Jasminum mesnyi

Jasminum mesnyi.

Primrose or Japanese jasmine is native to Vietnam and southern China.
The erect shrubs, to around 3 m high have long arching cane-like stems.
With any support they become scramblers with stems up to 5 m long.
The 4-angled branchlets have no hairs.

Six of the around 8 species with yellow flowers have alternate leaves while J. mesnyi and J. nudiflorum have opposite leaves like the white flowered species.

The evergreen leaves, up to 10 cm long are on a petiole up to 1.5 cm long.
The blade is divided into 3 leaflets (trifoliate) with only the terminal one on a short petiolule often with the base of the blade running down it.
The ovate, elliptic or oblong leaflets are up to 5 or 6 cm long and 2.5 cm wide.
The rounded tips may have a mucro (a short narrow abrupt point).
The mid to dark green leaflets have a smooth edge and no hairs.
Leaves at the base of the stems may be undivided.

Inflorescences are almost always a solitary axillary flower and rarely a terminal one.
They are on a peduncle up to 8 mm long with leafy bracts to 1 cm long at the base.

The bell-shaped calyx has a basal tube 1 to 1.5 cm long with 6 (4 to 8) green lobes 2 to 5 mm long.
The funnel-shaped corolla has a tube up to 1.5 cm long with 6 ovate lobes up to 2 cm long.
The bright yellow corolla has orange lines in the throat.
In cultivation flowers are mostly semi-double or double with up to 16 lobes in 2 whorls.

There are 2 stamens on short filaments that insert near the top of the corolla tube.
The anthers open inwards through longitudinal slits.
The superior ovary has 2 carpels and a style with 2 stigma lobes that may be separate or lie together.

As the ovules develop the enlarging carpels remain separate apart from their bases which are joined by a short septum.
Mature fruit here are a didymous (paired) blackish-purple berry up to 10 mm long with 1 or 2 seeds in each discrete section.
Frequently one carpel aborts resulting in a spherical berry around 6 mm long.
In either case each section opens into the chamber (loculicidal) starting near the style base and spreading down.

Other yellow jasmines occasionally seen here include Jasminum humile (Italian jasmine with pinnate leaves having up to 7 leaflets), J. nudiflorum (Winter jasmine with trifoliate leaves and flowers on bare stems) and J. parkeri the 60 cm high Dwarf jasmine.