Boronia denticulata

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Boronia denticulata

There are many Boronia spp. in WA growing in a variety of habitats, Boronia denticulata likes wet feet and is often found growing in water up to 20 cm (8”) deep. Locally it favours the outer parimeter of freshwater swamps, which fill in winter/spring and slowly drain during summer/autumn, which although evaporation would be an influencing factor, the slow seepage through the non-calcareous sandy/peat soil, over a clay substrate would be the main reason.

Other than a few large Melaleucas, the other vegetation in outer portions of these swamps are sedges to around a metre (3’) in height, which means the growth of this Boronia tends to be slender to 2 metres (6’-7’) in order to reach over them. During bushfires all will be burnt in this sedge environment, especially when dried out in summer (although probably moisture remains below the surface), however Boronia denticulata will commonly sprout from its rootstock at the first sign of rain.

The attractive pink flowers are arranged in elongated terminal clusters but due to the weakness of their support, they tend to flop in an untidy manner, although this might not be typical of plants in more exposed environments. The flowers that are a little over a centimetre (1/2”) diameter are quite sturdy and will last for lengthy periods. The foliage is quite variable over its range, although locally they are mostly finely toothed (dentate) and linear to oblanceolate to 3cm (11/4”) in length, with the younger plants having the broader leaves.

Depending on weather conditions, Boronia denticulata can usually be found in flower, particularly in years of above average rainfall and has been recorded from July to February. Distribution is scattered in near coastal areas containing suitable habitat, which is mainly around Albany, Bremer Bay and Esperance.

Boronia is part of the Rutaceae family, which contains many ornamental plants, plus the commercially important citrus species.

Boronia spathulata – Rutaceae

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Boronia spathulata – Rutaceae

Boronia spathulata is another attractive member of the Rutaceae family and grows in a variety of habitats from the east of Esperance at Israelite Bay to spread westwards as far as Perth. It is particularly common in low-lying areas around the coast and inland as far as the mallee region, growing in deep or shallow sand, sometimes over gravel or limestone.

Growth habit is highly variable, from a few lanky stems to quite compact bushy shrubs. However age may be a factor in the development of stems, as these reasonably long-lived plants readily resprout from the base if it dies back during a hot summer or is otherwise damaged. It is recorded growing to a metre (3’), but locally it is mostly less than half this in height.

Flowers grow to 2 cm (3/4”) diameter and mostly in shades of pink (some very deep) although occasionally white. Being large and bright they stand out in their preferred sparsely vegetated habitat, like roadsides, after fires or disturbed areas. The fleshy flowers will bloom for several weeks and plants can be in flower for most of the year providing sufficient warmth and moisture is available.

Desert Boronia - Boronia inornata

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Desert Boronia - Boronia inornata

Although called the Desert Boronia, it is small shrub most common in mallee shrubland, which may have a low and irregular rainfall, but is certainly not a desert. Its preferred mallee habitat is a fine sand/clay loam over limestone, it also grows around salt-lakes and loams over limestone closer to the coast. Besides being one of the most floriferous boronias, it is also one of the most common, occurring in huge carpeting numbers on disturbed soil and after bushfires. You could say Boronia inornata is a colonising plant, helping to stabilise soils in low rainfall areas until larger plants can develop and take over. As this transition takes place, the boronias gradually die off, leaving only those in small openings amongst taller vegetation. However, these boronias now sheltered in a semi-shaded environment are to my mind more attractive by showing off a greener (round and warty) foliage and exhibiting a wider range of delicate pink flowers.

In exposed areas the Desert Boronia seldom exceed 300 mm (12"), but can grow closer to a metre (3') in more sheltered locations. It is not only a pretty plant, but a long flowering one too, often blooming profusely from May to December, but flowers can invariably be found at other times after rainfall. The blossom attracts a large variety of flying insects that no doubt take care of the pollination.