Cardiospermum grandiflorum

Cardiospermum grandiflorum.

The Balloon vine is naturalised in S.E. Queensland where it is an environmental weed.
It is a fast-growing evergreen perennial vine that may become woody with age.
It climbs by tendrils and can smother other vegetation.

The much-branched stems can be up to 10 m long.
The circular stems are ribbed and densely hairy especially when young.
There are short white curled hairs and longer straight brown ones around 4 mm long.

The compound leaves, up to 18 cm long are alternately arranged.
They have a grooved petiole up to 10 cm long that is usually hairy.
The small stipules falls off early.

The blade is ternate with the leaflets in 3 groups of 3 with the terminal one usually being longer.
They are around 7 to 8 cm long on petiolules from 1 mm to 3 cm long.
Leaflets have a pointed tip and toothed edges.
The upper surface many have a few hairs and the lower has a few to dense ones.

A single hairy tendril arises from the axils and there are 2 near the end of the peduncle.

Axillary inflorescences are branched clusters on a peduncle 10 to 15 cm long.
The peduncles are hairy as are the pedicels which are up to 5 mm long.
There are small bracts and bracteoles.

Flowers are around 10 mm long and 5 mm wide.

There are 4 pale green sepals in 2 unequal pairs.
The ovate outer pair is 2 to 3 mm long while the inner pair, with concave tips is up to 8 mm.

They have 4 white, cream to pale yellow obovate petals up to 9 mm long.
The 7 mm long white petal-like appendages on each petal have a bright yellow upper edge.
Their sides are joined forming a corona.
Those on 2 of the petals form a hood over the stamens, glands and ovary.

The flowers are functionally unisexual.
There are 8 stamens of slightly different lengths.
They are on a short androgynophore which is on one side of the flower.
The bases of the white filaments often have white hairs on them.

The disc is in 2 parts – a short androgynophore on one side of the flower and 2 finger-like glands on the other side.
The 1 to 2 mm long glands are white and have long white hairs.
The hairy superior ovary, on the 1 mm long androgynophore has a single style with 3 stigmas.

The fruit are inflated, ovoid, angular, 3-chambered capsules 5 to 8 cm long.
They mature from green to pale brown and become papery.
The sepals remain attached at the base and the style forms a beak at the tip.
Each chamber has 1 smooth round green then black seed.
Capsules are covered in curled hairs.

The round, 5 mm long seeds are attached to a wing formed from the capsule septae.
The hilum where the seed is attached is variously described as oblong, round, ovate, heart-shaped or triangular.