Acacia sp. in Black Hill, Morialta and Horsnell Gully Conservation Parks
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.
- Acacia acinacea
- Acacia continua
- Acacia cupularis
- Acacia dodonaefolia
- Acacia ligulata
- Acacia melanoxylon
- Acacia myrtifolia var. myrtifolia
- Acacia paradoxa
- Acacia pycnantha
- Acacia retinoides var. retinoides (hills form)
- Acacia spinescens
- Acacia rupicola
- Acacia victoriae
Black Hill Conservation Park
photo from August 2002.
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. This species 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.
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 responseThis 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.
Black Hill Conservation Park
Wildflower garden July 2006.
October 2005. Black Hill Conservation Park
A rounded shrub about 2 metres by 2 metres.
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 cupularis June 2009.
Black Hill Conservation Park
photo from 1999.
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.
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.
New photos added, minor formatting changes 8 May 2018
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