Acacia sp. in Black Hill, Morialta and Horsnell Gully Conservation Parks

LEGUMINOSAE

This family is familiar to most of us as it includes the edible legumes. It is so large with 650 genera and some 18,000 species that it is divided into sub-families. Acacias fit into the sub-family CAESALPINIOIDEAE.

Found in our Parks are:

Acacia pycnantha
Acacia pycnantha
Black Hill Conservation Park
photo from 1999.

The name Acacia is from the Greek word akakia, acacia, ace or acis (depending on the reference material used) meaning a point or thorn or acazo which means to sharpen. These are references to Acacia arabica, the Egyptian Thorn.

There are a lot of Acacia species, and about 700 in Australia (some of which are not yet described) make Acacia the genus with the most species in the country. Worldwide there are about 1100 species, with Africa having the largest number of species outside of Australia.

These photos show the progression of an acacia sp. seedling. It has true leaves for only a short time

While Acacia leaves are divided into lobes and sub-lobes, few mature plants have true leaves. Mostly the plants have modifified leaf-stalks that take on the role of the leaves. Others lack even these, and the stems act as leaves, these plants are often spiny. Only young seedlings show the true leaves.

Acacias are culturally significant, on 19 April 1984 the Governor-General, Sir Ninian Stevens proclaimed Australia's national colours of green and gold. These colours reflect the colours of the acacia leaves and flowers. Acacia pycnantha is our National floral emblem.

We do have some Acacia species that have become weeds in our Parks. Acacia iteaphylla has been a particular problem in and around the Wildflower Garden, where is was once planted in the ornamental garden. It can also be found in Moriatla Conservation Park. It has adapted well to its new surroundings, being native to the Flinders Ranges, and grows readily from seed, competing with our local native plants. Other problem Acacias are Acacia longifolia and Acacia baileyana. We need to maintain a constant vigil on these plants to prevent them from gaining a hold and changing the local ecosystem which could reduce biodiversity.

Acacia acinacea
Black Hill Conservation Park
Wildflower garden July 2006.

 

Acacia acinacea
wreath wattle, gold dust wattle The name acinacea is from the Latin word acinaces, which is a short Pursian sword. This is a reference to the shape of the leaf-like modified stems.

This is a really pretty small shrub, and one of my favourites. It grows to 1.5 m tall, but usually less, and the very ornamental flowers are held along gracefull arching branches. The leaves have an intersting shape, and new growth can have reddish branches. Seed pods spiral strangley. It is not prickly.

Flowers from May to September.

Fire response

Acacia acinacea
Acacia acinacea
September 2008.

This acacia survives fire through persistance of roots, rhizomes, underground stems, or basal stems, tussock or lignotuber. This vegetatively based surival mechanism means mature plants remain mature, (very rapidly mature with time to maturity less than the primary juvenile period. Juvenile plants die. Adult plants will survive 100% scorch, through root suckers and/or, horizontal rhizomes. Plants which survive 100% scorch, resprout from basal sprouts. However, it is unlikely to populate new areas as it is intolerant of competition from other seedlings, it needs a disturbed site with competition removed and recruits only immediately after a disturbance resulting in a single aged population.
Acacia acinacea
Acacia acinacea
June 2009.

Acacia continua
thorn wattle

Acacia cupularis
cup wattle

Acacia cupularis
Acacia cupularis June 2009.
The name 'cupularis' comes from Latin, and means a litttle cup.

A rounded shrub about 2 metres by 2 metres.

Fire response
This Acacia reponds to fire by germinating from seed. The seeds are long lasting, and not all germinata following a fire event. There is medium confidence that a population of this Acacia species would survive a fire event.

Acacia dodonaefolia
hop-bush wattle

Acacia ligulata
umbrella wattle

Acacia melanoxylon
blackwood

Acacia myrtifolia var. myrtifolia
myrtle wattle

Acacia paradoxa
kangaroo thorn

Acacia pycnantha
golden wattle

Acacia pycnantha
Black Hill Conservation Park
photo from 1999.
The name pycnantha is of Greek origin, Pykos meaning dense, and anthos meaning a flower, and is a reference to the dense flower heads.

This must surely be considered one of our iconic plants. The hills are dotted in golden- yellow late winter as these plants burst into flower. A sure sign that spring is on its way.

Studies have shown that Acacia pycnantha is mainly polinated by birds including honeyeaters, thornbills and silvereyes, which are seeking the nectar excreted from special glands on the phylodes near the flower-heads. Native bees do visit the plants but do not seem to have as great a role in pollination as the birds.

Acacia pycnantha is a food source for the caterpiller stage of several butterflies including Hypochrsops ignita, Jalmenus icilius, Jalmenus lithochroa and Theclinesthes miskini.

These medium sized shrub are usually erect with a central trunk that is very dark brown. In summer, the plants often exude golden gum, that may be chewed to relieve thirst, although initially astringent.

Early in European settlement, the bark from Acacia pycnanth was used for tanning. The leaves are known to dye wool a golden colour when used with an alum mordant.

The plants tend to be rather short lived, but often germinate profously after a fire. In fact the age of the population may be an indicator as to when the area was last burned.

This acacia is one of those which only has true leaves briefly as a seedling. These are very quickly replaced by large flattened leathery phyllodes (modified leaf stalks) which may be up to 20 cm long and 5 to 50 mm wide.

The spherical flowers heads are about a centimetre across, and form along short zig-zag stems.

Fire Response
This species survives fire by germinating from seed after a fire. The seeds have a long life span and will only partially germinate per disturbance, however a 100% scorch may kill in soil propagule storage. There is medium confidence that this species will survive a fire event, and it is described as tolerant of fire events, with a high level of confidence that it will establish after fire.

Acacia retinoides var. retinoides (hills form)
wirilda

Acacia spinescens
spiny wattle

Acacia rupicola
rock wattle

Acacia victoriae
elegant wattle

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New photos added 13 June 2009

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