Jacksonia venosa – Fabaceae

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Jacksonia venosa – Fabaceae

Jacksonia is one of the many peaflower genera from the legume Fabaceae family, which now also includes Acacia, Senna, etc. Jacksonia venosa is a small shrub mostly between 10-20 cm (4”-8”) in height and spreading to 60 cm (2’) diameter. It is very common in near coastal locations from Ravensthorpe to Israelite Bay, with Esperance centrally placed between.

There are several similar looking Jacksonia plants in the district, but Jacksonia venosa is easily distinguished by their relatively near coastal distribution and the flowers, which are strongly veined red on the back of the standard. It normally grows in a heath environment on a variety of non-calcareous sand and/or gravel soils.

Jacksonia as a group, are usually easily placed in the genus by the long sepals, which are mostly strongly reflexed to point away from the flower. Also many are leafless and some have flattened stems. The flowers are invariably yellow and orange, merging to red. Once two or three species have been seen, others can be slotted with little effort, although taking them to species level can be tricky.

Several Jacksonia spp. are very opportunistic regarding unseasonal rainfall, by quickly coming into flower to take advantage of a good soaking, so often flowers can be found during a wet summer, although not as numerous as from August to October, which is their main flowering period.

Jacksonia viscosa

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Jacksonia viscosa

An unusual looking shrub with forked broom-like stems and large bright yellow flowers with red markings on the floral standard. You would think that a shrub (to 2 metres or over 6', but more often half that size) and apparently leafless, would blend into the mass of vegetation types common to heathland of the highly floriferous southern region of Western Australia, but it does not and this may be due to its neat home garden like shape. Another difference to most other plants in this environment are the stems, which are termed cladodes. These are like flattened stems that function fully as a leaf, but the true leaves are little more than scales at the base of each cladode.

Jacksonia viscosa is a common species favouring the moist but well-drained heavier soils (which may be overlain with sand) of near coastal heathland. They often occur in quite large colonies, but cease abruptly when the soil-type or drainage change, so there are large areas where they do not occur at all, as their preferred growing conditions are somewhat patchy in the region. The flowers are around 2 cm (3/4") in length, but appear larger as the petals either side of the keel grow outwards, giving it a chunky look when compared with most other pea-flowers whose side petals tend to hug the keel, thereby placing greater visual emphasis on the standard alone.

A long flowering shrub and flowers can usually be found at most times, although they mainly bloom after rain during the warmer weather, so spring/early summer, and again late summer/autumn would be the best time to view them.