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Philotheca salsolifolia

Wax flower

Family: Rutaceae

Philotheca salsolifolia is a shrub to 2 metres tall with about a 1-metre spread and hairless branchlets.

It is naturally and only just confined to New South Wales (although there is one single record in Queensland), growing in the north from near Bonalbo, south along the coast, tablelands and western slopes, as far west as West Wyalong, to north-west of Bega.

It is typically found on sandy soils and sandstone, in rocky areas, in heath, shrubland and dry sclerophyll woodland and forest.

Philotheca spp. have simple and alternate leaves (a trait it shares with its relative Citrus), often with conspicuous oil glands and odorous.
In this species, the leaves are crowded to well-spaced, linear to tubular (terete) to 15 mm long, dotted with oil glands on the underside, and are aromatic.

Philotheca spp. produce flowers in leaf axils or at the terminals, often reduced to single flowers with leaves in-between or in cymose or racemose groups. Flowers have 5 sepals (rarely 4) and 5 petals (rarely 4).
In this species, flowers are arranged singly or in 2s or 3s, mostly at branch terminals, with petals pink to mauve with a dark central stripe, about 30 mm across, occurring mainly in spring.

The fruit of Philotheca is a schizocarp-capsule – which splits into equal segments on maturity which each segment called a coccus (plural cocci). In this species, the cocci are oblong, to 6 mm long.

In the garden

Not much is known about the cultivation of this species and it is not widely grown.

It may be difficult to cultivate or may need more application. It may be available for cultivation in the future. Check with local native nurseries.

Philothecas can be challenging to grow but often with more success than the related Boronias. They are very attractive in flower and well worth the effort.

In a garden situation it grows best in a well-drained soils in full sun. They can succumb quickly to poor drainage. Place in a well-drained sandy soil, in semi-shade to full sun, preferably on a slope. Lightly prune after flowering to maintain compact shape. Flowers attract bees and butterflies.

Very useful in rockeries and sloping gardens.

Propagation

In common with most members of the Rutaceae, propagation from seed is difficult. Cuttings usually strike readily from current season’s growth but some species can be slow to form roots.

Other information

There are two subspecies accepted by the Australian Plant Census which are also accepted in NSW:
Philotheca salsolifolia subsp. pedicellata has thin pedicels to 9 mm long and leaves to 15 mm long, occurring only on the North Coast subdivision of NSW;
Philotheca salsolifolia subsp. salsolifolia has top-shaped pedicels to 2 mm long and leaves to 5 mm long, occurring over the rest of the range.

Very similar to P. reichenbachii which occurs over the same area although has a much smaller range. This editor has learnt from other botanists that the two species can be easily confused.
In this species, the anthers are not concealed by the hairs on the upper parts of filaments and, in addition, the anthers do not have apical tufts of hairs; whereas anthers have apical tufts and the filaments also have long hairs reaching the anthers in P. reichenbachii.
The leaves of P. reichenbachii are strongly glandular-punctate (dotted) but much less so in P. salsolifolia.

Philotheca is a genus of about fifty species, all are endemic to Australia with species in every state except the Northern Territory.
Many plants formerly in Eriostemon are now in this genus.
See this link: https://en.wikipedia.org/wiki/Philotheca#cite_note-11 for a list of Philotheca species accepted by the Australian Plant Census as at April 2019.

Most Philotheca plants would die in a fire and regenerate from the seedbank.

Philotheca – was first described by Edward Rudge in 1812. As there are some reported variations on the meaning – the Latin of Rudge was transcribed for these profiles as follows: all as in Eriostemone, but the habit is very different from that of the ericoid branches; The terminal flowers and the filaments below, enlarged into the naked box, whence the name.
It has been reported that Psilos (ψιλός) refers to “naked” or “bare” in Ancient Greek. Philos (φίλος) in Greek tends to mean “friend”. Philia (φιλία) in Ancient Greek means “highest form of love”
The suffix -theca refers to “box” or “case” in Ancient Greek.
Hence, it is thought the name means “naked-box” or “loving-box” referring to the condition of the 10 (or 8) stamens that are fused at the base and forming a box-like structure. (Note: this is not the case in all species with some having free stamens).

salsolifolia – Latin – having leaves like Salsola – a genus of cosmopolitan saltbushes in the Chenopodiaceae family.

This species is not considered to be at risk of extinction in the wild.

Australian Plants Society – Sutherland Coastal Plants CD Resources – Philotheca salsolifolia profile page
https://sutherland.austplants.com.au/rnp/pl171.htm

NSW Flora Online (PlantNET) – Philotheca salsolifolia profile page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Philotheca~salsolifolia

Wikipedia – Philotheca salsolifolia profile page
https://en.wikipedia.org/wiki/Philotheca_salsolifolia

By Jeff Howes, edited Dan Clarke