Priority Weeds

Weeds are a major threat to remnant vegetation and the fauna that rely on locally native plants for survival. Weed invasion is responsible for the loss of many species of plants and animals from areas across Australia, including the Mornington Peninsula. Weeds also impact on waterways, stock, crops, tourism.

Weeds can be classified as Environmental, Noxious, a Weed of National Significance, and sometimes can be all three. Below is a list of the Mornington Peninsula Landcare Networks Top 12 weeds, however there are many that could have been placed on this list. For a more comprehensive list, please see the Mornington Peninsula Shire’s GUIDE TO NOXIOUS & ENVIRONMENTAL WEEDS OF THE MORNINGTON PENINSULA

Landcare’s Top 10 Environmental Weeds

1. South African Weed Orchid
Disa bracteata

An emerging threat to the Mornington Peninsula’s native wildflower populations, this highly invasive environmental weed produces millions of dust-like seeds allowing it to spread easily and form dense colonies. If we allow this plant to invade unchecked the consequences could be devastating.

South African Weed Orchid is the only invasive non-native orchid in Victoria. First found in the 1940s, South African Orchid has established populations across the state. Most plants are found in
moderately disturbed areas. However, it does invade bushland, where it can compete with and exclude smaller native plants such as lilies, grasses and orchids.

Identification

South African Onion Weed is erect, fleshy and can reach up to 50cm high. The green leaves form a rosette and have purple undersides. It grows above-ground annually from tubers. Each plant has up to 60 tiny flowers along a dense spike. It flowers mainly during Sep–Dec. The small flowers have a red-brown hood and and a yellow labellum (larger bottom petal) that protrudes forward like a tongue. The black, minute and dust-like seeds are contained within the fruit.

Lookalikes

South African Weed Orchid may be confused with similar native species, Microtis spp. and Leek-orchids (spp.), however our native orchids can be distinguished as they have only a single leaf emerging at the base of the stem.

Treatment

If you suspect that you have found a South African Weed Orchid infestation:

Do not disturb – there is a high risk of spread
Contact Mornington Peninsula Shire on 1300 850 60 for advice regarding identification, its management and how to reduce its spread.
Connect with your neighbours and local Landcare Groups to undertake control, share what management methods have been successful, and work together to manage the spread collaboratively.

For small infestations, manually dig up and remove all parts of the plant, including the tuber, leaves and flowers before seed set. Bag all material securely to prevent the fine dust-like seed from spreading and dispose in general waste (not green waste). Large infestations need to be chemically controlled.

2. Karamu
Coprosma robusta

Karamu is a serious environmental woody weed on the Mornington Peninsula. It spreads mainly by bird-dispersed seed and forms dense impenetrable thickets which impede the growth of native plants and prevent their regeneration. Worryingly, it can also hybridise with our native coprosma species.

Identification

An evergreen tree or shrub growing to up to 6 meters tall. It has thick glossy green leaves that are between 5-6 cm in length and oppositely or symmetrically arranged. The leaves are oval-shaped with slightly wavy margins. Leaves are paler underneath with a distinct midrib, however the midrib is not raised on the upper surface. The plant produces small, white, waxy, inconspicuous flowers followed by bright orange-red berries.

Lookalikes

Karamu has two native plants that it can be confused for. Rough Coprosma which grows locally in isolated patches of a few plants, not dense thickets. It has thicker, darker, leaves that feel like sandpaper on the top. They are broader at the base and have long pointed tips and red fruits. The second plant is Muttonwood, which grows in dense groves and has more elongated leathery leaves with wavy margins and a pointed tip. Its pale flowers are followed by clusters of purple fruits.

Treatment

Control of Karamu requires an integrated program utilising manual control and herbicide application, and a strategy that preferentially targets fruit-bearing plants.

3. Sweet Pittosporum
Pittosporum undulatum

Sweet Pittosporum is an Australian native that has become a serious environmental weed on the Mornington Peninsula, growing outside its limited natural range. It effectively shades out indigenous vegetation beneath a dense canopy, changes soil nutrients and contributes to changes in native lizard and bird populations. A fire-sensitive species, Sweet Pittosporum often replaces fire-adapted species, increasing the fuel load and bush fire risk.

Sweet Pittosporum reproduces by seeds and suckers. Spread has been encouraged by gardeners who praise its hardiness and sweet perfume. Seeds are dispersed by fruit eating birds and other animals including foxes and possums. It also spreads in dumped garden waste and contaminated soil with seeds sticking to animals and footwear.

Identification

A tall evergreen shrub or small tree that can attain heights of 25 m and a spread of up to about 12 m wide. Its foliage is very dense creating areas of deep shade beneath its canopy. Leaves are alternately arranged, or clustered at the end of branches with a leaf stalk 12–15 mm long. Leaves are ovate, oval or narrowly obovate , usually 6–17 cm long, 1.5–4 cm wide, shiny and dark green above, paler beneath, and have entire (lacking teeth) undulate margins (wavy edges) or occasionally flat (edges not wavy). The leaf tip is sharply to gradually pointed with new growth in winter and spring a lighter green.

It forms creamy white sweet-scented flowers in early spring. Flowers are either male or female with plants either producing exclusively male or female flowers. Flowers are found in clusters of 4–5 at the end of stems. Male flowers have petals 1–2 cm long, narrower than in female flowers, with anthers exerted from throat of flower. Female flowers are generally 12–14 mm long with infertile male organs (staminodes) and a plump stigma. The fruit appear in Autum to Winter and are hard and green capsules, turning yellow then vivid orange, 8–13 mm long and 10–15 mm wide. When ripe they split open revealing 20–30 brownish-red sticky orange seeds.

