As a boy I remember itinerent flower sellers coming to our house with bunches of heavenly smelling Boronia metastigma. I recently learnt that the intense aroma is a strategy to attract a particular pollinator - a heliozelid moth. The moth pollinates the flower while laying eggs on the carpels (ovaries). Caterpillars eat some but not all ovaries, so win win for plant and moth.
Boronias are in the Rutaceae family, which is characterised by open flowers with a superior ovary and leaves containing oil glands.Our domesticated citrus plants are in this family.
Boronias have opposite leaves and four sepals and petals.
Recently Boronias have been split into two genera:- Boronia and Cyanothamnus. There is almost no physical difference between the genera. Two different genetic groups have evolved very similar plant features. A trifle perplexing for the amateur, but such is modern taxonomy.
Boronias are in the Rutaceae family, which is characterised by open flowers with a superior ovary and leaves containing oil glands.Our domesticated citrus plants are in this family.
Boronias have opposite leaves and four sepals and petals.
Recently Boronias have been split into two genera:- Boronia and Cyanothamnus. There is almost no physical difference between the genera. Two different genetic groups have evolved very similar plant features. A trifle perplexing for the amateur, but such is modern taxonomy.
When I moved to Narrogin, I was amused to find tiny Cyanothamnus ramosus flowers in Foxes Lair. Local Boronia / Cyanothamnus species are mainly pink/ white or pale blue colours with little scent. Unlike us, Insects see untraviolet light and these colours are exceptionally bright for them. Several native bee species pollinate these boronias.
Male and female parts are clustered together in a tight group. Images of Cyanothamnus ramosus below show that a barrier of serrated stamen filaments with coarse hairs prevent insects from accessing nectar from the side. My guess is that these stop ants and other nectar thieves. To get nectar, insect pollinators have to poke their tongue down the top of the flower past the clustered anthers and stigma. To avoid self pollination, the stigma only becomes receptive after the flower's pollen has died.
Male and female parts are clustered together in a tight group. Images of Cyanothamnus ramosus below show that a barrier of serrated stamen filaments with coarse hairs prevent insects from accessing nectar from the side. My guess is that these stop ants and other nectar thieves. To get nectar, insect pollinators have to poke their tongue down the top of the flower past the clustered anthers and stigma. To avoid self pollination, the stigma only becomes receptive after the flower's pollen has died.
 Cyanothamnus ramosus |  Stamens form a protective rim |  Four - lobed superior ovary |
The dissection of Boronia capitata subsp. capitata shows dense stamen hairs, which exclude nectar thieves.
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There are several mostly pink or white coloured Boronia /Cyanothamnus species in this district.
 Boronia busseliana Wedin reserve |  Boronia crenulata Contine Hill |  Boronia sp. Harrismith reserve |
Two other genera in this district differ from boronias by having alternate leaves and five sepals / petals.
They look very similar.
Asterolasia pallida (white) and squamaligera (yellow) have a tiny or no sepals and petals with a hairy exterior.
Phebalium tubercolosum (white) and filifolium (yellow) are showy shrubs commonly found in mallee woodland in the east of the district. Phebalium sepals are smaller than petals, and the petals have a scaly or scurfy exterior.
They look very similar.
Asterolasia pallida (white) and squamaligera (yellow) have a tiny or no sepals and petals with a hairy exterior.
Phebalium tubercolosum (white) and filifolium (yellow) are showy shrubs commonly found in mallee woodland in the east of the district. Phebalium sepals are smaller than petals, and the petals have a scaly or scurfy exterior.
 Asterolasia squamaligera Dryandra |  Megachile bee on Asterolasia pallida |  Phebalium tubercolosum Harrismith |