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Philotheca trachyphylla

Rock Wax Flower

Family: Rutaceae

Philotheca trachyphylla is a shrub to a small tree, potentially reaching 7 metres in height but often much smaller.

Most of its natural occurrence is from an area of Morton National Park (between Nowra and Goulburn) in NSW, extending southwards on the coast, close to the tablelands boundary, extending into eastern Victoria (Brythen-Ensay area).

There are also a few records in the regions of Wollongong, Sydney, Lithgow-Bathurst, Broke and Denman.

It is typically found growing in dry and wet sclerophyll forest on hillsides and in moist gullies, often on sandy-rocky soils.

The stems are blue-grey with warty-glands.

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 oblong to elliptic or narrow-obovate, to 50 mm long by up to 10 mm wide and terminating in a short point (mucro), with small warty-glands on the margins and with out a distinct stalk (petiole).

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 in leaf axils with petals white; about 15 mm across and can be produced profusely.

The fruit of Philotheca is a schizocarp-capsule – which splits into equal segments on maturity which each segment called a coccus (plural cocci). The capsule is approximately 5 mm long.

In the garden

This species can be cultivated and has a history of being at least trialled with some success. It is very attractive species producing flowers en masse but despite this, it is not often cultivated, mainly due to difficulties in propagation. Reportedly, it is hardy in a well-drained moist soil in a sunny or semi-shaded position.

It has the potential to grow to over 5 metres but can easily be pruned to be shorter.

This is one of those species where gardeners should keep checking if propagation becomes more successful in the future as this is a very nice plant to have.

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, they grow best in 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. This species is known to be difficult from cuttings as well as seed but worth a try.

Other information

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).

trachyphylla – from Greek trachys (τραχύς) meaning “rough” or “rugged”, and phylla (φύλλα), meaning “leaves”, referring to the warty-glands on the leaves giving them a rough texture.

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

Australian Native Plants Society Australia – Philotheca trachyphylla profile page
http://anpsa.org.au/Philotheca-trachyphylla.html

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

Wikipedia – Philotheca trachyphylla profile page
https://en.wikipedia.org/wiki/Philotheca_trachyphylla

By Jeff Howes, edited Dan Clarke