Whenever your arboretum curator is on a nature walk, she is always on the lookout for uncommon native species and unknown plants. Recently such a case occurred when we spotted a cluster of small, brown papery husks in some damp undergrowth. Upon inspection these were the fruit of a ground-trailing vine with parsley-like leaves.
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| These seed pods draw the eye, as they look quite strange and unnatural. |
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| The leaves are distinctly parsley-like or cilantro-like. |
Each fruit was a capsule made up of three separately inflated lobes, each of which contained a single seed. The seeds are spherical and mostly black with a single a round, cordate, or fabiform white marking. Immature fruit were papery but green instead of brown, with green seeds instead of black & white. Upon consultation of the literature, we first believed this to be Cardiospermum halicacabum, the Balloonvine or Heart-seed. The first name explains itself, while the second refers to how the white spot can resemble a heart. This curious plant is a member of the Soapberry family (Sapindaceae). It likes wet areas and is able to colonize disturbed and marginal environments.
The proper domain of this species is a bit confused. Found across the subtropical and tropical regions of the globe, this plant is native to Mexico, the Caribbean, northern South America, sub-Saharan Africa, and subtropical Asia from India to Melanesia.
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| Current distribution of Balloonvine in the Southeast, according to the USDA-NRCS |
Guy L. Nesom, in his 2009 article Assessment of invasiveness and ecological impact in non-native plants of Texas categorized this species as "F2:Abundant in number and widespread, commonly invasive in disturbed habitats, much less commonly in natural habitats; subdivided into woody, herbaceous, and aquatic species."
Nor is it much appreciated where it appears. Consider the US state of Georgia, in which "It is unlawful to sell, offer for sale, or expose for sale any agricultural or vegetable seed" contaminated with forty named species. Thirty are restricted, allowing only a certain number of those species seeds per pound of agricultural seed. The same is true in the state of Louisiana: Balloonvine is entirely prohibited. Even a single seed cannot be mixed in with agricultural seed without incurring a violation. This is particularly a problem with soybeans because the seeds of Balloonvine can closely resemble a soybean, although the average Cardiospermum halicacabum seed is only as large as the smallest soybean.
Is it all bad? No. The European Agency for the Evaluation of Medicinal Products has written that extracts of Cardiospermum halicacabum
have legitimate veterinary and hygienic uses, given that it contains
anti-inflammatory properties and is insecticidal and anti-bacterial.
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| Cardiospermum is taxonomic Latin for "heart-seed," but something is funny here. I'm not seeing any hearts. These are Lunaspermum or Demispermum at best. Is there some significance to the lack of hearts? Is this normal variation within the species or should we be uncertain about the identification? |
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| Compare with this image, courtesy of fairdinkumseeds.com. There's quite a difference; these seeds have a distinctive heart-shaped white spot. |
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| Back to ours. The left-most seed has been sliced in half, revealing that an opaque milky-white endosperm layer rests within the black-and-white seed coat. |
Upon further reflection, we are not sure what we've got on our hands. These seeds lack the distinctive heart-shaped white marking. It very well could be another member of the genus Cardiospermum, and even be a species native to the Southern US, if not our local area. But how can we tell? Consider this opinion from the North American Butterfly Association's page on Cardiospermum corindum: "Confusingly, all five of the vines are often referred to as ‘balloon
vine’ or ‘heartseed’. Frustratingly, there seems to be mixed opinions as
to the native status of the various balloon vines." You can say that again.
Twice above we've mentioned that this plant has parsley-like leaves. Cardiospermum corindum, the likliest candidate for this specimen after Cardiospermum halicacabum, has the common name of Faux persil. Persil is the French name for the culinary herb parsley, which ultimately derives from the ancient Greek "petros" meaning stone and "selinon" meaning celery.
Unfortunately photos of this genus online are in a very disordered state. It's just not possible to decide on what we're looking at. Due to the ambiguous nature of this plant, we won't transfer it to the arboretum. But if we find some growing there, we won't pull it up, either. It's not much of a leap from Mexico or the Caribbean to Caddo parish, and if this species finds a home here, that's fine with us.
