BLACKBERRY & FIRE

The use of fire to control blackberry is generally ineffective: even though stems are destroyed, the woody crown and root system are only slightly affected. Even after the intense wildfires in the ACT in 2003, officers from Parks, Conservation and Lands (PCL) found that regrowth occurred from root systems in the next year.

Researchers investigated whether the crown and root system were affected by the intensity of the fire. They chose a number of plots after the intense fires in Victoria in 2003. They found that all the blackberry plants survived the fire, but there was no simple relationship between blackberry recovery and pre-fire blackberry abundance.

In one plot there was a large number of crowns pre-fire but a low blackberry density two years later. One possible explanation for this is a combination of a hot fire and shallow stony soil; this would have reduced the blackberry roots to a few fragments and led to regrowth that was unable to compete successfully with native shrubs and trees establishing from seed.

In other plots, dense blackberry stands became established with little competition from natives. These plots have been farmland or had only sparse native vegetation cover where the native vegetation seed bank had been depleted before the fire.

The researchers suggested that an effective post-fire intervention may be to perform heavy seeding with native shrubs. This observation was echoed by PCL staff:

What we ideally need to be able to do is burn dead canes after we have sprayed them so we can plant or seed native plants. Otherwise we end up with weeds or eventually new blackberries growing among the protection of old dead canes.

PCL staff also noted that it was important to allow enough blackberry biomass to regenerate after a fire before the plants were treated with herbicides; otherwise the growing canes would not convey sufficient chemical to the crown and root system to kill them.