A shrub to 2.5 metres high with smooth, round stems, spreading to 1 metre wide.
It has a restricted distribution, growing in crevices of granite boulders on the northern tablelands of NSW, north from Armidale though Glen Innes and Tenterfield, with most records in Queensland, just north of Jennings on the border.
It grows in tablelands heath and shrublands.
Leionema spp. have characteristics matching those of other similar Rutaceae genera, eg: Philotheca, Phebalium, Crowea; i.e. simple, alternate leaves, usually with oil glands.
In this species, leaves are flat, ovate to elliptic-oblong to obovate, to 10 cm long and 4 cm wide, dark green and hairless, with the base conspicuously clasping the stem, with rounded basal lobes.
Leionema spp. have 5-merous flowers; i.e. 5 sepals, 5 petals and usually 10 stamens surrounding 5 carpels, with an overall attractive star-shaped appearance. Flowers can be produced in leaf axils or branch terminals, in cymose clusters or solitary.
In this species, flowers are produced in terminal clusters of cymes, with up to 200 flowers per cluster, with flowers about 10 mm across, white in colour, appearing in spring to summer.
The fruit of Leionema is a schizocarp-capsule – which splits into equal segments on maturity which each segment called a coccus (plural cocci).
The capsule is approximately 3 mm long.
This species is not widely known to be cultivated. It may be difficult to grow or may not have been trialled sufficiently. Check with local native nurseries for availability.
In cultivation, Leionema spp. prefer well drained (sandy to sandy loams), acidic soils in dappled shade or morning-light positions. They are highly-drought tolerant once established but benefit from some supplementary watering. It is advised to add some slow-release fertiliser when first planted and they will benefit from periodic organic fertilising (eg: blood and bone or seaweed solution).
It has been reported that species in this genus should be cultivated more widely and simply need more attention and effort (see Australian Native Plants Society Australia weblink in the references).
In common with most members of the Rutaceae, propagation from seed is difficult but cuttings usually strike readily.
Leionema are a genus of 28 known species, 27 of which are endemic to Australia, with 1 species endemic to New Zealand. These species have been previously classified in the genus Eriostemon and Phebalium.
Leionema differs by not having anthers with an apical point or gland, as well as free sepals on the flowers and small bracteoles on the middle to upper part of flower stalks (pedicels).
Most Leionema spp. would likely die in a fire and regenerate from seed. Some basal regrowth or stem-reshooting may be possible.
Leionema – from Greek leios (λείος), meaning “smooth”, and nema (nήμα), a thread, referring to a ‘hilar strand’; a small piece of tissue joining the hilum (a scar on the side of the seed) to the ovule.
ambiens – Latin meaning “going around” or “surround” – referring to the manner in which the base of the leaves clasp the stem.
This species is not considered to be at risk in the wild but has a restricted distribution and is considered rare.
NSW Flora Online (PlantNET) – Leionema ambiens profile page
Australian Native Plants Society Australia – Poor Relations – Phebalium / Leionema / Nematolepis