RHS Journals

The Garden
May 2002

Yes, we have more bananas

The world's largest herbaceous plants, combining a small tree's stature with enormous yet graceful leaves, bananas provide an unmistakably tropical look. Several are proving surprisingly hardy in the UK, and Tim Miles believes there could be more on the way

Not since the reign of Queen Victoria have British gardeners had such an interest in growing bananas, and, unlike the late 19th century, we have a wide and increasing range of species and cultivars from which to choose. This is largely due to the increased interest in tropical and subtropical gardening within the UK, and bananas, with their giant leaves, have become one of the most exciting plants that can be grown outdoors here.
Un-named bananas offered for sale in garden centres are usually Musa acuminata 'Dwarf Cavendish', a traditional cultivar capable of producing delicious fruit - when grown in a heated glasshouse. Musa basjoo, commonly known as the Japanese banana (although, according to David Constantine of specialist banana nursery KobaKoba, it was originally from China), has been grown in Cornish gardens for more than a century. The banana relative Ensete ventricosum has long been used in subtropical bedding schemes throughout the country.
Some newly introduced bananas, as well as promising much for outdoor cultivation in the UK, may even be able to produce edible fruit (see growing bananas in the UK).

Basic characteristics

Bananas, the genus Musa, are the world's largest herbaceous plants, and around 50 species can be found from tropical Africa, India and southeast Asia to northern Australia. The family Musaceae also includes Ensete with six species. Species and cultivars from higher altitudes or latitudes tend to be the best for growing outdoors in the UK.
Musa have huge, paddle-shaped leaves that are prone to shredding by the wind, a natural damage-limitation device to prevent the whole leaf being broken off in tropical storms. The leaves split into parallel strips at right angles to their stout central midrib, which can look untidy but they still function effectively. Wind resistance varies considerably between species and cultivars.
The stout central 'trunk' that leads to bananas being regarded as trees is not woody, but made up of tightly wrapped leaf bases, so botanically is classed as a pseudostem. The growing point, at the tip of the true stem, remains deep inside the pseudostem at the base of the leaves, and in this respect bananas are broadly analogous to bearded iris and canna. Each shoot is monocarpic, dying after flowering, but basal suckers take its place.
Bananas have long been cultivated for their fruit, and over the centuries hybrids have been selected that form seedless fruit without pollination and fertilisation (parthenocarpy), as seed-containing fruit are generally regarded as inedible.

Garden use

All bananas make striking, large specimen plants and are usually deployed as such in permanent landscapes or seasonal displays, where their presence effortlessly evokes the ambience of exotic climes. They can look magnificent planted en masse, unfortunately seldom seen in Britain.
Even in Cornwall, Fox Rosehill Gardens and Heligan are the only places I know that grow them in this way. At the Cotswold Wildlife Park, Burford, Oxfordshire, we endeavour to immerse our visitors in the planting as they explore our Walled Garden. Musa basjoo is a vital element for this as its trunk is tall enough to allow the leaves to arch over the paths.
Ideal as the backbone or centrepiece of subtropical plantings, bananas combine well with other flamboyant tender species, providing a foil for the flowers of Canna (particularly cultivars with coloured leaves such as C. 'Striata'), dahlias and Eucomis, and contrasting with the foliage of bamboos, palms and Ricinus communis (castor oil plant).

Bananas to try in the UK

Musa basjoo
The 'Japanese' banana, introduced in 1881, soon became a feature of the great Cornish estate gardens and is now enjoying a revival of fortune. It has a slender trunk, 2-3m (61/2-10ft) high, with huge leaves, bending gracefully towards their tips, creating a dramatic effect. The plant is best grown in sunny, sheltered positions to prevent the wind from shredding its fragile foliage. In favourable seasons, an established, well-fed and watered plant may achieve combined trunk and leaf growth of up to 2m (61/2ft).
The plant usually produces its pendulous inflorescence during its fifth year. Female M. basjoo flowers are produced first, but they are no longer receptive when the later male flowers are producing pollen, so it is not self-fertile. Two separate plants would need to be flowered 'out of synch' for cross pollination, and it appears summers and autumns in the UK are neither reliable or warm enough to allow the development of fruit.
As with most banana plants, the leaves of M. basjoo are soon blackened by the first hard frost, although its rootstock seems hardy in much of the UK even without protection.
A thick mulch of straw or a similar organic material spread over the soil surface above the crown is recommended in colder areas.

