Favourite Nectaring Plants

Butterflies' Favourite Nectaring Plants 
The Snakeweed (Stachytarpheta indica)

Butterflies need nutrients and sugars, besides other minerals, to survive and go about their daily business.  Very often, I have been asked what types of flowers are attractive to butterflies.  Over years of observations of our winged jewels, there are favourite species of flowering plants that attract butterflies more than others.  For example, if you want to attract butterflies to your garden, roses and orchids are flowering plants that you should not be cultivating!  

This series of blog articles will introduce our readers to the various types of all-time favourite nectaring plants that butterflies prefer.  Hence if you are cultivating a butterfly garden, these are the plants to look out for and include in your horticultural pallete.  

The first plant that will be featured is the common Snakeweed (Stachytarpheta indica).  

Plant Biodata :

Family : Verbenaceae

Genus : Stachytarpheta

Species : indica (syn. jamaicaensis, villosa) and mutabilis

Country of Origin : South America

English Common Name : Snakeweed, Purple Snakeweed, Blue Porter Weed, Pink Snakeweed

The Snakeweed has been described as an erect herb often growing up to 1m tall.  The leaves are opposite and usually bright green.  Each leaf is elliptic oblong and range from 4-11 cm long.  The margins of the leaves are toothed where the teeth are of varying sizes.  The secondary veins on the leaf are inconspicuous beneath.  Leaves can also be variegated on the same plant, but turning all green as they mature. 

Variegated leaf of the Snakeweed

The flowers are found on long, narrow spikes which can range from 15-40 cm long.  The corolla of the flower is bright violet, but there are white and red varieties as well.  The species mutabilis has larger flowers and are usually orange-red.  The corolla tube of the typical indica is pale bluish-violet with 5 short deep purple-blue lobes.  There are two stamens in the corolla tube. Fruits are small, dry and hard. 

Different colours of the Snakeweed flowers

The Snakeweed is typically found in wastegrounds as a weed.  It occurs in the nature reserves of Singapore along cleared paths.  This "weed" is now being cultivated in urban gardens and parks as a butterfly-attracting plant.  

Close up of the most common variety of the Purple Snakeweed flowers

The plant requires moderate watering, and is able to grow in poor soil.  It does well in both full sun and semi-shade. It grows as shrubs and older plants have woody stems.  It has a habit of growing tall and gangly as it matures, and rather sparse.  Leaves are sometimes attacked by insects and mould.  

Many species of butterflies are attracted to the flowers of the Snakeweed.  In particular, the purple variety, which is more common, are visited by almost all the families of butterflies, with the exception of species from the Lycaenidae and Riodinidae families which rarely visit the flowers. 

The common urban Papilionidae like the Common Mormon and Lime Butterfly find the Snakeweed very attractive, and we have observed the butterflies feeding on T. indica as well as the larger but rarer T. mutabilis. 





Of the Pieridae, the Grass Yellows (Eurema spp) are often attracted to the purple flowers of T. indica even in the nature areas, whilst the urban butterflies like the Catopsilia spp. (Emigrants), Psyche (Leptosia nina) and Painted Jezebel (Delias hyparete) often stop to feed at the Snakeweed flowers.  

The Danainae also love the Snakeweed, and we have seen the various Tigers and Crows feeding greedily on the flowers.  Over at Pulau Ubin Butterfly Hill, where the Snakeweed grows in abundance, the Common Tiger, Plain Tiger and the Black Vein Tiger are regular visitors to its flowers.  Members of the Crow (Euploea) family also visit the flowers, often giving a photographer a better chance at taking a good shot of the butterflies when they stop to feed at the Snakeweed.

The larger species of the Nymphalinae, like the Lacewings (Cethosia) - Malay and Leopard, are frequent visitors to the flowers of the Snakeweed.  The Great Eggfly (Hypolimnas bolina) has also been seen to feed on the Snakeweed flowers. The medium-sized species like the Junonia, Phalantha and Doleschallia also visit the Snakeweed flowers from time to time. 

There could also be a correlation between the weight of the butterfly species and the frequency with which these species visit the flowers of this plant.  "Heavier" and large butterflies like the Polyura, Lexias and so on have not been seen feeding on this plant before.  Interestingly, the Satyrinae also avoid the flowers of this plant.  Although, for example, where the Common Palmfly (Elymnias hypermnestra) and the Bush Browns (Mycalesis spp) are found flying in the vicinity of the Snakeweeds, I have only seen on one rare occasion where one of these species fed on the Snakeweed flowers.

Of the Hesperiidae, many of the smaller species love the Snakeweed, often seen zipping from flower to flower to feed.  Even the rarer "flats" (subfamily Pyrginae) visit the flowers. 

It will be interesting to keep a log and checklist of all the species of butterflies found feeding on the Snakeweed.  Obviously, the correlation between physiological attributes of the pollinating requirements of the plant and the types of butterflies and other insects (bees have also been seen at the flowers of the Snakeweed) would be important.  Attributes like size and weight of the butterfly, length and diameter of proboscis, the amount of nectar each flower produces to satisfy the needs of the butterfly and a myriad other considerations would determine why one species of butterfly visits the Snakeweed, and why another does not.  

Future articles in the series will feature other flowering plants that are favourites amongst the feeding butterflies as well as information about the plants themselves.  

Text by Khew SK  : Photos by Chng CK, Khew SK, Koh CH, Loke PF, Tan BJ & Anthony Wong

References :

• Keng, Hsuan : The Concise Flora of Singapore, 1990 ; Singapore University Press
• Foo, Tok Shiew : A Guide to the Wildflowers of Singapore, 1985 ; Singapore Science Centre
• Boo, CM; Omar-Hor, K & Ou-Yang CL : 1001 Garden Plants in Singapore, 2nd Edition, 2006 ; National Parks Board