Musaceae, the Banana Family, had 6 genera now reduced to 3 – Ensete, Musa and Musella.
Musa has around 40 species (30 – 50) from tropical Asia and Africa.
Banana plants, growing up to 12 m high, look like a tree but are a herb.
The ‘trunk’ is a non-woody pseudo stem made up of the tightly packed, overlapping leaf sheaths.
The actual stem is an underground rhizome with a number of growing points from which the
leaves and flowers grow.
Pseudo stems die after flowering and are replaced by new ones growing from the rhizome.
The spirally arranged leaves, up to 3.5 m long, form a crown at the top of the pseudo stem.
A tree has up to 12 or 15 oval, oblong or lanceolate leaves that are up to 60 cm wide.
They have a grooved petiole whose base expands into the sheath.
The edges of the sheaths are free.
The blades are penniveined and tear easily between the veins.
The terminal, erect or pendulous inflorescences do not grow from the pseudo stem.
A stalk or shaft grows from the rhizome up through the centre of the pseudo stem.
At the tip a large purple bract protects the terminal bud.
The inflorescence has a stalk or peduncle which continues as the flower bearing rachis.
The rachis has spirally arranged clusters of flowers, in double (single) rows, along it.
Each cluster or hand is protected by a thick bract or spathe that may fall off when the flowers open.
Bracts can be purple, green or brown and occasionally yellow.
Hands can have up to 20 bananas.
The flowers in the lower 5 to 15 rows are female with reduced stamens (or bisexual) and the
terminal ones are male with rudimentary ovaries.
There are some sterile bisexual flowers between the male and female flowers.
In many cultivated bananas all the flowers are sterile or neutral with new plants being
clones sprouting from the rhizome.
The perianth has 6 tepals with 5 united to form a tube and one free.
The slender tube, with 5 pointed lobes, splits down the inner side to the base.
The tepals are mainly white but can also be cream, purple, pale yellow and the tips may be a darker colour.
Male flowers have 6 stamens in two whorls but one stamen in the inner whorl is usually missing or is a staminode.
The anthers open inwards via longitudinal slits.
The male flowers and their bracts may fall off after about a day leaving a bare rachis.
There are septal nectaries, on top of a rudimentary ovary, that produce nectar.
The female flowers open before the males.
The inferior ovary of 3 fused carpels has 3 locules that can have hundreds of ovules.
Placentation is axile.
The terminal style holds the large, 3-lobed stigma.
The stamens are reduced to staminodes or are missing.
The fruit are berries.
Most are thin cylinders up to around 35 cm long that are straight or curved.
Others are short or nearly round and up to 8 cm across.
The thick or thin skin, initially green, ripens to white, yellow, red or orange.
Wild bananas have small seeds but commercial hybrids have only tiny dark undeveloped ovules.
Hybrids & cultivars.
There are hundreds and possibly up to a thousand varieties and cultivars.
The same common names are used for more than one cultivar.
Most cultivated bananas, often referred to as Musa x paradisiaca, are hybrids of M. acuminata and M. balbisiana.
In Australia the vast majority of bananas grown are Cavendish and its varieties.
Lady fingers would be the next most common and for home gardeners the ‘Dwarf Cavendish’ only grows
to 1 or 2 m with male flowers and bracts that do not fall off.
The large Cavendish plants are up to 5 m high with a green and brown pseudo stem and
long bunches of bananas. The male flowers and bracts fall off early.