Musa basjoo 'Sakhalin'
This selection is reputedly from the Russian island of that name, to the north of Japan on the same latitude as the Cornish 'Banana Belt' around Falmouth. Unlike Cornwall, Sakhalin Island is not subject to the warming effects of the Gulf Stream, so is likely to be colder in winter, lending credence to the claim that the form from this island is perhaps the hardiest selection of M. basjoo.
Andy Bateman of Mulu Nurseries has known this cultivar to survive -7°C (19°F) virtually unharmed, although he believes that in the trade this selection may have become confused with the type species, which looks almost identical.

Musa sikkimensis (syn. M. hookeri)

Introduced by seedsman Toby Spanner in 1998, following an expedition to northeast India, this species is easily raised from seed, attaining more than 2m (61/2ft) in its third year at the Cotswold Wildlife Park. Hardiness in the UK is, as yet, uncertain, although there is optimism it could be on a par with M. basjoo. Seed-raised plants are variable, but in general the more upright leaves have an attractive maroon midrib with some plants having prominent markings on the upper surface of the younger foliage. However, they are less graceful than the leaves of M. basjoo and appear to be more prone to shredding in the wind.

Musa lasiocarpa (syn. Musella lasiocarpa)

Resembling a shuttlecock in form, Musa lasiocarpa, with its conical red and green pseudostem, can reach 1.5m (5ft) in height outdoors in the UK	Due to its yellow inflorescence Musa lasiocarpa, first found in Yunnan, is known to the local population as 'yellow lotus of the earth mother'

A dwarf Chinese banana recently reclassified as Musa from its own monotypic genus, M. lasiocarpa reaches only 1.5m (5ft). Its conical trunk and grey-green leaves give it a 'shuttlecock' outline and the yellow, waxy, globe-artichoke-like inflorescence can last for several months. It is wind resistant and the rootstock is hardy with winter protection. Arguably the ideal potted banana for patios or small gardens, it suckers freely and is more readily available thanks to micropropagation.

Musa 'Dhussray'

Grown in the foothills of the Himalayas in North East India, fruits of this banana are sold in the markets of Sikkim and Darjeeling. These particular areas are marginal for banana production due to the cold nights with occasional frosts in winter but the fact that these plants survive there makes them an exciting prospect for year-round planting, and possible flowering, in the UK. Too large to fruit in most domestic glasshouses in the UK, young Musa 'Dhussray' can still make attractive , slightly glaucous, foliage plants.

Musa species from Yunnan
This is an undetermined species collected at high altitude in Yunnan. It is a graceful plant having slender pseudostems and arching blue-green leaves. It is showing promising cold tolerance, overwintering successfully outdoors in the UK with protection.

Other Musa cultivars
A number of cultivars of Musa are currently being evaluated for their fruiting potential in the UK.

Ensete
Species of Ensete are closely related to Musa, botanically separated by the fact that Ensete species do not normally produce suckers.

Ensete ventricosum

So-called Abyssinian or Ethiopian bananas were a great favourite for Victorian bedding, and have again become popular in exotic schemes. One of the most tropical-looking foliage plants for growing outdoors in the UK, in summer it often produces a new leaf each week. These can reach more than 3m (10ft), their undersides usually displaying a striking red midrib. The plant can attain 12m (39ft) in the wild, and the leaves seem more resistant to shredding than many bananas. A naturally variable plant, seedlings of Ensete ventricosum may vary greatly in colour, particularly in the intensity of the red midrib

Ensete ventricosum 'Maurelii'

Sometimes sold as E. ventricosum 'Rubrum', this cultivar has rich reddish-maroon young leaves, fading to a colourful orange-red edge when older. A gorgeous-looking plant, it is slightly less hardy and vigorous than the type species and does better in containers during summer, as it dislikes being transplanted. One of the most richly coloured plants of the banana family, and coming from Ethiopia, it is best displayed outdoors in large containers and overwintered under glass.

Ensete glaucum

A little less vigorous than E. ventricosum, its outstanding glaucous 'trunk' may prove taller. Its hardiness in the UK is uncertain .

Ensete superbum

Said to have the appearance of a huge bird's nest fern, this Indian species can grow to 4m (13ft). Treat as for E. ventricosum 'Maurelii'.

