Plant of the month 04/2024: Micromelum minutum

Photo: Julia Hazel

Micromelum minutum got our attention by putting on luxuriant clusters of fragrant flowers (photo above) during the first half of April. This attractive species, commonly called Lime Berry, will often flower and fruit several times a year under good conditions.

Photo: Russell Cumming

Micromelum minutum (Rutaceae) occurs naturally across much of northern Australia, growing as an understorey shrub or small tree (photo above) in drier rainforest, monsoon forest and coastal vine thickets.

Photo: Russell Cumming

After a particularly good Wet Season Micromelum minutum may bear flowers and fruits concurrently, making a stunning display (photo above). The flowers attract many bees and butterflies while the leaves host larvae of several butterfly species. The fruits, initially bright green, gradually turn orange and then deep red (photo below). When ripe, they are favoured by native fruit pigeons and other birds.

Photo: Russell Cumming

Plant of the month 03/2024: Bursaria incana

Photo: Julia Hazel

On our March outing we drove from Mingela to Fanning River, en route finding numerous Bursaria incana in full flower. Close up, their dense clusters of small flowers (photo above) are sweetly scented. In the middle and far distance their snowy canopies stand out while flowering (photo below) although at other times Bursaria incana is fairly inconspicious.

Photo: Julia Hazel

Bursaria incana (Pittosporaceae) is one of only 8 species in the genus Bursaria, all of them endemic to Australia. Bursaria incana grows naturally across a wide range in Queensland and the Northern Territory, usually in open forest and sometimes in monsoon forest and vine thickets.

Photo: Russell Cumming

The foliage is helpful for identifying Bursaria incana when not in flower. The leaves (photo above) appear to be arranged in alternate clumps along the twigs and the leaf blades have pale-coloured undersides covered in fine matted hairs. Seedlings and young Bursaria incana plants have tiny sharp spines in the leaf axils (approach with care!) but the spines are lost as the plant matures.

Photo: Russell Cumming

In young specimens the bark is pale grey and fairly smooth but older Bursaria incana develop rough, dark grey bark (photo above).

Photo: Russell Cumming

The flowers (seen close-up above) produce distinctive flattened, purse-shaped capsules (photo below) that gradually change from pale green to brown as they mature. Inside these capsules are flat brown seeds that usually germinate fairly easily.

Photo: Russell Cumming

Plant of the month 02/2024: Euphorbia bifida

Photo: Julia Hazel

Now, after good rains in our region, is the best time of year to spot Euphorbia bifida with its clusters of tiny white flowers* sparkling amongst tangled grasses and other back-beach vegetation (photo below).

Photo: Russell Cumming

Euphorbia bifida (Euphorbiaceae) is widely distributed near the coast in Queensland and beyond, but being small and low-growing, it is very inconspicuous when it is not flowering.

Photo: Julia Hazel

Euphorbia bifida can be propagated fairly easily from cuttings and makes an attractive addition to a well-watered planter box (photo above) or sunny garden. Despite growing naturally in sandy coastal dunes, where it survives extreme heat and dryness, most Euphorbia bifida plants in cultivation seem intolerant of prolonged dry periods. Possibly this is because our cutting-grown plants never develop the deep, tough roots of natural seed-grown Euphorbia bifida.

Photo: Julia Hazel

*Viewed very closely, the floral parts of our PoM (photo above) hint at something that serious botanists understand – these are not ordinary flowers! What most of us happily call “flowers” on Euphorbia bifida and other Euphorbiaceae, are actually more complex structures. They are correctly called ‘cyathia’ (singular: cyathium). You can do an online search for cyathium details if you’d like to explore this botanical rabbit-hole!

Plant of the month 01/2024: Carallia brachiata

Photo: Julia Hazel

Carallia brachiata is not a rare species in our area but it can be easily overlooked amongst dense creek-bank vegetation. Fortunately it’s often ‘flagged’ by a bright yellow caterpillar poised conspicuously on a dark green leaf (photo above). These distinctive caterpillars of the Four o’clock Moth Dysphania numana rarely feed on other trees, so they are a convenient aid for identifying Carallia brachiata.

