Rose of sharon ‘Marina’ is a hardy deciduous shrub, popular for its profusion of rich blue, trumpet-shaped flowers that bloom in late summer. Each flower, highlighted with a contrasting crimson center, radiates against lush green foliage. This resilient plant thrives in full sun and well-drained soil, tolerating summer heat with graceful endurance. Rose of sharon ‘Marina’ adds a tropical flair to temperate landscapes, attracting pollinators while being relatively low maintenance.
I. Appearance and Characteristics
Free flowering, Hibiscus syriacus ‘Marina’ (Rose of Sharon), often sold as ‘Blue Satin’, typically grows with an upright habit, up to 6-9 ft. tall (180-270 cm) with a spread of 3-6 ft. (90-180 cm). This is a sterile cultivar that does not produce viable seed.
It is a dense and bushy deciduous shrub noted for its abundant violet blue flowers resembling hollyhock blossoms. Blooming continuously from midsummer to fall, the large deep royal blue to violet-blue flowers, 4 in. across (10 cm), are adorned with dark reddish-purple throats and conspicuous, protruding, creamy-white tubes of stamens. Each flower lasts about one day, but the plant blooms continuously and heavily until late in the season. The foliage of broadly ovate, three-lobed leaves is dark green. A very useful, structural shrub for the back of the border.
II. How to Grow and Care
Sunlight
Rose of sharon ‘Marina’ likes ample sunlight for at least six hours a day. However, direct sunlight should be avoided during high temperatures in summer afternoons. Otherwise, the leaves can easily become sunburned.
Temperature
Most Hibiscus plants are relatively resistant to cold, tolerating temperature as low as -18 ℃, and are also relatively resistant to drought. Chinese hibiscus (Hibiscus rosa-sinensis) and its hybridization varieties thrive in warm environments and generally cannot adapt to temperatures below 0 ℃. Temperatures of no less than 10 ℃ are best in winter for most Hibiscus plants. The optimum temperature for Chinese hibiscus is 16 to 32 ℃, and the species is not resistant to drought.
Watering
Young rose of sharon (Hibiscus syriacus) should be watered often. The soil around the plant should be soaked, preferably in the evening. For adult plants, rainwater is usually sufficient except in the case of continuous drought. The water demand of Chinese hibiscus is more than that of rose of sharon (Hibiscus syriacus) in summer. Potted plants also require more water than plants in gardens.
Swamp rose mallow (Hibiscus moscheutos) requires more water and is resilient in damp conditions; it is better to water it every day in summer as long as soil drainage is ensured. Roselle (Hibiscus sabdariffa) is relatively resistant to drought and should be thoroughly watered when the soil is dry.
Soil
Rose of sharon ‘Marina’ like slightly acidic, moist, well-drained soil with a pH value of 5.5-7. If the soil is sticky and heavy, coarse sands may be added to improve permeability. In the case of slightly alkaline, chalky soil and lime soil, add rotten leaf soil, peat soil, or completely decomposed garden compost along with sulfur fertilizer until the pH value reaches an appropriate range.
Fertilizing
Adult plants do not require frequent fertilization, but flowering plants are best fertilized annually. In early spring, granular or powdery slow-release fertilizer should be mixed into the soil around the aboveground part of the plant, generally 60-70g/m2. Rose of sharon ‘Marina’ prefers potash fertilizer rather than phosphate fertilizer. Newly planted plants may also require additional, quick-acting, liquid fertilizer weekly.
Planting Instructions
The best planting season for rose of sharon ‘Marina’ is during fall while it is still warm. This allows the root to recover in warm soil, encouraging vigorous growth the following year. A location that receives sufficient sunlight and is slightly shaded in the afternoon is best for planting rose of sharon ‘Marina’, depending on the local sunshine projection. All weeds should first be removed before planting, and then a planting pit can be dug. The pit should be at least twice the diameter of the root ball and attached soil, and slightly deeper than the root ball’s height.
For potting, try to choose a dwarf variety and the largest flowerpot possible. The flowerpot should be of sufficient weight and stability, with stone pots preferred. Pot depth should be at least 1.5 times the depth of the root ball. The diameter should be 1/6-1/4 of the height of the adult plant. Place 3 cm of rough stones at the flowerpot bottom for better drainage.
Sort and scatter the root ball, place it in the flowerpot or planting pit, and then gradually backfill and compact the soil. Cut off any diseased, damaged, inward-growing, or crossed branches and other branches that affect the plant’s shape. Water thoroughly and spread a 5 to 7 cm layer of decomposed medium or crushed bark. If the plant is a standard seedling type with a single trunk, insert a stake before planting to support the plant.
Pruning
Rose of sharon ‘Marina’ generally does not require pruning. If desired, however, it should be pruned in early spring. Keep 2-4 buds on each branch grown the previous year and cut off any dead, diseased, or weak branches. For shrub shaping, trunks should be pruned to different heights, creating a sense of levels. For tree shaping, the lateral branches at the lower trunk should be removed and the upper lateral branches should be shortened.
To restore old branches, prune after blooming in fall. Each trunk should be shortened to a height of 30 to 46 cm. Afterward, apply a slow-release fertilizer. In the next growing season, keep 2-4 stronger, new branches on the trunk.
Propagation
Rose of sharon ‘Marina’ can be propagated by shoot cutting. Cut the new shoots with wooden bases and soft tips during the end of summer or early fall at a length of about 10 to 15 cm. Then, cut off the soft stem tip and remove the lower leaves. Cut a 2.5 to 4 cm-long piece of bark longitudinally at the shoot base, dip the shoot in rooting powder, insert it into the culture medium, and water once with a solution of fungicidal drugs.
Afterward, regularly water it, avoid direct sunlight, apply liquid fertilizer once every 2 weeks, and promptly remove any weak cuttings. After the shoot roots, it can be transplanted into a flowerpot as an individual plant.
Transplanting
Rose of sharon ‘Marina’ thrives when transplanted in the invigorating days of early to mid-spring. Choose a sunny, well-drained location for optimal growth. If needed, gently prune roots for better establishment. Transplanting during these periods encourages robust root development.
III. Uses and Benefits
Rose of sharon ‘Marina’ is planted in shrub borders for dramatic summer blooms. It is great flowering shrub for foundation plantings, hedges or screens.
IV. Harvesting and Storage
The single flower of rose of sharon only blooms for a day and then withers. It is best to pick flowers that have just blossomed at sunrise. The fruit harvest time of Roselle is usually in late fall, one month after blooming. At that point, its sepals are fully developed, turning dark purple before the lower leaves start falling. The fruits can be cut off from the stem base with sharp scissors after the morning dew is dry.