Hibiscus) are 2 wetland species that can grow in marshy conditions. They tolerate sites with poor drainage that are too wet for other plants.
• Select a planting site that is sheltered from strong winds.
• Hardy Hibiscus add an exotic touch to perennial borders, city gardens, coastal gardens, or cottage gardens. They create colorful combinations in the garden with other late seasons’ shrubs or perennials. Quick to grow and fill a space, they are great for foundation plantings, at the back of the border, or as a flowering hedge. Dwarf Hibiscus varieties are well-suited for patio containers.

How to Plant Hardy Hibiscus?

• Set your Hibiscus in the planting hole so that the stem is just at the soil surface. If necessary, add some backfill soil to the bottom of the hole to achieve proper planting height.
• Hibiscus species that die back each year can be spaced 2 to 3 feet apart (60-90 cm).
• Water well around the plant after planting.
• Spread mulch around the plant to keep moisture in and weeds out. This will also provide winter protection for the roots.

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 3 times a year, in early spring, after the first round of flowers, and in mid-summer.
• Make sure not to over-fertilize as this can cause toxicity and kill your Hibiscus.

Pruning / Deadheading

• Deadheading Hibiscus flowers will promote new blooms.
• Hardy Hibiscus flower on new wood (this year’s growth).
• Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) dies to the ground in winter. Cut down to near ground level in late autumn or in spring before new growth emerges
• Hibiscus syriacus (Rose of Sharon) requires little pruning. Remove diseased, damaged, congested or crossing shoots. If pruning is necessary, prune in late winter or early spring when the branches are bare.
• Hibiscus coccineus (Scarlet Rose Mallow or Swamp Hibiscus) is usually cut back after flowering, removing the dried stems to the ground in late winter.

Propagating

• Hibiscus syriacus (Rose of Sharon) can be propagated by softwood cuttings in late spring, by semi-ripe cuttings in summer, or by layering in spring or autumn.
• Hibiscus moscheutos (Hardy Hibiscus or Rose Mallow) can be propagated by seed or by division in spring, or by softwood or semi-hardwood cuttings in the spring or early summer.
• Hibiscus coccineus (Scarlet Rose Mallow or Swamp Hibiscus) can be propagated by seed or stem cuttings.

Pest and Diseases

• Hibiscus are not bothered by many pests or diseases.
• Keep an eye out for aphids or Japanese beetles may feed on the foliage.
• Various fungal diseases such as leaf spot, blight, and rust, may develop when the plant is subject to excessively moist conditions.