Download Hardy Hibiscus - Cold Tolerant, Long

Cold Tolerant, Long-lasting, Beautiful Flowers
By Joe Wolf
Polk County Master Gardener
Some close relatives of the Chinese or Tropical hibiscus are
the hardy hibiscus which are also magnificent and deserve to
be better known. Many of the hardy hibiscus are native to
Florida and best of all are able to withstand freezing weather.
Most are native to swampy areas but some can also grow in
drier areas.
Hibiscus mutabalis Rubra
Confederate Rose
The Chinese hibiscus (Hibiscus rosa-sensensis) is one of the
most beautiful shrubs in Polk County. There are thousands of
varieties each more beautiful than the last. Each flower lasts
only one day, but if the bush is well taken care of, new
blooms will replace the old every day. The bush itself can
bloom most of the year. The Achilles’ heel of the Chinese
hibiscus is cold weather. Unless it is well protected, it can
freeze to the ground or freeze dead.
The hardy hibiscus can replace the Chinese hibiscus in areas
where freezes occur. Most will lose their leaves in the winter; in a very cold period they can
freeze to the ground, but will re-grow from the roots in the spring. Their flowers are even
bigger and brighter that the flowers of the Chinese
hibiscus.
There are 10 species of hardy hibiscus we can use
here in Polk County, plus there are several hybrids
that can be grown. The most common species are:
Rose-of-Sharon, Confederate Rose, Scarlet Rose
Mallow or Swamp Mallow, and Giant Rose Mallow.
These may be difficult to find at our local stores, but
seeds and plants are available on the internet.
Sometimes nurseries will order a plant for you, if
you ask them. All of them grow best in full sun and
in a wet area such as a bog garden. When not in wet
soil they will need watering during dry periods.
Hibiscus coccineus - Scarlet Rose Mallow
The hardy hibiscus most northern gardeners are familiar with is Rose-of-Sharon (Hibiscus
syriacus): it grows well over most of the United States except the coldest and warmest areas.
Here in Polk County it will grow best in some of the colder regions of the County. It is a multitrunk shrub that can grow from 8’ to 12’ tall and 4’ to 10’ in diameter. Generally it grows very
upright but it can get a little sparse. There are lots of cultivars of this species so you can get
flowers in red, pink, white, cream, gray, purple, blue,
and lavender. Blooms are about 3” in diameter. It is
fairly insect and disease resistant except for some
aphids, which are not really hard to eliminate.
Southern gardeners are more familiar with the hibiscus
Confederate Rose (Hibiscus mutabilis). It can freeze to
the ground during the winter but it will come back
Hibiscus aculeatus - Comfortroot
from the roots and still bloom. If it does not freeze it can grow to 15’ high and 10’ wide.
Generally it blooms in the late summer. Each flower can be 6” to 8” in diameter in a white that
turns to pink. Varieties have been developed that have double flowers ‘Floral Plena’ and
another, ‘Rubra’ with a deep carmine flower. This shrub will only grow to about 6’ tall.
Scarlet Rose Mallow or Swamp Mallow (Hibiscus coccineus) has brilliant red scarlet flowers that
can be 6” to 7” in diameter. It can die back to the roots in the winter but will re-grow in the
spring producing flowers all summer long. It is native to swamps in central Florida so it is best
planted near water or in a bog garden but can grow in drier soils with a little extra water in dry
periods to keep it flowering. It is a tall narrow sparse plant growing up to 7’ high.
Giant Rose Mallow is also sometimes called Swamp Mallow (Hibiscus grandiflorus). It has large
pink flowers (5” to 6” in diameter). It grows 10’ or more in height but only 2’ to 3’ in diameter
at the base. The leaves are grayish green and fuzzy on both the top
and bottom. This is another plant native to the swamps of Florida.
It needs to be planted in a wet area.
Other hardy hibiscus require special places to grow that many of
us do not have, but if you have a swampy area with full sun on
your property these other hibiscus could be wonderful for you.
Examples of these hibiscus are: Comfortroot (Hibiscus aculeatus),
Halberdleaf rosemallow (Hibiscus laevis) and Crimsoneyed
rosemallow (Hibiscus moscheutos). All of these are tall thin plants
with large colorful flowers.
Some of the hybrids even have larger flowers up to 1’ in diameter
Hibiscus Disco Blue hybrid
with colors from white, pink and into dark reds. Most grow upright but a few are smaller and
mounding or compact. All like full sun. Some examples include Blue River II (white), Disco Bell
(white and pink), Fantasia (pink), Fireball (red), Lady Baltimore (pink with red center),Lord
Baltimore (red), Rubra (red) Kopper King (pink with red center and burgundy leaves), and Super
rose (rose pink). These are just a few that are available; a much longer list can be found in the
IFAS article given below.
Hibiscus need watching; a number of bugs and fungi attack them. The worst of these are the larvae of
the hibiscus sawfly and other caterpillars. They also get whiteflies, grasshoppers, and spider mites but
these are easier to control.
For further information see:
http://edis.ifas.ufl.edu/pdffiles/EP/EP2
4500.pdf and
http://edis.ifas.ufl.edu/pdffiles/ST/ST2
9500.pdf
Hibiscus hybrids
Top left – Lady Baltimore
Top right – Fireball
Middle left – Double
Middle right – Yellow
Bottom – Turn of the Century