During NPQ outings to Cleveland Creek we’ve seen Carallia brachiata (Rhizophoraceae) as a small tree, both along the upstream section of the creek and downstream. However, as its common name Freshwater Mangrove suggests, this species doesn’t extend into the inter-tidal zone. And in less crowded situations, Carallia brachiata grows taller and develops a fine shady canopy like this specimen in Cairns (photo below).

Photo: Russell Cumming

Carallia brachiata has oval leaves that are glossy dark green on the upper side and dull light green underneath (photo below).

Photo: Russell Cumming

Carallia brachiata produces clusters of small greenish-cream flowers (photo below) that develop into globular red fruits (photo second below) relished by many birds.

Photo: Russell Cumming
Photo: Russell Cumming

Plant of the month 10/2023: Crateva religiosa

Photo: John Elliott

Crateva religiosa, an unusual member of the Caper family, is little known in Townsville although a few plant enthusiasts have grown it successfully here. One of our members has a fine specimen doing very well in his garden (photo below) and it is currently in flower (photo above).
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Photo: John Elliott

Crateva religiosa (Capparaceae) grows naturally in Cape York and the Northern Territory and also occurs across Southeast Asia and islands in the Pacific. It has long been considered a sacred tree and planted near temples, as reflected in its species name. In ideal situations it can reach 15 metres but it is much smaller in drier areas. In gardens it can be easily pruned if necessary, as the wood is very soft.

Photo: Russell Cumming

Crateva religiosa may be briefly deciduous at the height of the dry season, before putting out bright green trifoliate leaves and showy delicate flowers in terminal corymbs (photo above). The petals start out white and fade to yellow (photo below).

Photo: Brian Venables

The fruits of Crateva religiosa (photo below) are large with a leathery surface containing numerous seeds in cream flesh. Some people notice a smell of rockmelon on opening these fruits, others find it musky or even nauseating (perhaps depending on the degree of ripening?). The fruits are relished by native mammals and considered edible but not palatable for humans.

Photo courtesy Atlas of Living Australia CC-BY 3.0, for details see:
https://bie.ala.org.au/species/https://id.biodiversity.org.au/taxon/apni/51269947#overview

Plant of the month 09/2023: Dischidia major

Photo: Russell Cumming

Dischidia major (Apocynaceae) is a strange-looking tropical plant, native to Queensland (Cape York) and also occuring in some Asian countries. It naturally grows as an epiphyte, twining around tree trunks and branches, as in the photos above and below.

Photo: Greg Calvert

Dischidia major , sometimes called “Rattle Skulls”, has the unusual habit of bearing two distinct types of leaves at the same time. It has small, almost circular leaves growing in opposite pairs, widely spaced along its twining stems. It also has dense clusters of large, hollow, tongue-shaped leaves.

Photo: Julia Hazel

At our NPQ Townsville meeting this month, we had a close look at a potted Dischidia major grown by one of our members. We discovered each hollow leaf has an almost-hidden entrance at its base, marked by the arrow in the photo above. So what was inside? We cut open a leaf to find out – photo below.

Photo: Greg Calvert

This leaf was empty, except for roots emerging near the petiole and spreading inside the hollow leaf. However, researchers have found wild-growing Dischidia major plants typically have certain species of arboreal ants nesting in their hollow leaves. Apparently the ants benefit from a secure shelter and their waste accumulates inside the leaf together with condensed moisture.

As an epiphyte, Dischidia major does not have the opportunity to absorb nutrients from the earth. However, when it hosts resident ants, their waste creates a small private compost heap in each occupied leaf, from which the plant’s interior roots take up nutrients – a very neat symbiosis!

In cultivation Dischidia major needs very good drainage (a chunky orchid mix is suitable) and intermittent watering. Provided the plant has a sheltered spot with bright indirect light, it grows well in Townsville even though there may be no ants of the right species to occupy its leaves. The plant brought to our meeting even had flowers emerging from its twining stem (photo above, left side above the rim of the pot).

Botanical details are available at https://apps.lucidcentral.org/rainforest/text/entities/dischidia_major.htm