Drosera adelae

Lance-shaped leaves for a shady stream bank

Most sundews have small leaves and grow in open, well-lit places ^[3]. Drosera adelae has long, narrow, lance-shaped leaves, 10 to 25 cm long on short stalks, sticky on the upper surface and margins and smooth underneath ^[4]. P. S. Lavarack of the National Parks and Wildlife Service saw these large, broad leaves in the three Queensland rainforest sundews as an adaptation to low light ^[3].

The flowers come in winter and spring, 10 to 20 on a one-sided spike 20 to 35 cm long, with small petals 2 to 3 mm long ^[4]. The Flora of Australia notes that the species is related to D. indica and separates it by its lance-shaped leaves with stipules, a notched anther connective and two-parted styles ^[4].

Young plants look different from adults. Juveniles of D. adelae and its relative D. schizandra have rounder leaves on clear stalks, and very small plants of all three rainforest species cannot be told apart ^[3]. ICPS makes the same point: the mature leaves of the “three sisters” (D. adelae, D. prolifera and D. schizandra) look very different, yet the juvenile leaves and the flowers are similar, and the three are more closely related to each other than to any other sundew ^[2].

Three sisters, three small ranges

All three species grow along streams in a small area of coastal mountain rainforest in northeast Queensland. D. adelae occupies about 70 km around Rockingham Bay and Hinchinbrook Island, from sea level to at least 450 m. D. schizandra grows about 100 km to the north on Mount Bartle Frere, and D. prolifera another 140 km beyond that, around Thornton’s Peak near Cape Tribulation ^[2].

In the wild D. adelae grows in beds of moss on creek banks, usually in shade ^[3], and among rocks and sedges beside rainforest creeks ^[4]. Lavarack described the habitat of all three as warm and humid, with little change in temperature or moisture, low light and a well-drained substrate. Their streamside colonies are flooded by fast-flowing water for up to a day or two several times a year ^[3].

Rainforest is a hard place for a flypaper trap. ICPS points out that rain washes prey off the leaves, that carnivorous plants in very rainy places tend to have pitchers instead, and that ants take prey from D. schizandra and, to a lesser extent, from its sisters ^[2]. These sundews seem to specialize in small insects that can be held and digested quickly ^[2].

Lavarack called D. adelae a rare plant in 1979, because its range is so small ^[3]. IUCN has since assessed it for the Red List; see the assessment for its current category ^[5]. Like every native Queensland plant it is protected under the Nature Conservation Act 1992 ^[6], and it is not listed under CITES ^[7].

Growing it: humidity before light

ICPS ranks D. adelae among the easiest sundews to grow. It grows as well in pure water as in any of its neighbors’ soil mixes, and it can become a weed, sending out long roots that sprout new plants in nearby pots ^[2]. Its one firm demand is humidity. It does best in very humid air and is a poor house plant unless your home is very humid, though it does not need the very warm temperatures of its native forest ^[2]. That points to a terrarium or a humid greenhouse; see terrariums and humidity and growing carnivorous plants indoors.

Light needs are lower than for most sundews. The ICPS lighting table puts it at moderate light, about 8,000 to 15,000 lux of white light, compared with 15,000 to 25,000 lux for most Drosera, and warns that strong blue/red lamps can be too much ^[8]. Grower Roger Hoelter, writing in Carnivorous Plant Newsletter in 1988, kept all three sisters under fluorescent tubes for 16 hours a day. D. adelae went in the brightest spot in the center, D. prolifera toward the edges, and D. schizandra at the edges and shaded by other plants. He found that D. adelae kept growing and multiplying in fairly dry air, but its tentacles dried up so it no longer looked like a sundew ^[9]. See light for carnivorous plants.

Hoelter grew his plants in a 50:50 mix of milled sphagnum peat and vermiculite in pots about 8 to 10 cm (3 to 4 in) deep, standing continuously in reverse-osmosis water ^[9].

Feeding: the sources disagree

ICPS says the plant declines if not fed well and does best on live small flies such as fruit flies. It adds that D. adelae is less sensitive to foliar fertilizer and dried bloodworms than its sisters ^[2]. Hoelter’s experience was harsher: he wrote that fertilizer was lethal to all three species, after healthy plants he had fertilized disintegrated in less than a week ^[9]. Given that disagreement, small live insects, which ICPS recommends, are the cautious choice; the feeding guide explains the options.

Propagation from roots, leaves and flower stalks

ICPS calls D. adelae very easy to propagate from leaf cuttings, root cuttings and flower stalks ^[2]. Hoelter’s original plant died weeks after he bought it, but half a dozen new plants came up from roots he had laid horizontally just under the surface of the mix. Most of his later plants arose the same way, and occasionally from lower leaves lying on the soil ^[9]. For leaf cuttings, ICPS floats leaves tentacle side up in pure water in a closed jar or tube and expects little to happen in the first month ^[10]; see sundew leaf cuttings.

Seed is rare. The plant flowers only occasionally, the flowers do not self-pollinate, and hand pollination may give a seed or two ^[2]. For other sundews by growing group, see the genus overview.