Hibiscus is a varied genus, ranging from tender types that need to be kept in pots inside, to shrubs that can be grown in the garden. Their main attraction is the beautiful trumpet-shaped blooms with long stamens. They are long-flowering too - the indoor varieties can bloom from March to October, the hardy ones from late July until September.
Retailers can stock both types to attract different customers. The indoor plants are generally bred from Hibiscus rosa-sinensis, the Chinese hibiscus. It is a tender species, needing a minimum of around 7 degsC to 10 degsC, so best grown in a warm position in indirect sunlight. The species grows up to 2.5m tall in the wild, but its 120-plus cultivars are either compact, bushy plants or strong erect forms. The flowers are single or double and colours range from red, to pink, to orange, yellow and white, with many variations in between.
The most widely used hardy species are the broadly similar H. syriacus and H. sinosyriacus. The main differences between the two are that the former has more spreading growth and the latter is more upright, with fractionally broader leaves and slightly larger flowers. H. sinosyriacus is the more tender of the two, but will still tolerate down to -15 degsC. Customers may need to be warned that they do not leaf-up until at least June, so should not be declared dead too soon.
Among the species of Hibiscus sold as half-hardy annuals by seed companies are H. trionum and H. moscheutos, with its dinner-plate sized blooms. Among the less well-known tropical species available in the UK is the incredible H. schizopetalus, which has red flowers with dissected petals and long stamens, which hang down and resemble Japanese lanterns.
Indoor Hibiscus are best in large pots in a fertile, loam-based mix. They need plenty of water when in growth but in the winter should be kept much drier. H. rosa-sinesis, H. mutabilis and H. coccineus need minimum temperatures of 7 degsC to 10 degsC. The tropical species, such as H. schizopetalus, require 10 degsC to 16 degsC. Young plants should be tip-pruned so they bush out, and plants can be cut back hard in the spring.
The hardy species likes a well-drained, fertile soil in full sun and appreciates being mulched before winter. Long shoots may be tipped back immediately after flowering. Overgrown specimens may be cut back hard and thinned out in spring.
A problem to watch out for with Hibiscus is bud drop, caused by dry conditions or low temperatures. Pests that affect the genus are mealy bugs, greenhouse whitefly, soft scales and peach potato aphid.
Note that the word "hibiscus" is also used informally to refer to plants of the genus Alyogyne, a fellow member of the mallow family endemic to Australia.
Matthew Tanton-Brown, plant centre manager, The Place for Plants, Suffolk "Hibiscus are showy plants, which can be seen from quite a distance. They make a good focal point.
"We grow the hardy types H. syriacus and H. sinosyriacus and they can be a bit tricky to keep happy on the nursery because they run out of nutrients very quickly and don't like sitting in pots too long. But they are reasonably easy to grow once planted in a border. They like a hot and sunny position, being quite drought-tolerant.
"The best sellers are the blue-flowered varieties, like H. syriacus 'Oiseau Bleu' Award of Garden Merit (AGM). I like the Chiffon series too, which has elegant, semi-double flowers composed of two rows of tissue paper-like petals. There are lilac, white and blue forms, of which my favourite is 'White Chiffon' because it shows off other plants in the border. But you need to avoid putting it in too sunny a position because its flowers can get scorched."
Heather Godard-Key, owner, The Old Walled Garden Nursery, Warwickshire "We grow around 40 varieties of H. rosa-sinensis, which have flowers in many different shades, from apricot, to pale pink, to vivid velvety reds and blues. I find it hard to choose a favourite as I love them all. They are ridiculously flamboyant, long-flowering plants.
"H. 'Dorothy Brady' is a nice, easy variety that is a strong grower. It's big and blowsy, with semi-double pink flowers. Then there is 'June's Joy', which is fairly easy to grow. It has clear red flowers with apricot margins.
"From time to time we grow H. mutabilis, which has an incredible flower. It opens white then changes to pink over the course of the day, with its petals curling in on themselves. It can be used as a great talking point at a dinner party, because if cut, put into the fridge and then put out on the table your guests will see it mutate from a white dinner-plate-like flower into a pink pom-pom.
