Blackberries (Rubus spp.) weed or native?

Blackberries are delicious…but they are also one of Australia’s worst environmental woody weeds.

Blackberries were introduced in the 1840s in New South Wales, and the plants quickly spread throughout the Country via birds and other animals. In the 185os, von Mueller deliberately spread blackberry seeds into the Victorian bush so that hikers could enjoy a snack on their travels. They can tolerate a wide range of environmental conditions but are less successful in drier climates. There are approximately 250 species of Rubus worldwide, with around 25 occurring in Australia, including 8 natives. The many variants and species of European blackberry are difficult to identify to species level so are all commonly referred to Rubus fruticosus spp. aggregate. Today, they are collectively considered a ‘weed of national significance’ and are a serious threat to our native vegetation.

What is less commonly known is that Australia has a few native species of Rubus. In Victoria, the most common is Native Raspberry, Rubus parvifolius. It occurs throughout the State and often co-occurs with the introduced species. Unfortunately, the native and introduced species look superficially similar, so the native species is often misidentified as a weed and treated as such. So, I thought I’d write a post detailing the differences between these two.

In the following pairs of photos, the native species, Rubus parvifolius is always on the right. All photos were taken by myself.

Leaves

The leaves of both species are very similar, as you can see below. Both usually have five leaflets, although R. parvifolius are smaller and sometimes only has three. In R. fruticosus the leaves usually join at the same point and are therefore ‘palmate’, but since the basal leaves of R. parvifolius join lower, the whole arrangement is ‘pinnate’. Both plants have a pale or white underside of the leaf (shown below). Both also have have distinct leaf venation but this is strongest in R. parvifolius which has deep veins and an almost wrinkled or pleated appearance.

Leaf spotting characters: check if the two lowest leaflets come from the same point as the other leaves, or further down. Check the leaf surface for deep veins.

Thorns

Blackberries are very thorny. This makes them even more difficult to manage, but also makes them great refuges for small animals. Both the introduced and native species have thorns, but their shape is different. R. fruticosus thorns are directly straight (see below left) and are quite long. R. parvifolius thorns are often much smaller and curved away from the shoot tip (see below right). This is probably the most reliable spotting character but be sure to look at a few thorns on each plant as there are always one or two that don’t fit in.

Thorn spotting character: are the thorns curved or straight?

Flowers and fruits

The flower arrangement for both the introduced and native species is generally paniculate, meaning that the flowers are arranged alternately along a small set of flower stalks. This feature is relatively inconsistent though, particularly in R. fruticosus, and racemes or cymes  of flowers are common, and can be solitary in R. parvifolius. Both plants have flowers with five petals and five sepals. Petal colours are similar and can be white to pink in R fruticosus, and pink to red in R. parvifolius. Blackberries are prolific fruit producers and the very tend to go black when ripe for most species variants, whereas R. parvifolius has low fruit production and are red when ripe.

Flower spotting character: flower colour darker pink to red is more likely to be R. parvifolius.

I hope the next time you see a ‘blackberry’ bush, you take a second look to check if it is a native or introduced species.

 

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