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 negatively 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.

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:

  1. Do not disturb – there is a high risk of spread
  2. Contact Mornington Peninsula Shire on 1300 850 60 for advice regarding identification, its management and how to reduce its spread.
  3. 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. 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 undertaking control. 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

 File:CSIRO ScienceImage 1710 Boneseed Weed in the You Yangs Victoria.jpg - Wikimedia Commons

A Weed of National Significance, Boneseed, originally from South Africa, is a small evergreen shrub with yellow flowers, and an aggressive invader of native bushland. Boneseed grows under a wide range of climatic conditions but prefers sandy or medium-textured soils and disturbed situations, particularly near the sea because it tolerates salty conditions. Each plant produces large quantities of seed (up to 50,000 per mature healthy plants) that is readily dispersed long distances by native and feral animals. The smooth round seeds also disperse from the parent plant by rolling down slopes, and the hard seed coat allows seeds to remain viable when transported via either fresh or salt water. It has also been spread by the dumping of garden waste and by transportation of its seeds on machinery. Boneseed does not reproduce vegetatively (such as by suckers and cuttings).

Identification

Boneseed is an erect evergreen shrub, perennial being relatively short-lived (10-20 years), which grows up to 2-3 m high. It has woody branched stems. Leaves are 20–70 mm long, and 10–35 mm wide, shaped elliptic (broadest in the middle and equally narrow at both ends), with irregularly serrated edges. Leaves are fresh green, thick and soft-leathery, with a obvious mid-vein. New growth is typically covered by white downy cotton-like material (hairs). Boneseed has a shallow root system. Flower heads are in groups of 3-12, yellow with 5-8 petals and up to 3 cm in diameter. Peak flowering occurs from August to October. Young fruit is round, green and fleshy and turn black when mature.

Treatment

Because of the large and persistent seed-banks in the soil, long-term control will mean that areas have to be treated repeatedly for several years. Prevention of infestation in the first instance is clearly a priority. The shallow root system with no large taproot, means that seedlings and young plants can be pulled out by hand. Larger plant may be able to be hand pulled in damp moist soil or in sandy soil. This is not possible in heavier drier soils and the use of hand tools is required to leaver plants out of the ground (e.g. the tree popper). Registered herbicides can be used to control bone seed with the cut-and-paint method where herbicide is applied to the stump of a felled plant.

7. Bridal Creeper
     Aspagaragus asparagoides

Originally from Africa, Bridal Creeper, a Weed of National Significance, is a long lived highly invasive scrambling vine that is also an environmental weed, destroying large areas of native vegetation in southern Australia. It is easily spread by birds who eat the fruits dispersing viable seeds in dropping up to several kilometres away from the parent plant. It forms dense impenetrable thickets and smothers other plants, producing a profusion of below ground rhizomes and tubers which suppresses other ground flora and reduces available soil moisture and nutrients, excluding desirable species, also impacting native animals.

Identification

Bridal Creeper is a climbing soft herb or vine to 3 m, arising from a rhizome attached to tuberous roots. The above ground portion can die back annually or when conditions are unfavourable. The “leaves”, (called cladodes are not true leaves but flattened stems that look and function like leaves). Cladodes arise from the base of the true leaves, which are reduced to scales. The cladodes are stalkless, dull to glossy green, 10-70 mm long, 4-30 mm wide and have delicate parallel venation with no apparent midrib. The root system forms dense underground clumps of underground mats. The below ground mats are rhizomes attached to fleshy tubers. The clumps of underground stems are capable of vegetative reproduction, producing new stems and plants if the stems and leaves are removed or die back in unfavourable conditions, like a bulb does. The root system can be dense extending 100-200 mm below ground, up to 200-400 mm long or more, initially vertical but then horizontal somewhat below along the soil surface forming dense impenetrable mats. The individual pale flowers occur in the leaf axils, are scented and small to 8–9 mm wide. The fruit is a bright round red fleshy berry. Each fruit produces shiny black seeds.

