Althea ‘Red Heart’, a distinctive cultivar of the Rose of Sharon (Hibiscus syriacus), is cherished for its unique floral display. This popular deciduous shrub offers striking visual appeal with its crisp white petals contrasted by a deep red center. It adds late-season color to various garden settings when many other plants have finished blooming, making it an adaptable and beautiful choice for gardeners.
Understanding Althea ‘Red Heart’
The botanical name for this plant is Hibiscus syriacus ‘Red Heart’. This cultivar reaches a mature height of 8 to 12 feet with a spread of 6 to 10 feet, forming an upright, vase-shaped growth habit. Its foliage consists of medium green, three-lobed leaves. Its single, pure white flowers, each adorned with a prominent crimson or maroon eye, create a striking “red heart” effect. Blooms appear profusely from mid-summer through early fall.
Planting Your Althea ‘Red Heart’
Selecting an appropriate planting site is key for Althea ‘Red Heart’. This plant thrives in full sun, which encourages the most abundant flowering. While it tolerates partial shade, too little sun may result in fewer blooms. The shrub adapts to a range of soil types but performs best in well-draining, loamy soil with a neutral to slightly acidic pH. Avoid heavy, compacted clay or excessively sandy soils to ensure proper root development.
To plant, dig a hole twice as wide as the root ball and just as deep. Ensure the top of the root ball is level with or slightly above the surrounding soil surface. Gently loosen any circling roots before placing the plant in the hole. Backfill with the excavated soil, tamping lightly to remove large air pockets. After planting, water thoroughly to settle the soil around the roots. Plant in spring or fall.
Ongoing Care for Althea ‘Red Heart’
Watering is important for Althea ‘Red Heart’, especially during establishment. Newly planted shrubs need consistent moisture; water deeply two to three times per week during dry spells. Once mature, this shrub is drought tolerant and requires less frequent watering, though supplemental irrigation during prolonged dry periods maintains vigor and bloom production. Avoid overwatering to prevent root issues.
Fertilization for Althea ‘Red Heart’ is optional, as they are not heavy feeders. To promote vigorous growth and blooming, or if soil nutrients are low, apply a balanced, slow-release granular fertilizer in early spring. Follow product instructions carefully to avoid over-fertilization. A layer of organic mulch, such as wood chips or shredded bark, around the base helps conserve soil moisture, regulate soil temperature, and suppress weed growth.
Pruning Althea ‘Red Heart’ helps maintain shape, control size, and encourage flowering. The best time to prune is late winter or early spring, before new growth begins. Remove any dead, damaged, or crossing branches to improve air circulation. Shape by selectively cutting back branches to an outward-facing bud. Since Rose of Sharon blooms on new wood, pruning at this time will not reduce the current season’s flower display and promotes more robust flowering.
Troubleshooting Common Issues
Althea ‘Red Heart’ is generally resilient, but can encounter issues. Pests like aphids may cluster on new growth, causing leaves to curl or distort. A strong spray of water can dislodge them, or insecticidal soap can be applied for significant infestations. Japanese beetles can feed on foliage during summer; hand-picking them off the plant is effective control.
Leaf spot can appear as dark spots on leaves, especially during wet conditions. Good air circulation through proper spacing and pruning helps prevent its spread. Powdery mildew, a white, powdery coating on leaves, can be managed by improving air flow and, in severe cases, applying a fungicide. Yellowing leaves can indicate either overwatering (leading to root problems) or underwatering (causing stress); adjusting the watering schedule is usually the solution. A lack of blooms might be due to insufficient sunlight or incorrect pruning practices.