Bloodthirsty plants of SA: Sundew, the sweetly-named plant with a sinister secret!

A fly­trap cousin of Venus

Drosera is tak­en from the Greek droseros, mean­ing dewy. It refers to glis­ten­ing droplets on the leaves of plants in the Dro­cer­acea fam­i­ly. This is the same fam­i­ly as the world’s best-known car­niv­o­rous plant, the Venus’ fly­trap (Dion­aea mus­cip­u­la, not a native of Australia).

Car­niv­o­rous plants tend to grow where soil nutri­ents are scarce, cap­tur­ing insects to use as a nutri­tion­al sup­ple­ment – nature’s mul­ti­vi­t­a­mins and minerals!

How does a sun­dew trap insects?

Sun­dews pro­duce sticky ​‘dew’ from glands at the tip of fine hairs. The nec­tar-like dew is attrac­tive to insects who seek a sweet meal, but they become trapped in the sticky goo. 

Some of our sun­dews have ​‘trig­ger’ hairs that flick the insect into the cen­tre of the leaf. More hairs move inwards to wrap around the insect, and in some cas­es the whole leaf curls over too. 

The dew con­tains enzymes which break down the insect so its nutri­ents can be absorbed by the leaf’s surface.

Four types of sun­dew to find in South Australia

Around 17 dif­fer­ent species of sun­dews are cur­rent­ly recog­nised in South Aus­tralia, with some unique to our state. They take four dif­fer­ent main forms:

• Low rosettes of round­ed leaves, which may be green or have a deep red­dish tint.
• Climb­ing sun­dews with small, cupped leaves dis­persed over del­i­cate, long branch­ing stems.
• Longer, thin­ner leaves with an upright growth habit.
• The forked sun­dew whose long, thin leaves fork into two or more parts, each cov­ered all around with fine, dew-tipped hairs.

Where and when can I find sundews?

Sun­dews are com­mon amongst native veg­e­ta­tion in the Mount Lofty Ranges, Fleurieu Penin­su­la, Kan­ga­roo Island and areas of South Australia’s south east.

Look for them from late autumn through to ear­ly spring. 

The small, tuber­ous rosette-shaped sun­dews are usu­al­ly the first to appear and flower, in the under­storey of wood­lands and around the edges of wet­ter areas. 

You might spot them on the edges of walk­ing paths, where they can form lit­tle dewy clusters.

In arid areas of South Aus­tralia, sun­dews can pop up at the edges of creeks, lakes and water­holes after sea­son­al rains and floodwaters.

Once you start notic­ing sun­dews, you’ll become famil­iar with the types of areas and con­di­tions they like. 

As with a lot of Australia’s fas­ci­nat­ing flo­ra, they’re small and sub­tle, but well worth seek­ing out.

How do sun­dews reproduce?

(If that’s not too per­son­al a ques­tion!) Many of our local sun­dews are tuber­ous peren­ni­als, mean­ing they regrow each year from an under­ground tuber; a kind of thick­ened stem that stores nutri­ents and ener­gy while the plant is dormant. 

After flow­er­ing and set­ting seed, the plant forms anoth­er tuber, so it can increase its fam­i­ly clus­ter as well as spread­ing its seed.

Oth­ers grow new plants just from seed. Sun­dews in more arid areas pre­fer this kind of repro­duc­tion, because seeds can sit dry and dor­mant for a few years before the con­di­tions are right to ger­mi­nate again.

Can I grow sun­dews at home?

First­ly – it may seem obvi­ous – but don’t take any sun­dews that you find grow­ing in the wild. For more about native plant laws and per­mits, have a look here: Depart­ment for Envi­ron­ment and Water — Col­lect native plant mate­r­i­al .

You may be able to find sun­dews or seeds sold by spe­cial­ist plant nurs­eries and collectors.

To mim­ic a sundew’s nat­ur­al envi­ron­ment you will need a low-nutri­ent grow­ing medi­um, and a con­stant sup­ply of rain­wa­ter or oth­er source of low-min­er­al water. 

Depend­ing on the vari­ety it will grow as an annu­al and die off com­plete­ly, or need a dor­mant sea­son each year. 

And of course, a sun­dew will want access to tiny liv­ing bugs as food.

Sound a bit fussy? In gen­er­al, unless you have a real­ly green thumb and lots of enthu­si­asm, it’s best to sim­ply enjoy sun­dews where you find them.

The sun­dew bug

South Australia’s own State Herbar­i­um has been involved in a num­ber of recent stud­ies involv­ing our fas­ci­nat­ing sundews. 

One has been a study of the sun­dew bug, in col­lab­o­ra­tion with ento­mol­o­gist Dr Ger­ry Cas­sis. 

The bug (Seto­coris) has the abil­i­ty to walk on sun­dew leaves with­out get­ting stuck, and helps itself to a meal of oth­er bugs that are trapped. 

Is it sim­ply steal­ing from sundews? 

In fact, it might be help­ing by pre-digest­ing and eav­ing its drop­pings as fer­tilis­er, and pro­tect­ing the plant from preda­tors. It seems to be a win-win partnership.

Ecosys­tem impor­tance of sundews

Sun­dews con­tribute to their ecosys­tems by nutri­ent cycling, as they cap­ture and digest insects and bring the good­ness down into the soil. They also help sta­bilise bog­gy and sed­i­men­ta­ry soils. Although sun­dew leaves seem unpalat­able to ani­mals, the tubers are some­times a food source for for­ag­ing mam­mals such as bettongs.

Sun­dews at risk

Sun­dews are vul­ner­a­ble to cli­mate change and habi­tat change, par­tic­u­lar­ly when there is extend­ed drought. If rain doesn’t occur until lat­er in the sea­son, the sundew’s grow­ing peri­od is cut short and it may not have the oppor­tu­ni­ty to ful­ly mature and opti­mal­ly reproduce.

Sus­tain­ing South Australia’s sun­dews involves the pro­tec­tion and restora­tion of habi­tats like wet­lands and wood­lands, and glob­al cli­mate action. As part of South Australia’s pre­cious bio­di­ver­si­ty, these sticky lit­tle won­ders are impor­tant to pre­serve for gen­er­a­tions to come.

With thanks to: 

State Herbar­i­um of South Aus­tralia — Prof. Michelle Way­cott, Chief Botanist

Nation­al Parks & Wildlife Ser­vice — Heiri Klein, Con­ser­va­tion Ecol­o­gist, Kan­ga­roo Island

- Antho­ny Abley, Con­ser­va­tion Ecol­o­gist, Ade­laide & Mount Lofty Ranges