Tips for Growing Althea
Rose of Sharon will help
bring a bit of tropical beauty to more temperate climates. The blooms that
arrive later in the summer will help revive your garden after the flurry of
spring flowers.
Latin name: Hibiscus
syriacus
Common Names: Rose of
Sharon, Althea, hardy hibiscus
USDA Hardiness Zones: Zones
5-8
Size & Shape of Rose
of Sharon: Rose of Sharon grows to approximately 8-12' tall and 6' wide, with a
vase shape.
Exposure: It is best to grow Rose of Sharon in full
sun, though it can tolerate up to part shade.
Foliage/ Flowers/Fruit
of Rose of Sharon:
Don't be surprised if
the leaves arrive after most of your other plants, as they start producing the
leaves late in spring. Leaves are 2-4" long, often with 3 lobes, and
jagged edges.
The flowers are
2-5" wide, in shades of white, pink, red, blue, purple, and violet. There
is often a different spot of color in the middle of the throat.
Close relatives include Cotton. Okra. Mallow. Marsh mallow (marshmellow). Cotton Boll pictured, Left.
Fruit: capsule
Additional Rose of
Sharon Facts:
Rose of Sharon can be
VERY invasive due to the numerous seeds produced in the capsules. Snip them off
before they open. This causes many to re-bloom!
Choose one
of the newer cultivars that are genetic hybrids - the triploids. These produce
few (if any) seed capsules.
Cultivars from the U.S. National Arboretum include:
·
'Aphrodite'
·
'Diana'
·
'Helene'
·
'Minerva'
2 faves are 'Blue Angel' and 'White Angel'
The blossoms are edible*. (*Colorado State Cooperative Extension Service)
In the UK and Australia,
Rose of Sharon refers to Hypericum
calycinum, which Americans know as St John's Wort.
Rose of Sharon Design
Tips:
Leaves appear late in spring and
the blooms do not show until late summer or early fall, so best used in a border, rather than as a specimen plant.
Rose of Sharon is
somewhat tolerant of drought conditions.
Hummingbird magnet.
Rose of Sharon Growing
Tips:
Rose of Sharon grows
best in moist, well drained soil that contains lots of organic matter, though
happily it is able to tolerate a wide variety of soils.
In the cooler zones
(where the temperatures fall below -10F in winter), be sure to mulch around the
plant well during the winter season.
With hot summers, Rose of Sharon will thrive, actually preferring the heat, and will increase numbers of blooms.
Propagation is by
cuttings and seeds.
Maintenance/Pruning:
Though it is naturally a
multi-stemmed shrub, Rose of Sharon can be trained to have a single trunk,
looking more like a tree. It can also be trained as an espalier or shaped into
a hedge.
Prune as needed to
maintain the shape desired. In winter or early spring, last season's growth
should be pruned away, which will help produce bigger blooms.
Pests & Diseases of
Rose of Sharon:
Unfortunately, Japanese Beetles love the Rose of Sharon shrub.
Other pests include aphids and spider
mites.
Diseases include leaf
spot, blight, and cankers.
The buds may drop if the
plant is watered too much or too little, or if too much fertilizer is applied.
Pink Tropical Hibiscus (close relative) is pictured above left.
