Blackberry - all you need to know!
Published on 01 February 2023
Blackberry, or European Blackberry (Rubus fruticosus aggregate) is one of Australia’s most widespread weeds, a serious issue across much of Victoria, and a significant threat to our biodiversity.
An aggregate is a grouping of closely-related species that are treated like a single species for practical purposes. The Rubus fruticosus aggregate contains at least 9 distinct species in Victoria, along with hybrids.
About the Blackberry
What does it look like?
Blackberry is a prickly, scrambling plant, appearing as a semi-prostrate to almost-erect shrub. The plant’s stems, also known as canes, arch and trail and can form thickets 2-3m high and up to 7m long.
The leaves of blackberry plants are comprised of three or five leaflets (with all the leaflets about the same size and shape). These leaflets are usually dark green on the top side and lighter green underneath, with small teeth around the edges.
It produces pink or white flowers, 2-3cm in diameter, and fruit in the form of a berry. These berries, which develop from late December until April, range in colour from green to red to black, depending on their ripeness. They are 1-3cm in diameter.
Does it look like any native plants?
In Maroondah, Blackberry may be mistaken for Native Raspberry (Rubus parvifolius), which has a similar scrambling habit. However, the leaflets of the Native Raspberry are smaller, and the ripe fruit is red. It also never grows into a dense thicket, the leaves are trifoliate, and the central leaflet is larger than the other two leaves.
How does it spread?
Blackberry can infest large areas quickly. Animals such as birds, foxes and other mammals eat the fruit and distribute the seed over wide areas. Seeds are also transported by water along creeks, drains and rivers. The plant’s canes attach to the ground and form daughter plants, further increasing the size of the plant.
Where does it grow?
This invasive weed grows throughout all the higher rainfall (over 760mm annual average) regions of Victoria, particularly in bushland, forest plantations, along streams and on grazing land.
Why is Blackberry a problem in Maroondah?
Blackberry provides food for introduced species such as starlings, blackbirds, and foxes. These animals then contribute towards spreading the weed into new areas. Feral rabbits and foxes also use Blackberry thickets as shelter.
The plant spreads easily into revegetation and remnant bush sites, filling gullies and hillsides, smothering native shrub layers and ground vegetation, and preventing germination of indigenous species. Being a robust plant, it can become established in a variety of soil conditions; creek-lines, waterways, hard-dry areas, disturbed land and waste land, and quickly establishes in areas of biological significance.
Blackberry thickets can also reduce the natural attraction of the bush as well as hindering recreational opportunities by preventing access to natural features.
Blackberry can be difficult to control as its root system can be extensive. Its method of spreading rapidly via canes creating new roots means that more resources are required to control the ever-increasing size.
Larger plants have reduced treatment success as the plant has greater ‘energy’ to withstand treatment. This can then lead to the plant having the potential to become a ‘super-plant’, producing an inherent ability to withstand further treatment. Seeds of these ‘super-plants’ share these stronger traits and continue the cycle of producing treatment-resistant plants.
Spring is when the plant will emerge, grow leaves, flower, set fruit and be spread by birds and foxes, but summer, when the plant is healthy and growing, is the most effective time to control blackberries.
There is a small window of opportunity to treat the weed during the active growth period. Following this period, the plant is dormant for the rest of the year during the cooler months and treatment will not be as effective.
Herbicides are the most reliable blackberry control method. It can sometimes be an advantage to employ a weed control contractor with the correct qualifications, equipment and experience to control blackberry. To treat the plant, spray with herbicide once the flowers have formed, before the plant produces fruit. The general aim is to limit the amount of fruit being produced. Do not consume the fruit once it has been chemically treated. Do not remove treated canes (burn off, cut or clear blackberry) for 6 months after spraying to ensure complete translocation of herbicide to the plant’s root system.
Alternative methods of control
Apart from digging out and ensuring the entire root system is removed, herbicide is the best approach.
The success of using goats depends on continual presence of the animal, especially when flowering and fruiting of the blackberry occurs. The plant will be contained, but not necessarily die. Goats may be used to eat seedlings, thus preventing them from growing.
To cut back on the use of herbicide when treating vast quantities of canes, the vegetative matter can be slashed and removed from site, and the regrowth spot-sprayed. Not only does this method reduce the amount of herbicide used, but it also reduces possible spray drift and off-target damage. The regrowth can also be cut and paint with herbicide.
Currently the only biological control agent tested and released into Australia is the leaf rust fungus (Phragmidium violaceum), which attacks only European blackberry. The rust is highly efficient at spreading by natural means and will colonise blackberry when environmental conditions are suitable.
Blackberries are a Weed of National Significance (WoNS) in Australia. The species aggregate R. fruticosus is a declared noxious weed in Victoria under the Victorian Catchment and Land Protection Act 1994. R. fruticosus is declared a regionally controlled weed in the Wimmera, Glenelg-Hopkins, North Central, Corangamite, Port Phillip and Westernport (West and East), Goulburn Broken, North East, West Gippsland and East Gippsland Catchment Management Authority (CMA) areas, and it is a Restricted weed in the Mallee CMA region. Under the legislation, landowners must take all reasonable steps to prevent the growth and spread of regionally controlled weeds. The sale, trade, transport or display of restricted weeds is prohibited throughout the State of Victoria.
Removal on private property is the responsibility of the property owner. Council can issue a Notice to Comply to private property owners for removal of blackberries.