Treatment

The extensive root system and prolific seed production makes control difficult. Removal requires a very long-term commitment over decades, with repeated control action and monitoring requiring an integrated management strategy. Integrated control methods combining techniques, with long term follow-up is advised for success. All control programs should aim to reduce the number of seed produced, with prevention the most cost-effective form of weed control. When controlling Bridal Creeper the underground rhizomes need to be fully removed or comprehensively killed as re-growth can occur. Hand pulling is suitable for small plants and infestations, however if the plant breaks leaving any or all the rhizome, plants will regrow. Large plants with extensive root systems and underground rhizomes can also survive herbicide application. Biological control is regarded as a preferred initial management option for larger infestations of Bridal Creeper. Three biological agents have been release for the treatment of Bridal Creeper, the undescribed Erythroneurini leafhopper, a rust fungus Puccinia myrsiphylli, and a leaf beetle (Crioceris sp.).

8. English Ivy
     Hedera helix

English Ivy (Hedera helix) is a spreading and climbing vine. It is a very hardy plant growing in a wide variety of habitats and soils, readily rooting along the stem and growing from discarded cuttings. The berries are attractive to birds, its main dispersal method. It is an aggressive invader, capable of toppling large trees. English Ivy is an aggressive invader that threatens all vegetation levels of forested and open areas, growing along the ground as well as into the forest canopy. It excludes the native vegetation and results in a loss of biodiversity. The dense growth and abundant leaves, which spring from the stems like small umbrellas, form a thick canopy just above the ground and prevent sunlight from reaching other plants. Vines climbing up tree trunks spread, surround and cover branches and twigs, preventing most of the sunlight from reaching the leaves of the host tree thus reducing photosynthesis. Loss of host tree vigour, evident within a few years, is followed by death a few years later. The added weight of vines makes infested trees susceptible to blow-over during storms.

Identification

English Ivy has dark green waxy leaves which are arranged alternately along the stem. English (and Irish Ivy) have many recognised cultivars with 100s if not 1000s of leaf leaf forms different from the wild species size and shape. The juvenile leaves that are the most common leaf shape are 3-lobed or occasionally 5-lobed, which climbs by roots produced from the stem. After reaching a certain size, and usually when it grows tall enough to get into the sun, the plant can assume its mature form, with un-lobed, oval leaves. Mature leaf branches and stems can now only produce mature leaves, and cuttings from the mature form remain mature. The adult leaves are only produced when the plant flowers on the upper parts of the plants (rarely when growing along the ground), and are not lobed. Intermediate mature leaves can show lobbing at the base of the branch, but not at the top of the branches with flowers. Umbrella-like clusters of small, greenish-white flowers appear in autumn if sufficient sunlight is available. The berry-like fruits mature in spring and are purplish to black with a fleshy outer covering enclosing one to a few hard, stone-like seeds.

Treatment

Best practice management includes physical control – English Ivy vines growing as groundcover can be pulled up by hand. Make sure to remove all stem parts from the ground as they will take root and regrow. If removal from site is difficult ensure vines are placed off the ground to dry out and decompose. Alternatively, seal in strong bags and dispose as rubbish. Mulching may be an effective choice for smaller infestations when herbicides are not appropriate. Cover the entire infestation with several inches of mulch, which may include wood chips, or similar (weed free) degradable plant material. Covering the area with cardboard may improve the effectiveness and longevity of this method. The mulch should stay in place for at least two growing seasons and may need to be augmented several times. Vines climbing up into the tree canopy are more difficult to manage and should be cut to a comfortable height to kill upper portions and relieve the tree canopy.

Because it is an evergreen vine and remains active during the winter, herbicide applications can be made at any time of year as long as temperatures are above 15 degrees Celsius for a few days. Use a registered herbicide using the cut and scrape method. Repeat herbicidal treatments are usually necessary and follow-up monitoring should be conducted to evaluate the success of treatments.

9. Myrtle-leaf Milkwort
     Polygala myrtifolia

Originally from South Africa, Myrtle-leaf Milkwort is a highly invasive evergreen shrub to 3 metres tall that grows in southern Australia in sandy to calcareous soils, particularly along coastal areas and near-coastal shrub-lands. It is capable of invading intact vegetation forming dense stands and prevents or limits the establishment of other species, eventfully completely dominating the shrub layer. Following an assessment process, Myrtle-leaf Milkwort was not included as a Weed of National Significance, however, it remains a weed of potential national significance and is a serious invader of Mornington Peninsula coastlines. Myrtle-leaf Milkwort is spread by seeds by animals through entanglement in fur or feathers. and potentially dispersed via in dumped garden waste or movement of contaminated soil.

