14 July 2009
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Hibiscus

The hardy hibiscus adds a dash of the tropics to any garden with its colourful trumpet-like flowers.

Recommended varieties

The choice of hibiscus is limited to two deciduous shrubs and their many cultivars.

The main differences between the deciduous H. syriacus (from eastern Asia) and H. sinosyriacus (from west China) is that the former has spreading growth and the latter is much more upright with slightly broader leaves and larger flowers, and is a bit more tender. Both flower from late summer to mid autumn.

H. sinosyriacus: branches form an open shrub with a good show of the characteristic, trumpet-like white flowers marked red in the centre.
H. sinosyriacus 'Lilac Queen': similar in all respects, except the flowers are lilac with a red centre.
H. syriacus: slightly taller and narrower at 3m (10ft) high and 2m (6ft) wide, with rich pink flowers, a dark red centre and yellow anthers.
H. syriacus 'Meehanii': grown for its attractive leaves with creamy white margins and small, pale purple flowers with darker centres. A weak grower that needs warm, sheltered-corner conditions. Has been given the Royal Horticultural Society (RHS) Award of Garden Merit (AGM).
H. syriacus 'Oiseau Bleu': exquisite, lavender-blue blooms, stained maroon at the base. Has been awarded the RHS's AGM.
H. syriacus 'Red Heart': stunning white flowers with a patch of dark red in the centre. Has been awarded the RHS's AGM.
H. syriacus 'William R Smith': highly rated pure white flower with tissue-like petals. Has been awarded the AGM.
H. syriacus 'Woodbridge': rich pink flowers. Has been awarded the AGM.

As well as the single-flowered hibiscus, some doubles are available:

H. syriacus 'Lady Stanley': has been grown for more than 100 years. The flowers form a mass of white petals, flushed deep maroon.
H. syriacus 'White Chiffon' and 'Lavender Chiffon': both bred recently by Dr Roderick Woods, an amateur hybridiser in Cambridge. Both have a neat twirl of smaller petals inside the outer ones. Doubles can be disappointing in a cool, wet autumn as the petals tend to hold the rain and get damaged. Stand up well to autumn weather.

Growing tips

Site and soil preferences

Hibiscuses like rich, moist, free-draining soil with all the sun they can get. They do particularly well in areas of low rainfall.

Planting

Although you can plant hibiscuses at any time if grown in a container, people tend to buy them when they're in flower.

If you buy one in summer, water it regularly until it's established.

Planting associations

As they have a long dormant period, hardy hibiscus plants should be positioned towards the back of the border with shorter plants, such as perennials and bulbs, diverting attention from their bare stems.

The lavender-blue H. syriacu 'Oiseau Bleu'makes a wonderful combination with silver-leaved plants, such as Elaeagnus 'Quicksilver' and Pyrus salicifolia 'Pendula'.

Aftercare

Once hardy hibiscuses get going, they need little care to keep them in tip-top condition. They're not hungry but appreciate a mulch of compost in spring.

In spring, they have the unnerving habit of playing dead, but don't be fooled. Hardy hibiscuses are late to come into leaf and their twiggy, grey stems often stay bare until June. When the leaves do emerge, they're usually pale yellow but soon darken.

Pruning and training

Hard spring pruning isn't difficult and promotes a mass of stunning, large flowers. You can also train hibiscus plants as standards, which make magnificent focal points in sheltered gardens.

In spring, be bold and reduce a plant to one stem and then train it up a stout cane. All subsequent side shoots should be removed until the plant reaches the desired height. Let the shoots develop at the top until there's a bushy head, and regularly prune each spring for shape and to promote plenty of large flowers.