Rose-of-Sharon or Shrub Althea

(Malvaceae - Mallow Family)

Form

• medium-sized ornamental shrub (can also be limbed up into small tree form)
• maturing at about 8' tall by 4' wide
• upright vased growth habit, often becoming arching with age if never pruned
• medium growth rate

Culture

• full sun to partial shade
• prefers moist, well-drained soils supplemented with organic matter in full sun, but is very adaptable to various soils, soil pHs, soil compaction, drought, heavy pruning, and pollution (and is therefore urban tolerant)
• propagated primarily by rooted stem cuttings, but also by seeds
• Mallow Family, with a few minor leaf disease and pest problems; however, old shrubs can develop trunk cankers that may eventually prove fatal to the plant
• abundantly available, primarily in container form but also in ball and burlap form

Foliage

• medium green, alternate, broadly ovate, palmately veined, 3" long leaves have three distinct lobes with sparsely dentate to crenate margins
• chartreuse fall color is poor

Flowers

• solid colors of white, red, purple, mauve, violet, or blue, or bicolors with a different colored throat, depending upon cultivar
• continuous blooms often occur from July through September, and usually close at night
• the 4" wide, single or double-flowering, large-petaled, very showy flowers adorn the plant throughout the Summer

Fruits

• green to brown, ornamentally unattrative five-valved dehiscent capsules are persistent throughout much of the Winter on older cultivars; most modern cultivars are virtually fruitless
• if fruit capsules are present, they will shatter over the course of the dormant season and spread their easily germinating seeds around the base of the parent plant, forming colonies with time if in naturalized or neglected areas

Twigs

• thin and gray, white-lenticeled, with raised leaf scars and small buds
• stems and branches do not branch very much unless pruned, resulting in many long, straight stems that originate from about 0.5' to 1.5' above the ground that give rise to the overal vased shape

Trunk

• white-gray and relatively smooth, branching very near to the ground unless limbed up into tree form

ID Summary

• a narrow vased-shaped to arching growth habit, many long, straight, relatively unbranched, light gray stems, large solitary single or double flowers that bloom all Summer long, and ovate, shallowly-lobed, alternate leaves are four distinctive traits of this ornamental shrub

USAGE

Function

• specimen, foundation, entranceway, row, or border shrub, or planted as a formal or informal hedge
• occasionally limbed up into small tree form

Texture

• medium texture in foliage and when bare
• average density in foliage and when bare

Assets

• showy flowers bloom throughout the entire Summer
• vase-shaped growth habit
• urban tolerant (especially to heat, humidity, drought, and poor soils)
• relatively rapid establishment

Liabilities

• spent flowers will close up and shrivel, but take several days to abscise from the plant
• with maturity, flexible plant stems become weighted under the load of prolific Summer flowers, and bend over halfway to the ground
• older cultivars that set heavy seed crops can self-sow to form a weedy colony of young shrubs
• with advanced age, trunks may develop cankers that cause individual branches to die, followed by decline and death of the entire plant
• poor fall color

Habitat

• zones 5 to 8
• native to China and India

SELECTIONS

Alternates

• shrubs that flower in Summer (Caryopteris x clandonensis, Clethra alnifolia, Hydrangea species, Itea virginica, Phildelphus species, etc.) or that flower all Summer-long (Buddleia davidii)
• vase-shaped shrubs (Hamamelis x intermedia, Viburnum plicatum tomentosum)

Variants

• Hibiscus syriacus 'Aphrodite' - pink-mauve single flowers having a dark magenta eye
• Hibiscus syriacus 'Ardens' - mauve-purple double-flowering form
• Hibiscus syriacus 'Bluebird' - blue-lavender single flowers having a dark magenta eye
• Hibiscus syriacus 'Diana' - profuse blooming triploid, having pure white single flowers that remain open at night, and set few if any fruit
• Hibiscus syriacus 'Minerva' - triploid, with lavender-mauve single flowers, each having a red eye
• Hibiscus syriacus 'Red Heart' - white single flowers, each having a scarlet eye

NOTES

Translation

• Hibiscus is the Greek name for Mallow.
• syriacus translates as "of Syria," where it was once thought to be native to.

Purpose

• Rose-of-Sharon is a shrub with a vased growth habit, noted for its very showy Summer-long bloom period.

Summary

• Hibiscus syriacus is a shrub with large showy flowers (in single or double flowering form, with solid colors or bicolors) that blooms all Summer long and has a distinctive vase-shaped growth habit.