"The indoor varieties do well as long as in the winter they are given minimum warmth of 10 degsC and kept dry. In the house they are happy in a position with natural daylight but prefer not be in direct sunlight - the flowers will last longer. They can attract whitefly but they are not a beacon for anything else."
Nigel Eaton, head of the RHS Wisley Plant Centre, Surrey "We get the houseplant types in flower and they attract impulse buys from the customers. We used to call the outside varieties the 'nurseryman's nightmare' because they don't shoot until mid April. People used to buy them and then bring them back thinking that they weren't alive. Once they are in full flower in August, sales are fine.
"We usually display them with other plants - including Verbena bonariensis and V. rigida - which set them off nicely, especially the variety H. syriacus 'Oiseau Bleu'.
"In the retail environment they just need to be kept ticking over - they are not overly thirsty or hungry. The indoor varieties should be deadheaded regularly to encourage more flowers to come."
SPECIES AND CULTIVARS
- H. coccineus is a herbaceous species with cannabis-like leaves and large, red flowers, though these are not a certainty in the British climate. It is best overwintered inside and used as a tall bedding plant in a tropical scheme. Likes its feet in water. Height up to 2m.
- H. moscheutos is a perennial species sold as seed in the UK and treated as a half-hardy annual. It is useful for planting in the border, for large pots on the patio or in the conservatory, with impressive dinner plate-sized blooms. Height is 50-80cm.
- H. rosa-sinensis is the Chinese hibiscus, an evergreen flowering shrub. The species has a red flower but numerous cultivars have been bred and produce flowers of white, yellow, orange, scarlet and pink, with both single and double sets of petals. It is a tender variety.
- H. rosa-sinensis 'Apple Blossom' has single, pale pink flowers with a dark pink eye, and a vigorous and upright habit.
- H. rosa-sinensis 'Courier Mail' has large single flowers that have attractive mango-coloured petals with a peachy pink base. It has a tidy, upright habit.
- H. sinosyriacus is one of the species hardy in this country. It is similar to H. syriacus - a deciduous shrub or small tree growing up to 3m tall - but has larger leaves that are up to 10cm across.
- H. sinosyriacus 'Lilac Queen' is a form with white flowers, which are lightly tinted mauve and have a burgundy base.
- H. sinosyriacus 'Ruby Glow' has flowers with white petals and a red base.
- H. syriacus is a hardy deciduous shrub, with showy flowers in shades of white, pink, red or lavender. They may have dark-coloured centres and can be single or double. The leaves have serrated edges.
- H. syriacus Blue Chiffon = 'Notwood3' (PBR) is a member of the Chiffon series, bred by Dr Roderick Woods. The burgundy-centred blue flowers have a lacy centre of lighter lavender-blue petals that give it a semi-double appearance. Height is from 2m to 3m, spread 1m.
- H. syriacus 'Oiseau Bleu' Award of Garden Merit (AGM) (often named as H. 'Blue Bird') is considered by many to have the best single blue flowers. The base of the petals has striking reddish-purple markings that surround the white centre. It has a height 3m and spread of 2m.
- H. syriacus 'Purpureus Variegatus' is a deciduous shrub with pale-yellow and green variegated foliage. In summer and early autumn it bears large, single maroon flowers.
- H. syriacus White Chiffon = 'Notwoodtwo' (PBR) AGM has large, single, white flowers up to 12cm across with a lacy centre from August to October. The leaves are lobed and dark green. There is also a popular lavender form.
- H. syriacus 'Woodbridge' AGM is a late-flowering shrub that has large, trumpet-shaped, deep pink flowers with red centres from August to October. Height is 3m and spread 2m.
- H. schizopetalus is a shrubby species with arching branches from which hang fantastic flowers with frilly petals and long slender stamens. Several interesting common names have been coined including coral or skeleton hibiscus or Japanese lantern. Tender variety.