If you like gaudy, showy,
outrageously flashy flowers then hardy hibiscus is the plant you want to grow. Rose
Mallow, as it is often called, is native to the wetlands of the American
southeast, which gives the plant another common name, Swamp Mallow.
The huge, saucer shaped
blooms have a tropical flare, but don’t confuse them with the tropical
hibiscus; these are hardy to at least zone 5. Most gardeners will find hardy
hibiscus easy to grow and a glorious finale of late summer color in the
garden.
Hardy Hibiscus plants are
superb for marshy, wet areas, poolside and rain garden plantings. Smaller
varieties make impressive container plants.
The flowers are attractive to bees, butterflies and hummingbirds also.
Hibiscus moscheutos, the hardy hibiscus, is often confused with Rose
of Sharon, or with tropical hibiscus. They are often all mixed together in
garden shops. Rose of Sharon is also hardy, but the plants have woody stems,
which survive the winter, and the blooms are smaller. Tropical hibiscus has
large flowers but the leaves are different, smaller and lobed, and the flowers
are often shades of yellow, and orange or doubled. The leaves of hardy hibiscus
are broadly triangular in most varieties, and the flowers of hardy hibiscus do
not come in true yellow and orange and are generally single.
There is an Asian species of
hibiscus, Hibiscus mutabilis, hardy to about zone 7, that does have
double flowers and leaves shaped like maple leaves. It is sometimes called
Confederate Rose Mallow. The Confederate Rose Mallow has broad, lobed leaves
somewhat like a maple. To add to the confusion this species has been crossbred
with H. moscheutos, producing interesting varieties for gardeners, but
still more confusion in the garden shop. Hybrids may have purple leaves that
are 3 lobed, somewhat like a Japanese maple leaf. If you are looking for true
hardy hibiscus, check the plant label for zone hardiness and a Latin name.
The flowers of hardy hibiscus
are round and flat, ranging from 6 inches to more than a foot across. They are
shiny, with prominent veins radiating out from the center and a sort of crepe
paper look. Hardy hibiscus has enlarged stamens and pistils in the center of
the flower, often in a ring of contrasting color. Colors of hardy hibiscus range from white
through shades of pink and red, including a plum red that is almost purple. While
there is one variety that claims to be yellow, it is a very pale cream color at
best. Many flowers have a ring of darker
color in the center. Each flower is open only a day, but mature plants with
plenty of moisture produce enough flowers to make a long show, usually blooming
from late summer to frost.
Growing Hardy Hibiscus
Hardy hibiscus or Rose Mallow
can be started from seeds and if started early indoors, may bloom the first
year. The seeds are slow to germinate and need to be kept constantly warm and
moist. Start them at least 2 months before your last frost and transplant
outside after all danger of frost has passed.
Hardy hibiscus is also sold as a potted plant, or as dormant root
pieces. Potted hibiscus should be planted in the ground soon after you buy
them, at least six weeks before your first fall frost, for best survival of the
first winter.
Hibiscus prefers full sun and
moist soil. They will grow and even bloom in part shade, although the plants
won’t be as full and flowering stems may need staking. Some varieties will
require staking even in full sun, especially in windy areas. Hardy hibiscus
plants produce several stems from the ground that may reach 5 foot tall or
greater in moist, sunny areas.
Rose Mallow isn’t fussy about
soil, but that soil should be kept well watered; the plants will thrive in rain
gardens or marshy areas. A slow release fertilizer can be used in the spring as
shoots emerge.
Hardy hibiscus dies to the
ground in the winter. The location of the plants should be well marked as they
are very slow to start growth again in the spring, waiting until the soil
reaches about 70 degrees before sprouting new growth. This late start is why zone 5 is about the
limit for growing hardy hibiscus, they may survive zone 4 winters but not have
time to bloom before frost.
Some named varieties
Disco Belle comes in white,
pink and red flowers. The plants are compact at 2-3 foot with 9 inch flowers. Southern Belle is larger, at 4-5 foot high,
and has flowers 10-11 inches wide in a range of pink, red and white. ‘Kopper King’ is one of the hybrids, it has
purple foliage and huge, light pink flowers with a red eye and red veining. ‘
Crown Jewels’ also has the purple foliage but on a more compact 3-4 foot high
plant, and white flowers with a red eye that are about 6 inches across. ‘Moy
Grande’ is a huge hibiscus, plants may reach more than 5 foot tall and the rosy
red flowers are over 12 inches across. ‘Old
Yella’ is the closet to yellow hibiscus, actually a creamy white, 10 inch
flower on a 4 foot plant. ‘Plum Crazy’ has deep, plum-red, 10 inch flowers on a
compact 3-4 foot plant with purple foliage.
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