The growing interest in bananas seems set to continue particularly given the increased range now available. Try exploiting their translucent qualities by positioning them to be backlit by the low evening sun of late summer and autumn. By this time the leaves are at their largest, with animated shadows of nearby plants cast upon them, shifting in the slightest of breezes and bringing a real flavour of the tropics to any garden.

Compact Musa laterita is a small, easily flowered species producing striking red bracts, given winter protection under glass in Britain	Sadly, Musa 'Tapo' from Papua New Guinea, with its unusual red-and-green marbled leaves, is only suited to cultivation under glass in the UK

Propagation
Suckers of Musa basjoo may be removed at any size in spring or summer providing they have some independent root. Sever the sucker from the main shoot with a spade or bread knife and ease the roots out with a garden fork, taking care not to damage the trunk underground. Remove some older, lower leaves from the sucker to reduce transpiration, pot up (avoid overpotting) or replant and keep compost moist but not wet.
Ensete species are best raised from seed as they do not naturally produce suckers. Soak seed in tepid water for 24 hours prior to sowing. At the Cotswold Wildlife Park, we sow in a 1-litre pot placed inside a 3-litre container, the cavity filled with perlite to insulate the pot and maintain soil temperature. Add an insulated lid then place in a polythene bag and provide bottom heat. Germination occurs in two to three weeks but is often sporadic; pot up emerging seedlings and return other seeds to heat. Expect around 50 percent germination.

Pests and diseases
Bananas out of doors in the UK are virtually trouble free. Under glass, red spider mite can take a grip. Regular misting with water of the undersides of the leaves is a good preventative measure. If infestations of mealybug occur in the roots, wash all the compost from the root system with a water jet, and repot the plant having reduced the plant's leaf area.

Overwintering
The largest garden plants of Musa basjoo are individuals that have their trunks protected from temperatures below -4°C (25°F). In late autumn, remove the leaves with one horizontal cut towards the top of the trunk.
A straw coat, supported with chicken wire, posts and canes, is cheap and rustic, if a little untidy. This can be covered with horticultural fleece for added protection and to keep the straw in place.
Glazed chimney-flue liners are available in short sections that can be added to each year as the trunk gains height. Plastic drainage pipe, 60cm (2ft) in diameter, is also suitable. This is available double-skinned and can be filled with straw to provide additional insulation.
Most species and cultivars grow more vigorously if planted out for summer, although success can be had with plants grown in large containers. We usually lift ensetes in late October or the beginning of November, but fleece is on standby should an early hard frost threaten.
Lift with a fork, taking care not to pierce the stems. The extensive root system has to be reduced drastically to within 5-10cm (2-4in) of the trunk in order to containerise these giants (even then a well-grown, three-year-old Ensete may require a 70-litre pot). Remove some of the older leaves to compensate for the root downsizing, water the compost and then allow to gradually become dryer.
To overwinter Ensete, our glasshouse is kept at 16°C (61°F) by day and 12°C (53°F) at night - at lower temperatures, lifted plants are prone to rotting. The lower the overwintering temperature, the earlier Ensete should be lifted and established in their winter containers, and the drier they should be kept subsequently. If only frost-free winter quarters are available, permanent container culture may be wiser. Musa species and cultivars are more forgiving of this operation, and can even be stored in a shed or garage.

Fruiting cultivars for cool conditions
There are more than 300 fruiting cultivars of Musa, a number of which are now available in the UK. In the most sheltered spots these could be planted permanently in the garden and given winter protection. Alternatively, keep them containerised and move them indoors during winter. Given the extended growing season possible under cover,
this may make fruiting more likely.
KobaKoba's David Constantine suggests that Musa cultivars such as 'Rajapuri', 'Orinoco' and 'Dwarf Orinoco' are most suitable for this purpose, and can be overwintered in just frost- free conditions. Andy Bateman of Mulu Nurseries adds 'Brazilian' to this list.
Musa 'Malbhog', 'Haharé', 'Chini Champa' and 'Dhussray' are all cultivars from northeast India where they are subject to cold nights and some frost. These have been introduced to the UK by David Constantine.
In favoured locations such as Cornwall, the race is now on to produce edible bananas outdoors in the UK.

Tim Miles has been growing bananas for 20 years and is a writer, broadcaster and member of RHS Floral 'C' Committee

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