Drosera broomensis — Vorstman's Guide to the Carnivorous Plants

Drosera broomensis — the flower — **The flower** · Photo: Denis Barthel — CC BY-SA 3.0 · Wikimedia Commons

Drosera broomensis — the trap in close-up — **The trap in close-up** · Photo: Topi Pigula — CC BY 4.0 · Wikimedia Commons

Drosera broomensis — the habitat — **The habitat** · Photo: Denis Barthel — CC BY-SA 3.0 · Wikimedia Commons

Identification

A small perennial sundew with a low, leafy rosette from which one to four flowering stems arise. The whole plant can reach 30 cm. The key feature is the completely glabrous inflorescence, scape included; in most relatives of the petiolaris group stem and calyx are hairy. The flowers are white and appear in February and March, late in the wet season. As throughout the group, the leaf consists of a narrow petiole ending in a small, round blade bearing tentacles.

Similar species

The closest relative is Drosera petiolaris, the most widespread species of the group, ranging from northern Australia to New Guinea. Other species of the same subgenus in the Kimberley include D. derbyensis, D. caduca and D. brevicornis, which Lowrie described in the same paper. The glabrous flowering stem is the most practical distinction; in the other species stem or sepals are covered in white hairs.

The trap and how it works

An active flypaper trap. The round blades at the ends of the petioles bear stalked glands with sticky droplets. An insect settling on one sticks, the tentacles bend towards the prey and the glands secrete digestive enzymes. In the petiolaris group the blades are small relative to the long petioles, so the traps project like little spoons around the heart of the rosette.

Habitat and ecology

Sandy soils (FloraBase), north and north-east of Broome, in the open savanna landscape of the Dampierland coast (D1, B6). The climate is monsoonal: a hot, very wet season from December to March and a long dry season. Species of this group usually survive the drought with thickened roots and a resting rosette, or protected by white hairs on the petioles that keep the plant cool and limit water loss.

Distribution and elevation

Endemic to the north of Western Australia. FloraBase lists the Dampierland and Great Sandy Desert bioregions; the species grows in the coastal area north and north-east of Broome.

Recorded (one-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 8 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No subspecies or varieties have been described. The species belongs to subgenus Lasiocephala, which numbers some fourteen species, mostly in northern Australia. Natural hybrids occur within the group, but none involving D. broomensis is mentioned in the sources consulted.

Where and when to see it

Flowering falls in February and March, in the middle of the rainy season, when roads around Broome are sometimes flooded. Afterwards, at the start of the dry season, the rosettes can still be found. Search open, sandy patches among the grass. The glabrous flowering stem is visible to the naked eye when compared with a hairy relative; bring a hand lens for the leaf hairs.

Conservation status

Assessed as Least Concern (LC) on the IUCN Red List and listed as not threatened in Western Australia. Not in CITES. The coastal zone around Broome is under pressure from urban expansion and infrastructure, but most of the habitat lies in little-developed country.

Scientific name

Drosera broomensis | Lowrie, 1996

Described by Allen Lowrie in 1996, in Nuytsia, volume 11, no. 1, p. 55-69 — the same publication as D. brevicornis. Earlier specimens had already been collected from 1891 onward, but the species was only formally described in 1996. Sandy soils north and north-east of Broome, Kimberley region, Western Australia. Named after the town of Broome, Western Australia, where the species grows.

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