Mirabilis jalapa – 4 O’click flower.
Family Nyctaginaceae.
The Four o’clock flower opens from late afternoon and lasts until the next morning.
It is a naturalised garden plant that has escaped and become a weed in Queensland.
A bushy shrub-like perennial usually up to about 1 m high.
It forms large tubers – swollen areas on the roots that store food.
The branching stems are swollen at the nodes.
Leaves are opposite and decussate (alternate pairs at right angles).
The simple leaves are about 15 cm long and they have petioles.
The blade, with fine hairs, is lanceolate (widest below the middle).
The tip is pointed and the base is heart-shaped and sometimes unequal.
The flowers are deceptive as what looks like the petals is actually the coloured sepals and
what looks like the calyx are bracts (involucre – bracts subtending a flower).
Flowers, up to 6 cm long, are in clusters of up to 7 and have minimal or no stalks.
The funnel-shaped or salverform perianth consists of 5 sepals that are joined for over half
their length with the ends flaring into 5 rounded lobes.
The sepals can be a uniform pink, red, yellow, white or magenta.
Different coloured flowers may appear on a plant at the same time.
Sepals may be bi-coloured with sectors, spots or stripes in a second colour.
The colour combinations and the patterns also differ on the same plant.
As the plant ages the basic colour of the flowers can change e.g. magenta then yellow.
Flowers are bisexual.
There are usually 5 or 6 stamens with basally fixed anthers that open via longitudinal slits.
The ovary is superior and has 1 carpel, style and stigma.
The mature, spherical fruit are black and up to 10 mm long with 1 seed.
Fruits are dry and indehiscent.
J.F.
