Blackberry

The berries may be delicious but blackberry is a troublesome bramble weed throughout the region.

Credit: Weedbusters

‘Blackberry is a highly invasive and troublesome weed that receives a mixed reception: who passes up handful of ripe blackberries when passing a good patch in summer?  And yet, so much of our work involves controlling this plant where it is taking over valuable habitat, smothering other plants and reducing the establishment of natives. It is often an unwelcome intruder over the garden fence too.’

Katrina Merrifield, Biosecurity Advisor at GWRC

Why is it bad?

Blackberry invades natural ecosystems, smothering native vegetation. It is also a problem in pasture, plantation forests and peoples’ backyards.

It forms dense, long-lived clumps, scrambles over the ground and low plants, has an extensive root (rhizome) system capable of producing new plants. Blackberry thrives in open areas and tolerates most soil types, drought and flood.

The hooks in blackberry can trap woolly sheep, and make pruning and thinning in forests difficult.

How to tackle it

We control blackberry in our region's Key Native Ecosystems to protect each site’s unique plants and animals. You can control this pest on your property with these methods:

• Pull out – roots and all
  Dig out small patches all year round. Burn or dispose of roots (rhizomes) at a refuse transfer station. Find your local one here.
• Grazing
  Blackberry can be grazed by sheep and goats, especially in the seedling stage, and this can help suppress its growth. Goats fenced onto areas of blackberry or tethered near it can destroy plants completely.
• Stem scraping and paint
  To control small patches use undiluted glyphosate immediately after cutting from late summer to autumn. See Weedbusters for advice.
• Cut and paint stumps
  To control small patches use glyphosate (200ml/L to 500ml/L) immediately after cutting from late summer to autumn. See Weedbusters for advice.
• Spray
  In summer to autumn, before leaves become brittle, spray with herbicides. See Weedbusters for advice. Be sure to closely follow all label instructions.
• Biological control agents
  Blackberry rust (Phragmidium violaceum) will infect most plants and weaken them. Combined with insect damage to leaves and roots, this may be enough to reduce competitiveness in sites with high native plant numbers.
  The rust occurs more in autumn but can be seen any time of the year. In the summer the rust produces yellow spores and heavily infected leaves are killed.

How to stop it coming back

Blackberry can quickly return after slashing and grazing if roots (rhizomes) are left behind. When spraying regrowth, make sure stems are at least one metre long with fully expanded leaves as large leaves absorb herbicides more effectively.

Once the area is fully clear, plant and mulch to minimise regrowth and support local biodiversity – the plants and animals that naturally occur in the area.

Native species will usually overtop blackberry, so usually no control is needed except on the edges of planted areas.

If herbicides have been used, read the label for information about when to replant.

Check for regrowth at least every 4 months and continue to clear and spray if needed.

More information

• Weedbusters
• What to plant at your place
• Bionet - information about pests and disease in New Zealand