Identification

Myrtle-leaf Milkwort is a bushy to sparse shrub growing to about 3m high. Leaves are crowded close together along the stem and are arranged alternately. Leaves are oval or broadly elliptic with smooth leaf edges and leaf tip. Leaves are 15-40 mm long and 5-20 mm wide. The flowers occur in clusters mostly 1.5 to 4 cm long at the tips of younger stems and are white, pink and mauve. Individual flowers are pea-like with spreading ‘wings’ that are 12 to18 mm long, 7 to 13 mm wide, purple or mauve on their inner surface and green outside. The central ‘keel’ of the flower is slightly shorter than the wings, white or pale mauve with a maroon blotch and a tuft of pale hair-like outgrowths at the tip. The fruit is a capsule, flattened and more or circular with a notch at the tip, 8 to10 mm long and wide, green at first but when ripe turning a dry brown-straw colour. Each fruit produces two hairy black seeds about 4.5 mm long. Seeds seeds remain viable in the soil for 2 to 3 years but are reported to be long lived (up to 10 years or more).

Treatment
Any treatment of Myrtle-leaf Milkwort should occur over several years with follow up required to remove the seedling that normally germinate on mass when parent plants are removed. Young plants may be removed by pulling or shallow digging or treated chemically using the cut and paint technique, but these are unlikely to be practicable in heavy infestations. For heavy infestations, consider burning or chemical control by an experienced contractor.

10. Radiata Pine / Monterey Pine
       Pinus radiata

Radiata Pine is a tall 25m aromatic evergreen tree with needles (leaves) in groups of three, and whorled branches and woody cones. It is used for softwood plantations worldwide, however invades a wide range of Australian ecosystems. Seeds are equipped with winglike structures and can travel up to a km on the wind, as well as being dispersed by native wildlife such as Yellow Tailed Black Cockatoos. Radiata Pine can have a dramatic effect on the environment. The thick pine leaf litter can reduce the fertility and change nutrient cycling in soils as well as changing the water cycle. This leaf litter will also create a thick layer that prevent seedling establishment especially of native species reducing plant biodiversity in the area.

Identification

Radiata Pine is a tall, aromatic, evergreen tree with a straight trunk and many whorled branches. The bark is rough due to deep fissures and vertical ridges on older trees, bark dark brown or grey, or black brown. Slender, grass-green leaves appear in groups of three, 8–15 cm long. This plant has no flowers but produces male and female cones on the same tree which occur singularly, paired or in whorls around the branches. The cylindrical soft male cones are much smaller than female cones, clustered at the branch tips and only present for a limited time, falling from the tree after large amounts of pollen is shed into the air and dispersed via wind. Female cones are solitary or in clusters, shortly stalked and pendulous, grayish-brown that weathers to a dull grey.  Cones are asymmetrically ovoid,  7 – 15 cm long and 6 to 12 cm wide, usually persistent with cones able to stay on the tree up to five years while still holding viable seeds. The seeds have well-developed wings which help with wind dispersal.

Treatment

Radiata Pine control methods are similar to other woody weed controls. Control work should be planned to minimise disturbance to existing native vegetation. Controlled sites need to be monitored and follow-up treatment applied to re-sprouting stumps and seedlings. Saplings should be controlled before reaching sexual maturity at four years of age. Seedlings can be hand pulled or dug out as long as the main root is removed. More mature infestations can be treated by cutting and painting using a registered herbicide, or by drill/frill and frilling, leaving the plant to die and rot insitu.  Trees can also be cut down or ringbarked without the need for herbicide use. As these plants can provide much needed food for native Cockatoo species, staged removal is recommended while waiting for replacement indigenous species such as Sheoaks reach maturity.

For extensive weed profiles on these and more weeds go to: https://weeds.org.au/