Know Your Weeds

What is a weed?

The definition of a weed: a plant growing where it is not wanted where it also takes over and displaces native species.

Most of the plants that are now weeds in Western Australia were introduced deliberately, as garden ornamentals, pastures, or food crops.

Some introduced plants have been promoted for use in gardens because of their low maintenance and water-wise properties. However, without any of the diseases or predators (such as insects that eat their seeds) that keep them in control in their natural environment, these plants have thrived and spread into areas where they are not wanted such as bushland and neighbours’ properties.

Many of the weeds in Western Australia come from Europe, South Africa, the Americas and eastern Australia.

Why Are Weeds a Problem ?

Weeds compete with other plants for space, water and nutrients. In bushland, weeds can out-compete native understorey, create dense shade—which prevents germination and establishment of native species—and increase fuel loads and fire hazard. The subsequent loss of habitat and food sources impacts on native fauna.

In a suburban environment, native vegetation on road verges and areas of remnant vegetation are particularly important. They provide food and refuge for native fauna, help to preserve biodiversity, and create beautiful areas to enjoy.

How Do Weeds Spread?

Weeds may be spread by:

  • the accidental movement of seed attached to shoes, clothing or vehicles;
  • the inappropriate disposal of garden waste; and
  • the movement of seed by wind, water and animals. Particularly invasive weeds may have characteristics that make them so ‘successful’, such as:
  • the production of large quantities of seed that remain viable in the soil for several years;
  • effective seed dispersal mechanisms;
  • the ability to spread by vegetative means, such as rhizomes, bulbs, and corms;
  • rapid establishment and growth; and
  • the ability to invade disturbed areas, such as road verges.

How You Can Prevent Your Garden From Contributing to the Weed Problem?

Weeds may be spread by:

  • Remove existing invasive plants in your garden and replace them with local natives (as outlined on this page).;
  • When buying new plants, choose plants that are local to your area. Sometimes plants from eastern Australia are labelled as ‘native’ but are not native to WA and may be invasive (such as weedy wattles).
  • Dispose of garden waste responsibly: don’t dump it over the back fence, on roadsides or in bushland; and cover your trailer when taking garden waste to the tip to stop weeds and cuttings falling off and invading roadside bushland. Alternatively, compost garden waste in your own backyard.

No Weeds – Plant Me Instead!

Alternate plants to plant:

  • Myrtle-leafed MilkwortWEED: Myrtle-leafed Milkwort (Polygala myrtifolia)
    Originally from South America, Polygala is a bushy shrub to 2m high with oval leaves and mauve-purple pea shaped flowers. It flowers throughout the year, most predominantly in Spring. Seeds are spread by water, birds, ants, dumped garden waste, and the movement of soil. Seeds can persist in the soil for at least years. To remove, hand pull seedlings and fell mature plants. Follow up by removing germinated seedlings.

    Alternative to options to plant instead of Myrtle-leafed Milkwort

    Graceful Honeymyrtle (Melaleuca radula)
    A medium shrub to 2.4m, pink-purple flowers from July to November. Hardy and attractive to birds.
    Graceful Honeymyrtle
    Plumed Featherflower (Verticordia plumosa)
    A low, rounded shrub to 1.5m high, pink-purple flowers from July to February.
    Plumed Featherflower

     

  • WEED: Spanish Lavender (Lavandula stoechas) or French Lavender (Lavandula dentata) 
    Lavender is native to the Mediterranean Region and grows to 1m. Large plants produce prolific quantities of seed, which are long-lived and are spread by wind, water, birds, ants, dumped garden waste, and the movement of soil. Hand pull or dig out small plants ensuring you remove all root material, as it can re-sprout. Remove spent flower heads immediately after flowering to prevent seed spread.

    Spanish LavenderFrench Lavender

    Alternative to options to plant instead of Spanish Lavender (Lavandula stoechas) or French Lavender (Lavandula dentata)

    Coral Vine (Kennedia Coccinea)
    Twining or trailing shrub. Coral pink pea flowers from August to November.
    Coral Vine
    Melaleuca seriata (no common name)
    A low shrub to 1m high. Pink-purple-red flowers from August to December.
    Melaleuca seriata

     

  • Veld DaisyWEED: Veld Daisy (Dimorphotheca ecklonis)
    Veld Daisy (or Cape Daisy) is native to South Africa and grows to 0.5m high. Leaves have strong smell when crushed and seeds are spread by wind, water, dumped garden waste, and the movement of soil. Hand pull or dig out small plants ensuring you remove all root material, as it can re-sprout.

    Alternative to options to plant instead of Veld Daisy

    Autumn Scrub Daisy (Olearia paucidentata)
    Erect shrub to 0.2-1.2m high. Purple-blue/white flowers from January to December. Not available at Plants to Residents but is available at good native nurseries.
    Autumn Scrub Daisy
    Broad-leaved Fanflower (Scaevola platyphylla)
    Erect spreading shrub 0.3-1.3m high. Purpleblue flowers from August to December. Prefers laterite soils in the hills, breakaways and road verges.
    Broad-leaved Fanflower

     

  • Flinders Range WattleWEED: Flinders Range Wattle (Acacia iteaphylla)
    This wattle is endemic to the Flinders Ranges of South Australia and has become invasive outside of this region. It is a dense shrub to 4m. Seeds are spread by water, birds, ants, dumped garden waste, and the movement of soil, and are long lived (greater than 5 years). To remove, hand-pull seedlings and fell mature plants.

    Alternative to options to plant instead of Flinders Range Wattle

    Toothed Wattle (Acacia dentifera)
    A medium shrub to 3m high. Yellow flowers from August to November.
    Toothed Wattle
    Glowing Wattle (Acacia celastrifolia)
    A dense tall shrub or small tree to 4m high. Yellow flowers from April to August.
    Glowing Wattle

     

  • Mile-a-Minute Blue Morning GloryWEED: Mile-a-Minute ( Ipomoea cairica) & Blue Morning Glory (Ipomoea indica)
    Both commonly called Morning Glory, these vines produce purple, blue and pink flowers. They can invade gutters and eaves, smother other plants and jump the fence into neighbouring properties. They spread by roots and shoots, and the production of large quantities of seed that are dispersed by wind and water. Small infestations can be manually removed. Vines can be severed at the base and left to dry out.

    Alternative to options to plant instead of Mile-a-Minute & Blue Morning Glory

    Native Wisteria (Hardenbergia comptoniana)
    A twining shrub or climber. Climbs to 4m. Purple or white flowers from July to October.
    Native Wisteria

     

Other Garden Escapees Not Listed Here:

  • Black-eyed Susan – Thunbergia alata
  • Century Plant – Centaurium sp.
  • Freesia – Freesia alba x leichtlinii
  • Gazania – Gazania sp.
  • Lantana – Lantana camara
  • Olive – Olea europaea
  • Pink Gladiola – Gladiolus caryophyllaceus
  • Prickly Pear – Opuntia sp.
© City of Kalamunda 2019