One of the worst weeds on the foreshore is Bridal Creeper, (Myrsiphyllum asparagoides). It is a creeper that spreads via seed eating birds and animals, and also via many underground corms. Roots grow from wherever the vine touches the ground. If left to grow freely it can completely smother the indigenous vegetation. Fortunately biological controls have been found to succeed in controlling the plant with the use of a rust fungus and a mite, which together have suppressed the spread of this extremely invasive climber. Originating in South Africa, it was a popular hanging basket plant sold by many nurseries in the past!
Another South African plant, which grows to a 5 meter shrub, is Boxthorn (Lycium ferocissum). Aptly named, it has 15cm long spines on its branches making it impossible to remove by human hand. The council has resorted to using big machinery to extract them, trying not to leave the large thorns in the dunes. Again it is spread by birds and animals eating the bright red fruit. It replaces the natural shrubs of the foreshore such as coastal ti tree, coastal beardheath and boobialla, the major shrubs of the Coastal Dune Scrub.
The New Zealand Mirror Bush (Coprosma repens), displaces indigenous shrubs too. This exotic weed grows rapidly on the coast, spreading in exactly the same manner with its red berries. Removal is easier (no thorns) by sawing and applying herbicide to the stumps. Disturbance and clearing of vegetation creates the ideal situation for the introduction of more weeds, such as veldt grasses or deadly nightshade, so it is paramount to manage an area properly and clear at a time when replacement is going to be successful, by planting or direct seeding, timing and season being considered.
One of the most natural looking grass weeds of the foredune is Marram Grass (Ammophilla arenaria), a European tussock introduced for dune stabilisation. It can take over the role of the indigenous hairy spinifex, but if examined closely the dune form is quite different. The tall tussock forms a clump creating steep sided dunes, whereas the horizontal runners of the Spinifex sericeus encourage wide gently sloping dunes less prone to erosion. To remove the weed when it is the only plant binding the sand would be deleterious, but gradual replacement with the well adapted Spinifex would improve the quality and stability of the foredune. Where healthy areas of Spinifex exist any marram grass encroaching should be removed, by cutting and painting with herbicide.
Over the years, the bright yellow flowers of the Gazania species that has colonised the coastal areas of Frankston have slowly disappeared thankfully, as this south African plant exudes a chemical inhibiter around it, discouraging growth of the natural vegetation, ensuring its own survival and spread along the length of the foreshore. This is an escaped garden plant, like so many of our weeds. When residences are close to the foreshore reserve, the likelihood of this happening with other garden plants is high, particularly if garden rubbish is dumped on the dunes.
Polygala myrtifolia, a south African shrub, is one that is often planted for its bright purple pea flowers and spreads rapidly on coastal areas.
Other weeds found on Frankston Foreshore:
- Hare’s Tail (Lagurus ovatus)
- Cape Ivy (Delairea odorata)
- European Sea Rocket
- Dolechos (Dipogon lignosis)
- Cape Broom (Genista monspessulana)
- Angled Onion
- Buffalo Grass
- Sweet Hakea (Hakea suaveolens)
- Sea wheat grass (Thinopyrum junceum)
The most difficult two weeds to identify on the foreshore are Sallow Wattle (Acacia longifolia) and the South African species of Carpobrotus, as they are visually fairly close to their indigenous counterparts, Coastal wattle (Acacia sophorae) and Pigface (Carpobrotus rossi).