Meet the weeds

Contributed by Sue Riley

Weeds, what are they?
We all know that some of the loveliest and most appealing plants can become dreadful environmental weeds, and much depends on where they are grown. Some of the most invasive escaped years ago from domestic gardens. As well as garden weeds, there are also agricultural or environmental weeds. Trying to get rid of them is an unending and often costly struggle for all of us. Madeira vine is on the hit list.

Some definitions of weeds
There are many definitions of a “weed’ it can depend on who you are. Some definitions follow:
“A weed is a plant whose virtues have not yet been discovered”. American Diary of Organic Gardening
“A weed is a plant growing in the wrong place”. anon
“A wild herb growing where it is not wanted”. Concise Oxford Dictionary
“Any useless or troublesome plant”. The Weeds of NSW
“A weed is no more than a flower in disguise”. James Lowell
“Any plant that will survive at least one week without being watered, fertilised, pruned, sprayed, staked, mulched, misted, dusted or wrapped in burlap, paper or plastic”. Gardener’s dictionary

Camphor Laurel	Coral Tree	Giant Devil's Fig	Kudzu	Lantana	Madeira Vine	Privet	Other weeds

The problem with Weeds...
Weeds are usually not native to the area, are invasive, and have an environmental, economic and /or social impact. Weeds are estimated to cost Australia over $4 billion in lost agricultural productivity/year (Sindel 2000). Weeds threaten a number of native animals, plant species and ecological communities with extinction. Weeds can increase soil erosion, adversely affect water quality, human and animal health, and dramatically increase maintenance costs of forestry, roadside, rail, transmission line and other infrastructure.

Some weeds reduce aesthetic values and tourism opportunities in the region. The warm moist climate, relatively fertile soils and high number of visitors to the region make it ideal for the establishment and growth of weeds.

Agricultural weeds. Noxious weed legislation was originally established to protect agriculture. Most noxious weeds are therefore weeds of agriculture. Their impact apart form spread and dominance may include animal poisoning, unpalatability to stock and degradation of the resource such as burrs in sheep’s wool. In recent years environmental weeds and plants that affect human health have also been declared as noxious weeds.

Environmental weeds are generally regarded as weeds that impact on the natural environment. They often reduce plant establishment and growth, food and shelter needs of native animals and restrict the movement of both plant and animal species. They may also impact on human health, access, recreation activities, physical infrastructure and aesthetic values.

Aquatic weeds such as alligator weed, cabomba, water lettuce, salvinia, parrots feather, glush weed and water hyacinth have tremendous impacts on natural ecosystems and the industries they support. When infestation choke waterways they impact on aquatic and terrestrial animals and plants, agriculture (especially seafood), recreational pursuits such as swimming and boating, water based tourism and social life through reduced aesthetic qualities, odours and restricted movement.

Submerged aquatic plants are particularly threatening due to their ease and rate of spread, impacts and general lack of suitable control techniques. Biological control agents have proven successful at controlling some aquatic weeds.

They are still coming
Potentially threatening weeds are still being introduced to the region. Many weeds do not show weedy characteristics for a number of years. If identified as a major weed in similar locations elsewhere (such as south east Queensland), these sleeper weeds are now being targeted for immediate control. Weeds often :

• favour soil and/or vegetation disturbance
• grow in a range of environments
  
• produce many fruits. Red or black fleshy fruits especially favoured by birds
• seeds can remain viable in the soil for several years
• seeds germinate readily then grow rapidly
• flower soon after germinating
• able to grow from broken roots or above-ground cuttings
• have root-like underground (rhizomes), and
• out compete many desirable plants.

Plants may not show weedy characteristics for several years after being introduced to an area as they adapt to an area’s climate and soils dispersal mechanisms. Human activity contributes to the dispersal of approximately 90% or noxious weeds (Panetta and Scanlan 1995). Most have been introduced intentionally – as ornamental, crop or pasture species or for shade or erosion control. As weeds usually originate from other areas, they often have few natural predators to control them.

Management of weeds
Weed management requires strong community involvement and support for the following reasons:

• weeds affect everyone,
• land occupiers/owners are responsible for control of noxious weeds on their own property and they know their land the best,
• early intervention is important for the control of new outbreaks,
• many important weeds are not declared noxious and hence are not required to be controlled through legislation,
• community awareness reduces deliberate cultivation of weeds such as ornamentals,
• community members can provide important information for weed control.

For more information, download our Wilsons Creek / Huonbrook Weed Management Strategy in pdf format.

For more information
For an overall picture of how destructive some plants can be, there is a good book you can purchase called Feral Future by Tim Low and published by Penguin. It is hard to beat.

How to use this section of the website
You can find general information on weed eradication techniques as well as detailed information on the individual weed species.