Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Sapindales
Family: Sapindaceae
Subfamily: Sapindoideae
Genus: Cardiospermum
Species: C. grandiflorum
Binomial name: Cardiospermum grandiflorum
Common names: Balloon vine, Heart pea, Heart seed

Cardiospermum grandiflorum is a species of long-lived, perennial, climber-vine native to eastern Argentina and Brazil. It is an invasive climber growing in damp situations. It forms dense but localised infestations and can grow to enormous lengths and is capable of smothering a tree 10m tall. It competes with and smothers indigenous plant species by preventing their ability to effectively undergo photosynthesis. It invades forest margins, watercourses and urban open spaces. Cardiospermum grandiflorum ability to spread rapidly & tolerate a wide range of habitats makes this vine a serious potential threat to NZ.

Cardiospermum grandiflorum stems are ribbed. The stems, flower stalks and fruits are all covered in short, stiff, bristly hairs.
Leaves are (compound) made up of 3 lots of 3 leaflets. Leaflets are toothed or lobed. Leaves may be up to about 16cm long.
Cardiospermum grandiflorum’s small white flowers have four petals; they are fragrant and occur in clusters. The stalk of the flowerhead ends in a pair of tendrils.
The fruit is a membranous, 3-sided papery, balloon-like seed capsule which is initially green but dries to a brown colour.
The black seeds are round and have a heart-shaped hilum. This is the seeds point of attachment to its seed capsule. The seeds are transported by wind and water, mostly while attached to membranous inner walls of the fruit.

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The hairy leaves and stems.
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An unripe seed capsule
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A ripe seed capsule
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Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/