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Boerhavia glabrata Blume 1826
pronounced: boer-HAH-vee-uh GLAB-rah-tuh
(Nyctaginaceae – the bougainvillea family)
synonym: Boerhavia dominii Meikle & Hewson 1984
pronounced: boer-HAH-vee-uh doh-MIN-ee-eye
common name: Tar Vine
Boerhavia is named for Hermann Boerhaave (1668–1738), Dutch botanist, professor of botany and medicine at Leiden University. He much improved the botanic garden there, and published numerous works describing new species of plants. Glabrata is from the Latin glaber, hairless, bald. In the synonym, dominii is from dominium, property, right of ownership, lordship, rule.
This is a fairly insignificant-looking weed that likes to cover bare ground; yet its tiny flowers are very pretty when looked at closely, as are also its fruit. There is a great deal of confusion about the identification of the members of this genus, and although I think I have got this one right, there must still be some doubt. It is also possible that there is more than one species here. There seems to be a great deal of intra-species variation, and although it is possible that the plants here are all within a single species, that might not be the fact. No two authorities seem to agree on the list of species within the genus, or on the names or synonyms of any particular species. I wonder whether the intra-species variation has caused some botanists to believe they have identified new species, when in fact they haven’t.
The flowers may be white, pink or mauve; the leaves may be narrow or wide, the leaf margins may be entire or sinuate, sometimes reddish in colour and sometimes not, and the growth habit may be prostrate or decumbent when the plant is growing on bare ground, or somewhat scrambling when it meets other ground cover.
The plant usually has a large, fairly thick taproot. The stems are glabrous, or with short glandular hairs; the leaf blade to about 4 cm long and 2 cm wide, lanceolate to ovate, the petiole 1–3 cm long. The flowers are in compound umbels, 2–10 flowered, and with 2–4 stamens, and the fusiform fruit is glandular-hairy with 5 longitudinal ribs.
Although we on Magnetic Island are not much bothered by feral camels, it may be of some comfort to any gardener trying to eradicate tar vine to know that camels love to graze on it. A 12 year period of observations on 5 cattle stations in central Australia rated all species of Boerhavia growing there as ‘highly preferred food plants’ for the million or so feral camels that roam the centre of the country: so, if you cannot eradicate the weed, perhaps a pet camel is the answer.
The plant is a food souce for the moth Cruria donovani.
There is a species of the genus, Boehavia erecta , originating in tropical America, that is a really serious invasive species. It is a spreading, herbaceous plant that grows to about a metre, and rapidly invades annual crops such as maize, sorghum, peanuts, beans and also young orchards and the understoreys of native woodlands, smothering vegetation and providing almost impenetrable refuges for feral animals. Although it is now widespread in Africa, India, Thailand, China, Indonesia, New Guinea and western Polynesia, it has not yet been recorded in Australia. Its sticky seeds spread long distances by attaching themselves to clothing, footwear, fur, feathers, farming implements and vehicles, which are all possible modes of entry into Australia. I fear that it is only a matter of time.
Photographs taken in Picnic Bay 2010
Page last updated 24th July 2018