Native plant notes: What is diallagy?

Most people have seen deciduous trees change colour before dropping their crisp, drying leaves in response to seasonal drought (in our region) or low temperatures (in cold climates) and then grow fresh new leaves when conditions improve.

However, only a few of our group had observed diallagy – or even heard about it – until we went out to White Mountains National Park in noticeably drier conditions than our previous trips.

Photo: John Elliott

‘Diallagy’ describes a remarkable adaptation to survive drought, seen in diverse native plants in Western Australia and a few native species in Queensland. Unlike deciduous leaves, diallagous leaves remain on the plant, retain their normal texture, and revert back to their usual green colour after sufficient rain has fallen.

Near our lunch spot we found Thryptomene parviflora (photo above) had changed its normally green foliage to a glowing reddish-brown. The leaves were lustrous and alive, not dying as we tend to assume for brown leaves. Even more surprising, this plant was bearing a few fresh flowers (photo below).

Photo: John Elliott

We also saw the transition to diallagy in Hibbertia ferox (aka ‘Betsy’s fierce Hibbertia’) with some of its leaves still green while most of its foliage had changed to brown (photo below).

Photo: Julia Hazel

Pete sent in a very interesting article about diallagy in WA by Alex George, who coined the term in 2001. For copyright reasons, we can’t publish that article, but if you’d like to request a copy for personal use, you can Contact Us.

Plant of the month 06/2023: Pittosporum tinifolium

Photo: Malcolm Tattersall

On our June outing at Cleveland Creek, we noticed clusters of tiny creamy-white flowers (photo above) on a small tree that presented an ID challenge for most of us. Thanks to John for providing the answer: Pittosporum tinifolium.

Photo: Russell Cumming

Pittosporum tinifolium (Pittosporaceae) is one of several trees commonly called Rusty Pittosporum. This attractive species was previously considered a variety of the widespread rusty-leaved pittosporum complex and named P. ferrugineum subsp. linifolium. Its separation as a species and the correction of ‘linifolium‘ to ‘tinifolium‘ is explained here: https://www.qld.gov.au/__data/assets/pdf_file/0020/69041/cayzer-chandler-austrobaileya-v10s1-p205-206.pdf

Identifying features are described by Cayzer and Chandler (see PDF linked above) as follows:

Leaves elliptic to almost orbicular, thick-coriaceous, upturned, apices rounded or acute; inflorescences multi-flowered stalked umbels exserted well past surrounding foliage. Common and endemic
to coastal areas south of Cooktown, in Cook, North Kennedy and Port Curtis districts, Queensland.

Photo: Russell Cumming

Older leaves of Pittosporum tinifolium are almost hairless/smooth (‘glabrous’ is the proper term) and the ‘rusty’ common name refers to the new growth covered in fine rusty hairs (photo above).

Photo: Russell Cumming

The woody fruits of Pittosporum tinifolium are initially green, becoming yellow to orange (photo above) before splitting open at maturity (photo below).

Photo: Russell Cumming

The genus name Pittosporum is derived from two Greek words meaning pitch (sticky) and seed. Pittosporum tinifolium fits that idea nicely with its bright red, sticky seeds displayed after the orange-coloured seed capsules split open (photo above).

Plant of the month 05/2023: Corymbia serendipita

Photo: Peter Horsfall

Corymbia serendipita, common name Newcastle Range Bloodwood, is a new record for the Burra section (eastern side) of White Mountains National Park, discovered by Peter Horsfall during our NPQ May outing.

Pete’s sharp eyes picked out these trees as something different among many diverse eucalypts in the Burra area, and he took on the challenge of identifying them correctly.

Notably, the trunk of Corymbia serendipita (Myrtaceae) has rough, flaky and scaly orange-yellow bark (first photo below), shedding higher up to leave the upper branches smooth, pale grey to white (second photo below).

Photo: Peter Horsfall
Photo: Peter Horsfall

The leaves are narrow and lance-shaped, slightly darker green on one side than the other, and the tree holds its fruits/seed capsules erect above the foliage (photo below). There were no flowers visible on it in May.

Photo: Peter Horsfall

Seed capsules that Pete measured were 8 mm long x 5 mm wide, urn-shaped and covered with small pustules (photo below).

Photo: Peter Horsfall

Corymbia serendipita is an uncommon tree, endemic to northern Queensland. Typically it grows on higher, drier sandstone and ironstone plateaus, mainly in the Newcastle Range (hence its common name) between Einasleigh and Forsayth, south to Oakleigh Station, and at Cobbold Gorge.

