Wide single or double flowers, violet-blue, white or pink and often marked with a crimson eye, open in relays all summer, each one replaced within two or three days. Rose of Sharon (Hibiscus syriacus) is a deciduous shrub for hedge, bed or pot: give it full sun and shelter from wind and it flowers on into autumn.
| Name | Hibiscus syriacus |
|---|---|
| Family | Malvaceae (mallow family) |
| Type | shrub |
| Height | 3 to 13 feet (1 to 4 m) |
| Exposure | full sun, part sun |
| Foliage | deciduous |
| Flowering | midsummer to late autumn |
You’ll get magnificent flowers from this plant with proper care. Planting and pruning is easy and it resists diseases well.
All year round, your Hibiscus syriacus shrub must be planted in a soil mix designed for flowering plants, for planting, or any universal soil mix.
Prefer planting in fall or spring if you have purchased the shrub in a pot or a container. Usually, bare-root shrubs can be purchased in garden stores during the planting season. Plant them quickly if this is the case.
It readily propagates through cuttings in spring.
Simply keep cut stems in a vase with water, and plant as soon as a few roots appear.
The plant also bears seeds prolifically, to the point of being invasive in some areas. It’s very common that seeds produce plants and flowers that are different from the parent plants. You’ll be growing new surprises with every batch!
Althea asks very little, but each job has its own moment and its own knack. Here is the whole growing year on one line per task.
| Task | When | What it involves |
|---|---|---|
| Growing in a pot | Repot early to mid-spring, every two years at most | Soil mix for flowering plants, in a container only slightly larger than the last |
| Planting in the ground | Mid-autumn or mid-spring | A sun-bathed spot sheltered from the stronger winds |
| Cuttings | Mid-spring | Stand cut stems in a vase of water and pot up once roots show |
| Seed | Late autumn, as capsules brown | Seedlings rarely match the parent, and self-sowing can become invasive |
| Pruning | Early to mid-spring, as buds swell | Thin out inward-growing branches, then shorten stems by about two-thirds |
Flowers are carried on new growth, so spring pruning costs you nothing in bloom.
Prune your shrub in spring.
Flowers bloom on new growth, so you won’t be losing any blooming.
You can deadhead old blooms if you’re into details, but wilted flowers quickly fall off on their own.
Hold off until the buds start to swell, since althea breaks into leaf late and bare stems can still be perfectly alive.
Hard pruning gives fewer but larger flowers, while a light trim gives many smaller ones.
Cut off the brown seed capsules before they split open.
An old, congested Rose of Sharon tolerates being cut back hard into bare wood, as it resprouts readily from the base.
Cultivars differ mainly in flower colour, in whether the bloom is single or double, and in how big and bushy the shrub becomes. The table below gathers the varieties most often sold in garden centres and mainstream catalogues, to help you match one to your border, hedge or pot.
| Variety | Flower colour | Flower form | Habit | Best use |
|---|---|---|---|---|
| Blue Bird (Oiseau Bleu) | Violet-blue, red eye | Single | Medium, upright | Specimen, mixed border |
| Woodbridge | Deep rose-pink, crimson eye | Single | Medium, upright | Border, informal hedge |
| White Chiffon | Pure white | Anemone-centred | Medium, upright | Pale-themed border |
| Blue Chiffon | Lavender-blue | Anemone-centred | Medium, upright | Mixed border |
| Lavender Chiffon | Soft lilac | Anemone-centred | Medium, upright | Border, light screening |
| Pink Giant | Pink, dark eye | Single, large | Medium, upright | Specimen |
| Purple Pillar | Purple-pink, red eye | Semi-double | Narrow, columnar | Narrow gardens, screening |
| Red Heart | White, bright red eye | Single | Medium, upright | Informal hedge |
| Aphrodite | Rich pink, dark red eye | Single | Medium, spreading | Specimen, hedge |
| Diana | Pure white | Single, very large | Medium, upright | Specimen, white borders |
| Sugar Tip | Light pink, cream-variegated leaves | Double | Compact, bushy | Foliage accent, containers |
| Minerva | Lavender-pink, red eye | Single | Medium, rounded | Border, screening |
| Helene | White, deep red eye | Semi-double | Medium, bushy | Mixed border |
| Hamabo | Pale blush pink, crimson eye | Single | Medium, bushy | Sunny border |
| Duc de Brabant | Deep red-purple | Double | Medium, upright | Border, cut flower effect |
| Lil’ Kim | White, deep red eye | Single | Dwarf, compact | Pots, small beds |
All there is to know about the Hibiscus syriacus
Hibiscus syriacus, also called Althea or more poetically Rose of Sharon, is definitely one of the most beautiful flowering shrubs. Native to Southwest China and Northeast India, Hibiscus syriacus has been a favorite of enlightened gardeners and landscapers for millennia.
Greek botanists in the 1st century thought the plant came from the Syrian region, and, true to botanical practice, the name ‘syriacus’ stuck.
Summer is when it is at its best, with new flowers opening up every two or three days to replace those that die off.
This plant hybridizes very easily with pollen from many plants in the mallow family. Cross-fertilization is often successful. Seeds bear flowers that are often different from those of the mother plant. The upside of this is that there are hundreds of colors and shapes for blooms to choose from!
Its blooming is very generous, in that it is both opulent and constantly renews itself from July to October and even November if the weather stays mild.
Even if this shrub prefers warm climates, several varieties are very hardy and well suited to harsher climates.
Whatever the configuration – hedge, flower bed or stand-alone – Hibiscus syriacus will enchant you with the beauty of its flowers.
If it freezes in your area, it is highly recommended to winterize your plant. Wrap it up with horticultural fleece towards the end of November.
