Walkers wandering through their favourite woodland patches throughout the year, mostly pass Bursaria spinosa or "Sweet Bursaria" without giving it a second glance. However, around Christmas time, when the woodland's spring flower colour parade is but a withering memory, it tends to attract their attention. This is a response to its sweet "pittosporum" like scent and the attractive panicles of small star like white flowers blanketing the bushes. The botanical inquisitiveness of the walkers is subsequently prompted enough to engage in a closer inspection. This often leads to the muttering of the name"Christmas Bush" amongst the group.
Commonly at this point, little further interest is shown. Consequently, the profusion of insect and bird life humming around these plants remains undisturbed, as the walkers continue on their merry way, decidedly disinterested in any further examples of this "take it for granted" shrub.
The following summary explores some of the reasons why this shrub should be considered anything but uninteresting!
Its abundance across southern Australia has resulted in a variety of common names. These include "Christmas Bush" and "Sweet Bursaria" which were discussed earlier.
However the names, "Blackthorn" and "Prickly Box" were initially used by the early graziers, who were frustrated by its persistence in snagging the wool of passing sheep or bloodying browsing cattle with its sharp spines. The name "Native Box" relates to colonial pastoralists using it as a hedging plant often as a substitute to the more sinister invasive weed species "Boxthorn" (Lycium ferosissima).
"Boxwood" is another common name, which has been applied to the small tree specimens of this plant, because not only do they have an attractive box-like bark, but they also provide a source of quality, attractively figured, craft wood.
"Bursaria" derives from the Greek word "bursa". This word was used to describe a sack, pouch or purse-like structure. The applicability of this word to this plant is obvious, given the many purse like seed capsules that are prominently displayed from late summer onwards.
Children are intrigued when they can relate this plant to the professions of "Ship's Bursar or School's Bursar". They are often amused with the knowledge that these jobs relate to this botanical name. The implication is that these positions control the "purse" or the financial matters, for a boat or a school respectively.
"Spinosa" refers to the spiny/thorny nature of the most common subspecies, namely Bursaria spinosa var spinosa, which is typically located in harsher conditions. Bursaria spinosa var macrophylla is a broader leaved, non-spiny subspecies growing in moister less demanding woodland environments.
English and Californian horticulturalists have landscaped with "Sweet Bursaria" for more than a hundred years, describing it as "charming" and "delightful".This is in recognition of its pleasant summer floral display, coupled with its handsome tessellated box-like bark.
These attributes make it a useful specimen plant or alternatively, a hedging plant. A row of closely planted "Bursaria" seedlings will produce an impenetrable formal hedge, if regularly clipped. A natural, taller and more open hedge results if they are allowed to grow unchecked. This informal hedge provides excellent bird nesting sites and spider web locations.
Indigenous plantings of "Bursaria" can perform "anti-personnel' functions. Their spiny nature directs pedestrian movement in the landscape, assists in minimising the vandalism of new plantings and protects the native feathered and fury creatures from marauding domestic pets.
Following weeding of the vicious "boxthorn" weed that is often located in open paddocks and grassy communities, "Bursaria" has proven to be the ideal replacement plant. Its tight, spiny form, similar to "boxthorn", provides a reasonable habitat substitute for the many creatures that would have adapted to the earlier protection offered by the "boxthorn" bushes.
Sheep and cattle browsing in degraded woodland communities (bush runs), cause the demise of many native shrubs, herbs, grasses and groundcovers. This is a consequence of the persistent grazing not only of the native understorey plant's foliage but also their young succulent seedlings that may have germinated.
Depending on the stocking rates and how long the grazing continues unabated, the ecological values of the woodland community may diminish rapidly.
Just prior to the stage when natural regeneration loses its ability to heal the land, the degradation signs are typically, browsed "Bursaria" shrubs standing as solitary sentinels amongst a plethora of introduced pasture weeds and erosion scars.
However, all is not lost! With a little education and attitudinal change by the land manager, accompanied by an effective stock control fence, installed after the de-stocking of the bush run, natural regeneration can begin to operate to restore the original woodland community.
Important in this natural regeneration process, is the role of the tolerant "Bursaria" remnants. These not only provide critical habitat for the re colonisation by insects and birds, but also provide a protective framework for young native seedlings to germinate and grow from the native seed stored in the soil.
Each "Bursaria" bush offers a nectar and larval food source for birds, beetles, butterflies, moths, wasps, bees, ants, etc. This in turn, allows pollination, seed dispersal and nutrient cycling processes to be initiated. These are the building blocks for successful natural regeneration of degraded woodland communities.
Hill topping sites have recently been recognised for their role as foci for mating of butterflies. They provide sites, proud of the lower sea of exotic pastures, for butterfly mating. This mating process brings together a mixture of genetic material from sparse and frequently isolated butterfly populations.
These degraded rocky outcrop remnants, often consist of only a framework of hardy Acacia spp. and "Bursaria" trees and shrubs along with a few species of native grasses, sedges and groundcovers. However, degraded as they are, they still provide a stable set of physical and botanical features recognisable sufficiently enough by the male butterflies, that they will comfortably use these sites to attract passing females for mating.
This stability is essential, as the male butterflies will otherwise abandon these sites, following substantial changes to the site's vegetation.
Local butterfly extinctions and the subsequent loss of pollinators for local provenance plants are the result.
This butterfly relies on "Bursaria" for its larval food. It is often seen in the upper suburbs of Hobart or on these "hill-topping" sites, following the pupation of its caterpillars.
This butterfly has a symbiotic relationship with black ants that attend its caterpillars protecting them from predators, in exchange for their honey-like fluid secretions.
"Bursaria" bushes provide an intricate architecture of thorns and twiggy foliage, which is much sort after by numerous species of spiders for constructing their webs.
When the bushes are flowering, their sweet nectar attracts a myriad of insects, only to be entrapped in these 3 dimensional spider snares.
These spider webs also have an important role in attracting a diversity of indigenous birds.
In order for successful nest building to be completed by a number of our native birds, such as Grey Fantails, Crescent, Black Headed and New Holland Honeyeaters, Tasmanian and Brown Thornbills, all our Robins etc, they are reliant on the collection of spider web spinnings to knit their nests together.
Bursaria not only offers a safe location for nest building, but also supplies source of essential ingredients.
The glycoside named Aesculin found only in sufficiently high concentrations within the leaves of "Bursaria" proved very important to the World War 2 military forces.
Originally, before the W.W. 2, Aesculin was only extracted in very low concentrations from the bark of the English "Horse Chestnut "trees (Aesculus hippocastaneum) following the felling of the tree. This destructive process was curtailed when it was discovered that this active agent could be extracted from the dried "Bursaria" leaves, after hammer milling and solvent extraction.
Aesculin provided the active ingredient for a sun screening lotion. This relieved the sunburn problem particularly for the fully exposed turret gunners of the W.W.2 Bombers.
It also proved a valuable bacteriological reagent in the testing for tropical diseases for Australian Forces in the tropical theatres of war.
An associated use was for effective treatment of blood vessel disorders of our servicemen including it use as an agent to manage haemorrhoids.
In summary, for the many reasons discussed, it does earn its place in any woodland revegetation project. It also has enough stories for memories to reflect on that it may be worth more than a second glance particularly if it is in flower.
Phil Watson