ACACIAS VHT114

Wattles can be grown for a range or amenity purposes (eg. land rehabilitation, decorative garden plants, windbreaks etc), timber production, a cut flower, for tanning, as a food (bush tucker plant), etc.

Their flowers are small, grouped in large numbers to create round balls or cylindrical spikes. These balls or spikes normally occur on peduncles (ie: a ball or a cylinder on the end of a stalk). They occur either singly, in pairs or racemes emerging from the axils of the leaves or phyllodes. The tiny flowers each have 4 to 5 sepals, 4 to 5 petals and numerous staemens. The fruit is a leguminous pod, often long. When mature, the pod will open releasing large hard coated seeds from inside.
In most species, there are no leaves. Instead, the plant has leaf like structures (considered to be modified petioles or leaf stalks), called "phyllodes" .

COURSE CONTENT

There are eight lessons, as outlined below:

1. Introduction and Resources.

• Nature and Scope of Acacias
• Plant/Acacia Taxonomy (classification and naming)
• Acacia Ecosystems
• Significant Acacias from Australia, Africa and the Middle East

2. Physiology and Botany of Acacias.

• Acacia relatives; and the Order Fabales
• Understanding flower structure of Acacias
• An inflorescence
• Using Botanical terms to describe Acacias
• Acacia foliage
• Classifying Acacias according to foliage type
• Classifying Acacias according to flower type
• Acacia fruits (seed pods)

3. Culture

• Environmental considerations
• Nutrition
• Pest and Disease
• Soil conditions for Acacias
• Typical cultural requirements
• Australian Acacias (review of size, foliage and flowering)
• Weed management
• Soil testing

4. Propagation

• Scope of wattle propagation
• Seed treaments
• Sowing wattle seeds
• Seed storage
• Acacia cutting propagation
• Transplanting seedlings or cuttings
• Potting up

5. Acacias And Their Uses

• As a landscape plant (windbreaks, screens, shrubberies, erosion control, soil enrichment, rock gardens, tubs)
• Plant selection
• Buying the right specimin
• Using Acasias as specimin trees
• Garden Design with Acacias
• Creating landscape affects
• Acacia species for different conditions

6. Other Uses For Acacias

• Timber
• Tanning
• Cut Flowers
• Perfumery with Acacias
• Acacias for human food
• Acacias for animal fodder
• Gum Arabic

7. Pest & Disease of Acacias

• Nature and scope of Pest and Disease
• Pest and Disease problems detected on Acacias
• Environmental problems

8. Special Project
Problem Based Learning style project, to plan the establishment of a collection of Acacias for a specific location.

AIMS

• Describe the way in which Acacias are classified.
• Determine how to find reliable resource information that relates to Acacias
• Describe the physiology of Acacias
• Determine cultural requirements that are common to Acacias
• Determine propagation methods that are commonly applicable to Acacias.
• Describe a variety of commercial uses for Acacias.
• Describe a range of other practical uses for Acacias.
• Identify and recommend treatment for a variety of health problems occurring with Acacias.
• Develop an in depth understanding of one aspect of Acacia Growing.

DURATION: Approx. 100 hours

Extract from Course:

Floral Structure of Acacia

Acacia flowers are small, grouped in large numbers to create round balls or cylindrical spikes. These balls or spikes normally occur on peduncles (ie: a ball or a cylinder on the end of a stalk). They occur either singly, in pairs or racemes emerging from the axils of the leaves or phyllodes. The tiny flowers each have 4 to 5 sepals, 4 to 5 petals and numerous staemens. The ovary is superior (ie: The ovary sits above the base of the petals in the flower). The fruit is a leguminous pod, often long. When mature, the pod will open releasing large hard coated seeds from inside.