You can find more information about this species (and other eucalypts) in two excellent resources that are freely available online:

Plant of the month 04/2023: Hibbertia advena

Guest post by Dr Betsy Jackes with photos courtesy of Rigel Jensen/Australian Wildlife Conservancy

Photo: Rigel Jensen/AWC

This rare Hibbertia from Taravale has just been named Hibbertia advena by Tim Hammer, Helmut Toelken and Kevin Thiele. The Latin ‘advena’ means outside, foreigner or stranger. This is a reference to the fact this Hibbertia is clearly related to species in southwest Western Australia and not closely related to other pungent-leafed Hibbertia species in Queensland.

Photo: Rigel Jensen/AWC

Where has Hibbertia advena been found?
At the western edge of the Australian Wildlife Conservancy (AWC) Mt Zero-Taravale Wildlife Sanctuary, and at one location near the top of the Ben Lomond Mining Lease. Since this area has not been well explored, there are probably isolated populations still to be found.

Photo: Rigel Jensen/AWC

How do you recognize Hibbertia advena?
It is a much-branched prickly shrub with scattered, linear, pungent leaves and strongly rolled margins so that the midrib on the lower surface is obscure. The flowers are borne on small pedicels (stalks). The 15 stamens are divided into 5 distinct groups of 3 and these groups are inserted between the 5 carpels.

Photo: Rigel Jensen/AWC

How does it differ from the ferocious Burra Range species, Hibbertia ferox?
Hibbertia ferox has only 2 carpels that are surrounded by 9-10 stamens and the flowers are sessile i.e. without a pedicel. The leaves are similar but tend to be crowded rather than scattered.

Reference: Hammer, T.A., Toelken, H.R. & Thiele, K.R. (2022). Hibbertia advena (Dilleniaceae), a new and rare species from Queensland with transcontinental affinities. Australian Journal of Taxonomy 9: 1–5. doi.org/10.54102/ajt. Illustrations p 4.

Plant of the month 03/2023: Heliodendron basalticum

Photo: Julia Hazel

Thanks to John for pointing out this Heliodendron basalticum (photo above) on our recent outing beyond Hervey Range. It was another “new” species for many of us!

Heliodendron basalticum (Fabaceae) synonym Archidendropsis basaltica is an endemic Queensland species with leathery bi-pinnate leaves, sometimes deciduous in dry seasons.

This small tree grows naturally across a wide range in central Queensland. It is known by two common names, Red Lancewood and Dead Finish. The first refers to its dense, straight-grained wood with red tones. The second supposedly came from Indigenous people, who knew the drought-hardiness of this tree, saying “if dis tree die, dis country dead-finish”. Confusingly, the name Dead Finish is also used for other quite different species e.g. Acacia tetragonophylla.

Photo: John Elliott

Heliodendron basalticum has globular yellow flowers (photo above) and large seedpods (photo below).

Photo: Russell Cumming

Heliodendron basalticum is not commonly cultivated but a specimen has grown well in a Townsville garden, photographed as a small seedling in 2010 (first photo below) and flowering in 2018 (second and third photos below).

Photo: Russell Cumming
Photo: Russell Cumming
Photo: Russell Cumming

Plant of the month 02/2023: Sannantha papillosa

Photo: Russell Cumming

Sannantha papillosa (previously called Babingtonia papillosa) was a Show and Tell item at our February meeting – thanks to Charles! We didn’t have time to discuss this interesting species then, so we’ll give it Plant of the Month attention instead.

Sannantha papillosa (Myrtaceae) is listed as Vulnerable under the Queensland Nature Conservation Act because the species occurs naturally in only a few isolated places. One of its locations is revealed by its common name “Mt Elliot Myrtle” but only hardy bushwalkers get to see it thriving on the mountain’s exposed rocky outcrops (photo below).

Photo: Russell Cumming

On the surface of its branchlets (photo below) Sannantha papillosa has ‘papillose’ oil glands (small raised pimples) that distinguish it from other similar species.

Photo: Russell Cumming

Sannantha papillosa was enthusiastically propagated in the early 1990s from Mt Elliot seed by members of Townsville SGAP, now NPQ. The first cultivated plants have provided seed for many subsequent generations grown by our members and by the Landcare nursery.

The species has proved adaptable to local garden conditions, preferring sunny areas with good drainage, and from an early age it puts on a fine show of abundant small white flowers.

Photo: Russell Cumming