The genus Hibiscus includes many shrubs, some herbs, and trees. Leaves are lobed (palmately) or entire.
The common name is Mallow or Mallow Rose; and the genus comes from the family Malvaceae
Flowers: Mainly solitary, usually bell shaped, 5 petals, distinctive style with anthers attached.
Flowers vary in colour, shape and habit. main flowering period in throughout warmer months however spot flowers at other times do occur.
Features: Hedging plant, flowering specimen, standards, espalier,may be bird attracting.
A good plant to use to give the 'Hawaiian' affect.
Requirements: Fertile and moist, but well drained soil required that is slightly acid to neutral.
Heavy clays subject to water logging are particularly bad for these plants.
Sandy soil is preferred. When preparing the soil for planting, ensure plenty of organic matter is added. If soil is clayey, make raised garden beds, plus use gypsum on the natural soil.
Tropical to subtropical. Does not like frosts or severe wind.
Culture: Gross feeders - fertilise every two months for maximum flowering.
Mulch well and prune to shape. Pruning is usually carried out in early spring as new growth commences; this encourages multiple branching and increases the number of potential flowers. Propagate annuals or species treated as annuals by seed, herbaceous perennial types by seed or division, shrub cultivars (e.g. H. Rosa-sinensis & H. syriacus) by cuttings, grafting or layering.
Hibiscus grow best when not in competition with other plants for water, fertiliser and sunlight. Set aside a garden bed just for them.
Severe salt spray damage may occur if planted along the coastal beaches. Hose the plants down will reduce some of the salt burn damage.
Pest & Disease: The range of pests include: Hibiscus beetle, mites, scale, mealy bugs, aphids, whitefly, thrips, grasshoppers, caterpillars, slugs, leafminers, cutworms. Disease include: Leaf,spots, mildew, sooty mould root rots and collar rots. Viral disease do occur in hibiscus.
A range of chemicals are available to the gardener. Most reliable products are Carbaryl, Diazinon, Endosulfan. For disease use Mancozeb or Fongarid. Always read the label to ensure it is register for use with hibiscus. There is no control measure for viral infections.
Species & Varieties:
There are approximately 250 species, including:
H. calophyllus -A perennial herb or shrub to 3m tall, broad leaves to 15cm long, and about 15cm wide, with solitary yellow flowers with a reddish or brownish base to 10cm across.
H. cameronii -Medium shrub to 2m with palmate leaves and pink petals flushed to red at base.
H. heterophyllus -An erect, evergreen shrub or small tree to 5m, from Australia, with often spiny branches, leaves to 20cm long, sometimes lobed, solitary flowers in the upper leaf axils, white petals to about 8cm long with a crimson base.
H. Rosa-sinensis -Variable in colour, these plants tend to grow to 3m with upward or weeping foliage.
Some varieties of H. rosa-sinensis:
Red: Big Tango, Catavki, Mollie Cummings, Mrs. Heywood, Nagao 20
Gold: Bruceii, Crimson Ray, Firefly, Golden Belle, Happiness, Meteor
Lemon: Delight, Full Moon, Kwai Matsai, Miss Kitty, Vasco
Orange: Fiesta, Flame, Frank Green, Miss Hawaiian, Surfrider, Tangerine
Apricot: Celia, Cyclops, El Capitolio Sport, Gold Dust, Honey Do
Cream/White: Bride, Dainty Lady, Erma K., Madonna, Snowflake, White Picardy
Pink: Boondah, Charles September, Flower Girl, Hawaiian Sunset, Katy D
Lavender/Mauve: Dusky Beau, Isobel Beard, Lady Adele, Lavender Lady
Browns: Devil's Gold, Eclipse, Dr. Gillette, John F. Kennedy
Multicolours: Aloha, Cinderella, Halea Kala, Midnight Frolic, Norman Lee
Miniatures: Ali Uli, Fiji Island, Psyche, Sylvia Goodman
Doubles: Crown of Bohemia, Flamingo Star, Happy New Year, Jerry Smith
H. Moscheutos (Wild Cotton, Mallow Rose) -To 3m tall deciduous perennial with red, pink of white flowers.
H. mutabilis (Cotton Rose, Confederate Rose) -A shrub or small tree to 5m, broad leaves to 15cm long, and about 15cm wide. Flowers about 8cm long, petals pink to reddish with a darker base.
H. syriacus (Rose of Sharon, Althaea) -An erect shrub or small tree to about 4m, triangular to rhombic-ovate leaves mostly less than 8cm long. Flowers on short pedicels in the upper leaf axils. Flowers can be single or double, with petals up to 8cm long, mainly whites, reds, purplish or bluish lavender. Has been proved to grow well in drier districts.
A few cultivars have been produced including: 'Alba Plena', 'Hinomaru', 'Sokobeni Yae' and 'Woodbridge'.
H. schizopetalus (Japanese hibiscus) -A semi-weeping plant to 3m with fringed red flowers. Other colour forms are now available.
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In Australia: www.acs.edu.au/Courses/horti.aspx
In the UK: www.acsedu.co.uk/Courses/horti.aspx
Tropical Plants Course:http://www.hortcourses.com/courses/tropical-plants-bht234-404.aspx