About Weeds

Introduction

A weed is a plant growing where it is not wanted.

There are many weeds growing along Kedron Brook. Most are non-native plants. Trees like Camphor laurel ( Cinnamomum camphora) and Chinese celtis (Celtis sinensis) were planted in gardens many years ago. Today, birds spread the seed and these germinate in the moist environmental near the Brook. The trees grow into dense thickets that prevent the growth of other plants.

Weeds also change the habitat and food sources available to native fauna.  Replacement of native flora by weeds can result in the loss of a species of fauna from that area of the catchment.

When introduced plants replace the diverse natural communities, they are considered weeds. Many shrubs once occurring in bushland have disappeared from along Kedron Brook. Native plants are replaced by thickets of Lantana ( Lantana camara) in the upper catchment, and by Japanese sunflower (Tithonia diversifolia) and grasses in the middle and lower catchment.

Dense swards of grass occur along many parts of Kedron Brook. Para grass Bracharia mutica is common at the waters edge; Guinea grass (Panicum maximum) and giant Cane grass form some impenetrable stands on the margins of the Brook.

Weed Control

Bushcare groups and Councils undertake weed control along Kedron Brook. The extent of the weed problem is so great, areas and plants treated must be prioritised. We don’t have enough resources to do it all.

Details of weed identification, recording, and prioritisation for removal in relation to legislative requirements and authoritive recommendations are given in a separate web page, Weed Identification and Control Project. Plants routinely targeted for weed control in bush management actives along Kedron Brook are briefly described below.

Madeira vine

Madeira vine (Anredera cordifolia) is an aggressive smothering vine that can grow from just small section of leaves, stems or roots. The vine is common in gardens and bushland in established urban areas. Careful removal of all parts of the plant is required.

Morning Glory

Morning Glory (Ipomoea cairica) is another vine that will smother vegetation; small trees are vulnerable. It has a strong extensive root system from which it will re-shoot if not removed from a site. This vine is widespread in urban areas and is often seen growing over abandoned sheds or other structures.

Singapore Daisy

Singapore Daisy is a spreading herb that readily grows from sections of stem, which are easily dislodged from the parent plant. This plant forms dense mats along sections of Kedron Brook

Chinese celtis

Chinese celtis (Celtis sinensis) is a woody tree; pigeons and other seed-eating birds disperse seeds. This woody weed is well established in many parts of the lower catchment and widespread elsewhere in Brisbane. Maintaining good native tree cover will prevent invasion of this species into bushland, removal of small Chinese celtis before they flower will prevent further spread.

Guinea grass and Para grass

Guinea grass (Panicum maximum) and Para grass (Bracharia mutica) are widespread on land that has been modified and the original vegetation removed. These grasses are typical of such ‘disturbed’ areas. Mechanical control is best in large swards, however this removes potential fauna habitat. The treated area must be replanted and stabilised immediately after grass removal to prevent further weed invasion or erosion.

Japanese sunflower

Japanese sunflower (Tithonia diversifolia) forms dense thickets several metres high. The plant produces many seeds and rapidly colonises new areas. Plant removal prior to flowering will prevent further spread. The Japanese sunflower is not tolerant of very dry periods. Native plants may get an edge on this shrub during drought.

Weeds do have some uses

In many areas, particularly hillslopes and stream banks, the presence of some vegetation (even weeds) is better than bare soil. A vegetation cover on the ground helps protect and bind the soil. Removal of weeds will expose soil to erosion until new vegetation is established.

Weeds can provide habitat for fauna but is not as good as the native flora. Cisticolas are small birds that live in the grassy margins along the stream. Swards of Para grass are used for nesting and hiding, the birds feed on the grass seeds.

Lantana can offer shrubby cover for bandicoots, ground-dwelling birds and reptiles.

In the middle reaches of the Brook, family groups of finches feed on seeds of the herbaceous weed Thickhead (Crassocephalum crepidioides). The finches nest in extensive Para grass stands nearby.

How do weeds get into bushland?

Most of the weeds occurring along Kedron Brook have been introduced from urban gardens. Many weeds flower and seed profusely, or can shoot from parts of the stem. Seeds and stem parts may be washed by stormwater into the Brook, some seed is blown across the landscape on the wind. Birds and bats disperse some weeds but people are probably more important. When soil, machinery and garden clippings are moved weed seeds can hitch a ride. Never dump soil, lawn clippings or other refuse in bushland.

One of the most insidious ways of introducing weeds to bushland is through the dumping of garden refuse. This is material people don’t want in their backyards, it is even less desirable in the local bushland or stream.

Such dumping often occurs near newly developing urban areas or where properties directly abut the stream.

Weeds are here to stay

There are some weeds that may persist in bushland without a detrimental effect on natural ecosystems most of the time.

Where weeds threaten bushland remnants or natural biodiversity, Bushcare groups and others work towards weed removal. An important component of weed removal is replacement of the plants with native plants. This

• helps protect the soil
• provides fauna with resources in the future and
• increases the natural biodiversity of an area

Weed references

First, see the relevant section of our Educational Resources web page.

Weed Identification and Control Project This was a very comprehensive specific project conducted in our major remnant forests along the Brook in 2005-2006 by our BCC Catchment Coordinator, Nathan Kirby.