Drosera modesta — Vorstman's Guide to the Carnivorous Plants

Identification

A perennial that each year produces from an underground tuber a scrambling stem 30 to 80 cm long, which works its way up through the surrounding vegetation. Along the stem sit shield-shaped trapping leaves with conspicuously long tentacles that give the leaves a somewhat hairy, bristly look. The flowers are white and appear late in the season, in October and November. We did not find precise leaf and flower measurements in any source consulted.

Similar species

Other climbing tuberous sundews with white flowers, such as Drosera macrantha and D. pallida, look similar from a distance. D. macrantha has larger flowers and cup-shaped leaves with shorter tentacles. The long tentacles and late flowering are the best characters of D. modesta; in addition the species more often grows in the shelter of granite outcrops and stream banks.

The trap and how it works

An active flypaper trap. The shield-shaped leaf blades carry long tentacles with a sticky droplet at the tip. Because of their length these tentacles form a wider net than in most relatives, increasing the chance of catching flying insects among the shrubs. After a catch the tentacles bend to the centre of the leaf and digestive enzymes are secreted.

Habitat and ecology

Granite outcrops and stream banks, on laterite or sandy clay (R3, D3), often among shrubs and low vegetation (B5) where the stem finds support. Like all tuberous sundews the plant grows in the wet winter and survives the summer as a tuber; the late flowering in October and November suits places that stay moist longer.

Distribution and elevation

Endemic to south-west Australia. We could not obtain a precise distribution from FloraBase.

Recorded (quarter-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 31 quarter-degree squares in which the species has actually been recorded, from GBIF and only from records accurate to within five kilometres. They show where it has been seen, not where it occurs: an empty square means nothing. For threatened species this layer never goes finer than a whole degree, deliberately.

Forms and variation

No subspecies or varieties have been described. The species belongs to section Ergaleium, the erect and climbing tuberous sundews.

Where and when to see it

Go in October, when most other tuberous sundews have finished flowering; the white flowers of D. modesta then stand out more. Search the shady side of granite outcrops and along creeks, and look closely at the leaves: the long tentacles are visible to the naked eye.

Conservation status

On the global IUCN Red List the species is listed as Least Concern (LC). It is not listed in CITES. Granite outcrops and stream banks in the south-west are threatened by trampling, weeds and changes in hydrology. Uncertainty: we could not check the distribution within south-west Australia in detail.

Scientific name

Drosera modesta | Diels, 1904

Drosera modesta was described in 1904 by Ludwig Diels, in Botanische Jahrbücher für Systematik, volume 35, p. 209. No reliable type-specimen record with collection details could be found. The species is endemic to Western Australia and grows on granite outcrops and stream banks, but a precise type locality, collector or date could not be established with certainty. The name derives from Latin modestus/modesta, "modest, unassuming" — likely a descriptive name referring to the plant's inconspicuous, modest appearance (hence also the common name "modest rainbow"), though Diels's own original rationale could not be traced.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.