Foliage

In most species, there are no leaves. Instead, the plant has leaf like structures (considered to be modified petioles or leaf stalks), called "phyllodes". In some species there are true, bipinnate leaves. In the species which have phyllodes, there are true bipinnate leaves at the seedling stage; however these disappear and are replaced by the phyllodes very early on. Two types of glands or swellings can also occur on the foliage:

• At the base of the phyllode or bipinnate leaf there can be a bump or swelling. This is called a "pulvinus". It is involved in movement of the foliage in response to various stimuli such as dark, light, wind etc. This can cause the leaf or phyllode to move into a position which will minimize water loss in high wind or maximize exposure to light for photosynthesis.

• Circular markings or bumps on the margins of a phyllode or on the petiole of a bipinnate leaf are "extra floral nectary glands". The number and arrangement of these is often used as a distinguishing factor in identifying to similar species.

Classifying Acacias according to Foliage Type

There are two main groups:

1. Where bipinnate foliage is present on the mature plant.

eg: Acacia baileyana, botrycephala, mitchellii

2. Where the mature plant has phyllodes only.

The following is NOT a comprehensive listing of the alternatives:

a/ Lanceolate phyllodes.  eg: Acacia rubida

b/ Sickle shaped phyllodes  eg: Acacia acinaceae, pravissima

c/ Elliptical phyllodes   eg: Acacia pycnantha

d/ Cylindrical phyllodes  eg: Acacia colletioides, rigens, enterocarpa.

e/ Veins two or more on flat phyllodes   eg: Acacia howittii, verniciflua, implexa, melanoxylon

f/ Phyllodes normally Absent   eg: In Acacia spinescens, the branches are rigid spiny, and phyllodes are generally rare when they do occur they are narrow and approx. 1 inch long.

g/ Phyllodes Decurrent  This means the phyllodes extend down the stem, forming a sheath around part of the stem. eg: Acacia triptera, continua etc.

Classifying Acacias according to Flower Type

There are two main groupings.

1. Ball Flowers

a/ Flowers on a Single Peduncle   eg: Acacia acinaceae, rotundifolia, stricta, brownii

b/ Flowers occur in Racemes   eg: Acacia buxifolia, myrtifolia, pycnantha, decurrens, dealbata

2. Cylinder Flowers    Note: The groupings below are not comprehensive.

a/ Flowers on a Single Peduncle or in Pairs    eg: Acacia floribunda

b/ Flowers in on Individual Stalks in groups of 1, 2 or 3   eg: Acacia grasbyi

c/ Flowers Two or more on a Common Stalk    eg: Acacia lepostachya

Acacia Fruits (Seed Pods)

These are variable and can be an strong indicator when differentiating species.

They can vary in terms of:

• Colour -Depending on the species the mature pod may have shades of white, red, purple, brown or bright green, etc
• Size -some species are relatively small and others large; though the size can also be influenced by the plant's vigour
• Surface -some pods have a rough surface, while many others are smooth
• Markings -some pods are strongly veined, others are not
• Shape -Though all are pods, there can be a huge variation with different species having different shapes. Some are an even shape (similar to a pea pod), while others are deeply undulate (like a series of circles each connected by a narrow bridge. Some are coiled or recurved (curved at the end), while others are not

If collecting or photographing specimens for later identification, pay attention to the pods as well as other plant parts.

Some species tend to open and drop seeds on the ground below the trees as soon as they are ripe; while others can be held inside an unopened pod for months

Pods that remain unopened for a while (eg. A. ligulata and A. Cyclops) that also have bright coloured seed stalks are thought to attract birds that may collect pods (for nests) and help distribute the seed elsewhere. Ants are also known to collect seed and carry them underground for storage.

Some seeds can remain viable for very decades.

Acacia seeds may sometimes germinate soon after falling to the ground; but some seeds may lay on the ground, viable, without germinating until conditions are favourable.

Fire or rain will often stimulate germination.

• Fire can do this by cracking a hard seed coat to allow moisture to penetrate and start the germination
• Rain can do this by softening the seed coat; or even reacting with organic matter on the ground to produce a mild acid that could penetrate the seed coat.

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Marie Beerman  B.Sc., M.Hort.