Treatment

As this is a Victorian native, removal may require a permit. Depending on its stage of growth, Pittosporum can be removed by grubbing out by hand (seedling), or using the cut and paint method (intermediate) or drill and fill (mature shrub/tree). Sweet Pittosporum is favoured by Powerful Owls, so please take this into consideration when selecting a control method. For large infestations, target the female (reproductive) plants first.

4. Blackberry
Rubus fruticosus aggregate

Blackberry is a priority Noxious weed, a Weed of National Significance (WONS) and Regionally Controlled under the CALP Act 1994, so landholders are legally required to take reasonable steps to control it in Victoria. Blackberry forms impenetrable prickly thickets and mounds that fill gullies and hillsides, smother indigenous shrub and ground vegetation layers, and prevents germination of trees and shrubs preventing succession. European Blackberries can infest large areas quickly as they are vigorous growing plants by seed or vegetative growth. Thickets can pose a fire hazard because of the dry material contained within them. Larger native wildlife may become trapped in the prickly thickets while smaller animals, including feral rabbits and foxes use these thickets as shelter. It also provides food for introduced species such as starlings, blackbirds, and foxes who subsequently spread Blackberry into new new areas.

Identification

Blackberries grow as dense, arching, and sprawling thorny shrubs (brambles) with woody stems, or “canes,” that can reach several meters in length and often root at the tips where they touch the ground, forming thickets. The canes are typically green when young, turning reddish or purple with age, and can be round or angled. They feature prominent curved or straight prickles (thorns) along the entire length. The leaves are compound, meaning each leaf is made up of smaller leaflets. They are usually arranged in groups of three or five leaflets that have jagged, serrated edges. The top surface of the leaf is dark green, and the underside is often a lighter green and can be covered with fine hairs. Flowering in late spring and summer, the plant produces clusters of flowers with five white or pink petals and many stamens. The fruit is an aggregate of many tiny, juicy segments called “drupelets”. They ripen from green to red, and finally to black when mature.

Lookalikes

The locally indigenous native raspberry Rubus parvifolius, occurs in the same habitats and is often mixed with Blackberry. It has been removed in the mistaken belief that it was a weed. Native Raspberry is a scrambling, perennial, prickly shrub that grows to 1 m long; bright green wrinkled leaves, downy-white hairy underneath, growing in groups of 3-5 leaflets with the terminal leaflet usually the largest. Flowering in late summer, it has pink or red flowers with 5 petals to 10mm and an edible red raspberry-like fruit. Native raspberry can be differentiated from introduced blackberry by its strong pink or red flowers, red raspberry like fruit, or in their absence, the smaller, lighter ovate leaflets and hairy stems. It also has two sets of paired leaves that are well spaced as opposed to Blackberry that often has one set or two not spaced far apart.

Treatment

Prescribed methods of control include grubbing out by hand or application of a registered herbicide using the stem scrape, cut and paint or spot spraying conducted in the active growing phase (Spring/Summer). Spraying is only suitable where there is no risk of off-target damage to indigenous plants. The cut and paint technique offers a more sensitive chemical control option and is suitable in bushland settings. There is also a biocontrol agent available for Blackberry, an introduced fungus called Blackberry Rust that thrives in wet summers and can reduce the vigour of plants.

While a harbour for pest animals, it should be noted that blackberry can also provide shelter for small native birds and mammals from predators such as foxes and cats. Where there is little alternate habitat (mid-storey prickly shrubs) nearby, treat larger infestations in small patches while establishing native prickly plants as replacement habitat.

More information and support visit the Victorian Blackberry Taskforce website.

5. Gorse
Ulex europeaus

Gorse is a spiny, evergreen shrub in the pea family (Fabaceae) that is a Weed of National Significance (WoNS) in Australia due to its aggressive invasiveness and substantial economic, environmental, and social impacts. In Victoria, it is legally classified under the Catchment and Land Protection Act 1994 as Noxious and “regionally controlled” across the Mornington Peninsula, meaning landowners must take action to prevent its growth and spread.

It forms dense, impenetrable thickets, displacing native species and increasing bushfire risk through its accumulation of flammable biomass and oils. Its dominance can lower pasture productivity, restrict access, degrade riparian zones, and even alter soil chemistry over time. Mature plants produce thousands to millions of seeds annually, which can remain viable in the soil for 25–50 years (sometimes up to 80 years). Pods release seeds explosively in hot, dry conditions, dispersing up to 5 m. Seeds also spread via water, soil movement, livestock, birds, ants, and machinery. Germination is triggered by fire, soil disturbance, or passage through animal digestive systems.

Identification

Gorse in an evergreen shrub that grows up to 4 m tall and 3 m wide with rigid, spiny branches. Its leaves are narrow, waxy-coated, 6–30 mm long with sharp tips. Seedlings have soft trifoliate leaves. Bright yellow coconut-scented pea-like flowers, 15–25 mm long bloom in spring and autumn. Hairy, oblong pods (10–20 mm) containing 2–6 hard triangular seeds form after flowering.

Treatment

Plan strategically & establish clear priorities, preventing new infestations via good hygiene practices and early detection and control. Employ manual and/or chemical control tailored to infestation size and setting. Cut and paint technique is suitable for small manageable infestations. You may also use biological agents such as the Gorse Spider Mite or Gorse Weavil, or the use of controlled burns when appropriate. Actively monitor for seedling emergence, remembering that persistence is key as gorse have very long-lived seed. Burning can help to speed up germination of gorse, eventually exhausting the soil seed quicker, however this will only work if followed up by immediate control measures. If you coordinate with neighbouring landholders, you can help to prevent re-invasion. Adopting an integrated strategy ensures effective, long-term control of gorse in bushland environments. Replace them with indigenous shrubs

More information and support visit the Victorian Gorse Taskforce website.

6. Boneseed
Crysanthemoides monilifera