Boerhavia coccinea

scarlet spiderling


Boerhavia coccinea

Mill. 1768

pronounced: boar-HAH-vee-uh kok-KIN-ee-uh

(Nyctaginaceae — the bougainvillea family)


common name: scarlet spidering

Boerhavia is named for Hermann Boerhaave (1668–1738), Dutch botanist; coccinea is from the Greek κοκκος (kokkos), the berry of the scarlet oak. The common name spiderling for the genus comes from the supposed resemblance of the numerous long, slender and interlocking stems of the inflorescences to a little spider.

The Boerhavia genus (often mis-spelt Boerhaavia) is variously described as containing between 17 and 40 species. There is quite a large variation within each species, and this has led to a great deal of taxonomic confusion, with several names having been given to the same species. This is not unique to this genus! A review currently being undertaken at Kew Gardens in London of the world’s million or so named plants has been able to confirm only a third of them as unique. A good example is a subspecies of the English Oak which has been ‘discovered’ 168 times. The Plant List recently published by Kew weeds out 51 synonyms for the common beech, 29 for the common daisy, 26 for the bluebell; the Giant Sequoia, native of Sierra Nevada in California, and now found in botanic gardens all over the world, has been named 18 times by different botanists. So far, Kew has found about 300,000 unique species, and 480,000 synonyms of those species. Another 260,000 names are described as ‘unresolved’, the Kew botanists so far unable to decide whether they are separate species or duplications. It’s no wonder that we are sometimes confused when trying to nail down a Magnetic Island plant!

Boerhavia coccineais a widespread plant whose native range is not certain, but probably includes the south-western United States and parts of Mexico. It is also now found, naturalized, in south-eastern USA, South America, Africa, Asia, Australia and on many Pacific Islands, including the Hawaiian Islands, where it is an invasive species and a noxious weed. It grows in a wide variety of habitats, including disturbed areas, and as a common roadside weed.

The scarlet spiderling is a low-lying, sprawling perennial herb producing reaching stems that can exceed a metre in length. These stems are often a reddish colour. The plants form large spreading mats on the ground. The generally oval-shaped leaves are held on short petioles. They are wavy along the edges, and may have reddish margins. They are opposite, with leaf pairs of unequal sizes. The foliage is sticky. The inflorescence is a small head of tiny frilly flowers, each just a few millimetres long. The flowers are magenta to dark wine-red in colour; they are 5-lobed, and are in clusters up to 13 mm wide. Magnified, they turn out to be very pretty.

This is quite a serious agricultural weed in some places. It is also a pest in lawns, particularly around the edges.

The plant is a food souce for the moths Megalorhipida leucodactylus and Cruria donovani.

Photographs taken in Picnic Bay 2010, 2011
Page last updated 20th October 2018