Drosera pycnoblasta — Vorstman's Guide to the Carnivorous Plants

Drosera pycnoblasta — the trap in close-up — **The trap in close-up** · Photo: Michal Klajban in cultivation — CC BY-SA 3.0 · Wikimedia Commons

Identification

A small rosette with stalked glandular blades; with the inflorescence the plant reaches 9 cm. The best character is the stipule bud at the centre: simple, broad stipules packed so densely that together they form a round ball. The name derives directly from this: pycnos is 'densely packed', blastos 'bud'. The flowers are white to pink and appear from September to November. Exact leaf and flower measurements are not published in the sources consulted.

Similar species

Many pygmy sundews have a stipule bud, but rarely one so compact and globular. Drosera leucoblasta has a white, looser bud and orange flowers; D. parvula and D. pedicellaris flower white but grow in the west and north-west. When in doubt a lens is needed to examine the shape and arrangement of the stipules.

The trap and how it works

An active flypaper trap in miniature. Each leaf blade, often no larger than a pinhead to a few millimetres, carries stalked glands on its margin and upper surface, each holding a glistening sticky droplet; the marginal tentacles are usually the longest. A small animal that touches the droplets sticks fast, after which the tentacles bend towards the centre of the blade and press the prey against the digestive glands. The glands secrete enzymes and absorb nitrogen, phosphorus and minerals from whatever dissolves. Given the scale, the catch consists of the very smallest: springtails, mites, aphids, thrips and minute midges moving over or just above the sandy ground.

Habitat and ecology

White or yellow sand (D1), in heath and scrub (B5) and in open mallee — the low, multi-stemmed eucalypt woodland of the dry interior (B6). One observer describes the plant in deep white sand in mallee north of Ravensthorpe, together with Drosera zonaria. The compact stipule bud suits this drier setting.

Distribution and elevation

Endemic to southern Western Australia, from around Brookton and Bruce Rock to Ravensthorpe. FloraBase lists the Avon Wheatbelt, Coolgardie, Esperance Plains, Jarrah Forest and Mallee bioregions and records the species from 23 local government areas. Altitudinal limits are not published.

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 39 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

Ludwig Diels described the species in 1904. No subspecies or varieties are recognised. Like all pygmy sundews it forms gemmae in the centre of the rosette in winter; the globular stipule bud is the most conspicuous part of that overwintering apparatus in this species.

Where and when to see it

Search in September and October in open sandy patches in mallee and heath on the sandplains; the white-pink flowers give the plant away fastest. Outside flowering, the round silvery bud at the heart of the rosette is the character to look for. In summer the plant has withdrawn into that bud and is almost impossible to find in the sand.

Conservation status

Assessed as Least Concern (LC) on the IUCN Red List; not listed in CITES, and rated not threatened in FloraBase. The species occurs over a large area. In the wheatbelt much of its habitat has been cleared; there it survives mainly on road verges and in reserves, and further east in the mallee in more extensive natural country.

Scientific name

Drosera pycnoblasta | Diels, 1904

Drosera pycnoblasta was described by the German botanist Ludwig Diels, in Botanische Jahrbücher für Systematik, volume 35, page 207, in 1904. The species is endemic to Western Australia. Diels described many new Western Australian species based on material he and Ernst Pritzel collected during their 1900–1902 expedition; it is plausible that the type specimen of this species comes from those collections, but the exact collection site, collector and date could not be confirmed with certainty. The epithet pycnoblasta is composed of the Greek pyknos ("dense") and blastos ("shoot, bud"), and thus likely means "with densely packed shoots/buds". This reading follows from the Greek construction but could not be confirmed in a dedicated etymological source.

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